Pneumonia among adults hospitalized with laboratory-confirmed seasonal influenza virus infection-United States, 2005-2008

Characterisation of specific responses to three models of viral antigens in immunocompetent older adults

BACKGROUND

Memory responses to the antigens that an individual encounters throughout life may vary with the intensity and duration of antigen contacts or even with changes in immune status over time. This work aims to characterise specific responses to latent CMV, seasonal influenza and novel SARS-CoV-2 infections in immunocompetent individuals over 60 years of age. Specific cellular and humoral responses were identified by IFN-γ and granzyme B release by ELISpot and antibody level measurement. T lymphocyte subpopulation phenotypes were characterised by flow cytometry.

RESULTS

Cellular and humoral responses to these viruses were detected in almost all patients. Influenza and SARS-CoV-2 cellular responses were positively correlated. There was no significant correlation between CMV and influenza or SARS-CoV-2 responses although both were consistently lower in CMV-seropositive patients. CMV responses were negatively correlated with the levels of the least differentiated subsets of T lymphocytes, and positively correlated with the most differentiated ones, contrary to what happened with the influenza responses. Nevertheless, SARS-CoV-2 cellular responses were negatively correlated with the most differentiated CD8+ T lymphocytes, while humoral responses were negatively correlated with the least differentiated T lymphocytes. Responses to the three viruses were correlated with a Th1/Th2/Th17 balance in favour of Th1.

CONCLUSIONS

The results indicate that memory responses differ depending on the durability of the antigen stimulus. Cellular responses to novel pathogens resemble those generated by seasonal but not CMV infection. Subpopulation distribution and the level of specific T lymphocytes against previous pathogens could be used as immunocompetent status biomarkers in older adults reflecting their ability to generate memory responses to new pathogens.

Influence of Donor-Specific Characteristics on Cytokine Responses in H3N2 Influenza A Virus Infection: New Insights from an Ex Vivo Model

Influenza A virus (IAV) is known for causing seasonal epidemics ranging from flu to more severe outcomes like pneumonia, cytokine storms, and acute respiratory distress syndrome. The innate immune response and inflammasome activation play pivotal roles in sensing, preventing, and clearing the infection, as well as in the potential exacerbation of disease progression. This study examines the complex relationships between donor-specific characteristics and cytokine responses during H3N2 IAV infection using an ex vivo model. At 24 h post infection in 31 human lung explant tissue samples, key cytokines such as interleukin (IL)-6, IL-10, tumor necrosis factor-alpha (TNF-α), and interferon-gamma (IFN-γ) were upregulated. Interestingly, a history of lung cancer did not impact the acute immune response. However, cigarette smoking and programmed death-ligand 1 (PD-L1) expression on macrophages significantly increased IL-2 levels. Conversely, age inversely affected IL-4 levels, and diabetes mellitus negatively influenced IL-6 levels. Additionally, both diabetes mellitus and programmed cell death protein 1 (PD-1) expression on CD3+/CD4+ T cells negatively impacted TNF-α levels, while body mass index was inversely associated with IFN-γ production. Toll-like receptor 2 (TLR2) expression emerged as crucial in mediating acute innate and adaptive immune responses. These findings highlight the intricate interplay between individual physiological traits and immune responses during influenza infection, underscoring the importance of tailored and personalized approaches in IAV treatment and prevention.

Incidence of Influenza-related Medical Encounters and the Associated Healthcare Resource Use and Complications Across Adult Age Groups in the United States During the 2015-2020 Influenza Seasons

BACKGROUND

Research on influenza burden in adults has focused on crude subgroups with cut-points at 65 years, limiting insight into how burden varies with increasing age. This study describes the incidence of influenza-related outpatient visits, emergency room visits, and hospitalizations, along with healthcare resource use and complications in the aging adult population.

METHODS

Individuals aged ≥18 years in the United States were evaluated retrospectively in 5 seasonal cohorts (2015-2020 seasons) in strata of age with 5-year increments. Person-level electronic medical records linked to pharmacy and medical claims were used to ascertain patient characteristics and outcomes. Influenza-related medical encounters were identified based on diagnostic codes (International Classification of Diseases, 10th Edition, codes J09*-J11*).

RESULTS

Incidence of influenza-related outpatient visits was highest among people aged 18-34 years and declined with increasing age. For emergency room visits, incidence tended to be elevated for people aged 18-34 years, relatively stable from 35 through 60, and increased rapidly after age 60 years. Hospitalization incidence remained relatively stable until about 50 years of age and then increased with age. One in 3 patients was diagnosed with pneumonia after hospitalization, regardless of age. Across seasons, age groups, and clinical settings, on average, 40.8% of individuals were prescribed antivirals and 17.2% antibiotics.

CONCLUSIONS

Incidence of influenza-related hospitalizations begins to increase around age 50 years rather than the more common cut-point of 65, whereas incidence of outpatient visits was highest among younger adults. Influenza infections frequently led to antiviral and antibiotic prescriptions, underscoring the role influenza vaccination can play in combating antimicrobial resistance.

Influenza Vaccine Effectiveness Pre-pandemic Among Adults Hospitalized With Congestive Heart Failure or Chronic Obstructive Pulmonary Disease and Older Adults

BACKGROUND

Data are limited on influenza vaccine effectiveness (VE) in the prevention of influenza-related hospitalizations in older adults and those with underlying high-risk comorbidities.

METHODS

We conducted a prospective, test-negative, case-control study at 2 US hospitals from October 2018-March 2020 among adults aged ≥50 years hospitalized with acute respiratory illnesses (ARIs) and adults ≥18 years admitted with congestive heart failure (CHF) or chronic obstructive pulmonary disease (COPD) exacerbations. Adults were eligible if they resided in 1 of 8 counties in metropolitan Atlanta, Georgia. Nasopharyngeal and oropharyngeal swabs were tested using BioFire FilmArray (bioMérieux, Inc.) respiratory panel, and standard-of-care molecular results were included when available. Influenza vaccination history was determined from the Georgia vaccine registry and medical records. We used multivariable logistic regression to control for potential confounders and to determine 95% confidence intervals (CIs).

RESULTS

Among 3090 eligible adults, 1562 (50.6%) were enrolled. Of the 1515 with influenza vaccination history available, 701 (46.2%) had received vaccination during that season. Influenza was identified in 37 (5.3%) vaccinated versus 78 (9.6%) unvaccinated participants. After adjustment for age, race/ethnicity, immunosuppression, month, and season, pooled VE for any influenza-related hospitalization in the eligible study population was 63.1% (95% CI, 43.8-75.8%). Adjusted VE against influenza-related hospitalization for ARI in adults ≥50 years was 55.9% (29.9-72.3%) and adjusted VE against influenza-related CHF/COPD exacerbation in adults ≥18 years was 80.3% (36.3-93.9%).

CONCLUSIONS

Influenza vaccination was effective in preventing influenza-related hospitalizations in adults aged ≥50 years and those with CHF/COPD exacerbations during the 2018-2020 seasons.

Analysis of viral pneumonia and risk factors associated with severity of influenza virus infection in hospitalized patients from 2012 to 2016

BACKGROUND

Influenza viruses cause pneumonia in approximately one-third of cases, and pneumonia is an important cause of death. The aim was to identify risk factors associated with severity and those that could predict the development of pneumonia.

METHODS

This retrospective, observational study included all adult patients with confirmed influenza virus infection admitted to Son Espases University Hospital during four influenza seasons in Spain (October to May) from to 2012-2016.

RESULTS

Overall, 666 patients with laboratory-confirmed influenza were included, 93 (14%) of which were severe; 73 (10.9%) were admitted to Intensive Care Unit (ICU), 39 (5.8%) died, and 185 (27.7%) developed pneumonia. Compared to less severe cases, patients with severe disease: were less vaccinated (40% vs. 28%, p = 0.021); presented with more confusion (26.9% vs. 6.8%), were more hypoxemic (Horowitz index (PaO2/FiO2) 261 vs. 280), had higher C-reactive protein (CRP) (12.3 vs. 4.0), had more coinfections (26.8% vs. 6.3%) and had more pleural effusion (14% vs. 2.6%) (last six all p < 0.001). Risk factors significantly associated with severity were pneumonia [OR (95% CI) = 4.14 (2.4-7.16)], history of heart disease (1.84, 1.03-3.28), and confusion at admission (4.99, 2.55-9.74). Influenza vaccination was protective (0.53, 0.28-0.98). Compared to those without pneumonia, the pneumonia group had higher CRP (11.3 vs. 4.0, p < 0.001), lower oxygen saturation (92% vs. 94%, p < 0.001), were more hypoxic (PaO2/FiO2 266 vs. 281, p < 0.001), and incurred more mechanical ventilation, septic shock, admission to the ICU, and deaths (all four p < 0.001). Higher CRP and lower oxygen saturation were independent variables for predicting the development of pneumonia.

CONCLUSIONS

Pneumonia, history of heart disease, confusion and no influenza vaccination were independent variables to present complications in patients admitted with influenza infection.

Influenza and Viral Pneumonia

Influenza and other respiratory viruses are commonly identified in patients with community-acquired pneumonia, hospital-acquired pneumonia, and in immunocompromised patients with pneumonia. Clinically, it is difficult to differentiate viral from bacterial pneumonia. Similarly, the radiological findings of viral infection are in general nonspecific. The advent of polymerase chain reaction testing has enormously facilitated the identification of respiratory viruses, which has important implications for infection control measures and treatment. Currently, treatment options for patients with viral infection are limited but there is ongoing research on the development and clinical testing of new treatment regimens and strategies.

Impact of viral detection in patients with community-acquired pneumonia: An observational cohort study

PURPOSE

The presence of a respiratory virus in patients with community-acquired pneumonia (CAP) may have an impact on the bacterial etiology and clinical presentation. In this study we aimed to assess the role of viral infection in the bacterial etiology and outcomes of patients with CAP.

METHODS

We performed a retrospective study of all adults hospitalized with CAP between November 2017 and October 2018. Patients were classified according to the presence of viral infection. An unvaried and a multivaried analysis were performed to identify variables associated with viral infection and clinical outcomes.

RESULTS

Overall 590 patients were included. A microorganism was documented in 375 cases (63.5%). A viral infection was demonstrated in 118 (20%). The main pathogens were Streptococcus pneumoniae (35.8%), Staphylococcus aureus (2.9%) and influenza virus (10.8%). A trend to a higher rate of S. aureus (p=0.06) in patients with viral infection was observed. Patients with viral infection had more often bilateral consolidation patterns (17.8% vs 10.8%, p=0.04), respiratory failure (59.3% vs 42.8%, p=0.001), ICU admission (17.8% vs 7%, p=0.001) and invasive mechanical ventilation (9.3% vs 2.8%, p=0.003). Risk factors for respiratory failure were chronic lung disease, age >65 years, positive blood cultures and viral infection. Influenza, virus but no other respiratory viruses, was associated with respiratory failure (OR, 3.72; 95% CI, 2.06-6.73).

CONCLUSIONS

Our study reinforces the idea that co-viral infection has an impact in the clinical presentation of CAP causing a more severe clinical picture. This impact seems to be mainly due to influenza virus infection.

Impact of antiviral therapy on short- and long-term outcomes of patients with chronic obstructive pulmonary disease after influenza infection

Background

Respiratory complications often accompany influenza in patients with chronic obstructive pulmonary disease (COPD). In this retrospective study, we quantified the impact of antiviral therapy on exacerbations, healthcare resource utilization (HRU), and costs in patients with COPD across 5 influenza seasons.

Methods

Using claims data from US MarketScan® databases, we identified patients with COPD who had an influenza diagnosis during the 2012-2016 influenza seasons. Patients who received a neuraminidase inhibitor within 48 h of diagnosis (N = 4134) were identified and propensity score-matched 1:1 to a comparator cohort of untreated patients. We determined COPD- and pneumonia-related HRU and costs during month 1, each subsequent quarter, and months 2-13.

Results

Antiviral-treated patients had a significantly lower frequency of COPD-related outcomes than untreated patients during all periods (exacerbations: 10.4% vs 18.2% [month 1] and 17.7% vs 24.2% [months 2-13]; inpatient visit: 2.5% vs 7.9% [month 1] and 3.8% vs 6.7% [months 2-13]; P < 0.0001, all comparisons). Treated patients also had significantly lower outpatient and emergency department (ED) visits beyond month 1. Pneumonia-related inpatient, ED, and outpatient visits were significantly lower in antiviral-treated patients than in untreated patients over all periods (P < 0.0001, all comparisons). In all HRU categories, COPD- and pneumonia-related costs were significantly lower in treated patients over all periods (month-1 ED visit costs were higher).

Conclusions

Antiviral treatment in patients with COPD and influenza is associated with significantly lower HRU and costs in the postinfection month and for an entire year following infection compared with untreated patients.

Association of Chronic Medical Conditions With Severe Outcomes Among Nonpregnant Adults 18-49 Years Old Hospitalized With Influenza, FluSurv-NET, 2011-2019

Background

Older age and chronic conditions are associated with severe influenza outcomes; however, data are only comprehensively available for adults ≥65 years old. Using data from the Influenza Hospitalization Surveillance Network (FluSurv-NET), we identified characteristics associated with severe outcomes in adults 18-49 years old hospitalized with influenza.

Methods

We included FluSurv-NET data from nonpregnant adults 18-49 years old hospitalized with laboratory-confirmed influenza during the 2011-2012 through 2018-2019 seasons. We used bivariate and multivariable logistic regression to determine associations between select characteristics and severe outcomes including intensive care unit (ICU) admission, invasive mechanical ventilation (IMV), and in-hospital death.

Results

A total of 16 140 patients aged 18-49 years and hospitalized with influenza were included in the analysis; the median age was 39 years, and 26% received current-season influenza vaccine before hospitalization. Obesity, asthma, and diabetes mellitus were the most common chronic conditions. Conditions associated with a significantly increased risk of severe outcomes included age group 30-39 or 40-49 years (IMV, age group 30-39 years: adjusted odds ratio [aOR], 1.25; IMV, age group 40-49 years: aOR, 1.36; death, age group 30-39 years: aOR, 1.28; death, age group 40-49 years: aOR, 1.69), being unvaccinated (ICU: aOR, 1.18; IMV: aOR, 1.25; death: aOR, 1.48), and having chronic conditions including extreme obesity and chronic lung, cardiovascular, metabolic, neurologic, or liver diseases (ICU: range aOR, 1.22-1.56; IMV: range aOR, 1.17-1.54; death: range aOR, 1.43-2.36).

Conclusions

To reduce the morbidity and mortality associated with influenza among adults aged 18-49 years, health care providers should strongly encourage receipt of annual influenza vaccine and lifestyle/behavioral modifications, particularly among those with chronic medical conditions.

Pneumonia in newly diagnosed patients infected with the Omicron variant: a population-based study of Chinese patients in Chongqing

BACKGROUND

Pneumonia is the main complication of the Omicron variant of SARS-CoV-2; however, the incidence proportions and prognostic factors for Omicron-associated pneumonia have not been established. We conducted this study to characterise the incidence proportions and influence of various factors on prognosis of Omicron-associated pneumonia.

METHODS

We collected data from 714 patients infected with the Omicron variant in The First Affiliated Hospital of Chongqing Medical University (Chongqing, China) who were divided into different groups for analysis.

RESULTS

We identified 313 patients with Omicron-associated pneumonia at the time of diagnosis of patients infected with the Omicron variant, representing 43.8% of the entire cohort. A total of 82 were 15-59 years old, 71 were 60-69 years old, 76 were 70-79 years old and 84 were >80 years old. 133 were female and 180 were male. Incidence proportions of pneumonia were highest among patients with cardiovascular (82.4% of the basic disease of the cardiovascular system subset) or kidney disease (92.3% of the kidney disease subset), whereas patients with lung cancer (35.7% of the lung cancer subset) had a lower incidence proportion. Several factors were associated with the prognosis of pneumonia in patients infected with the Omicron variant. Patients with a thrombosis or pleural effusion had a longer hospitalisation time. Paxlovid and immunoglobulins improved the prognosis of patients with severe pneumonia. The following measures were significantly different in patients as a function of disease severity: number of neutrophils and lymphocytes, partial oxygen pressure; and myoglobin, lactic dehydrogenase, aspartate transaminase and procalcitonin levels.

CONCLUSION

Patients infected with the Omicron variant with coexisting cardiovascular or kidney disease, but not respiratory disease, had a higher incidence proportion of pneumonia. Paxlovid and immunoglobulins can be used in patients with severe infections to improve prognosis.

Aprotinin-Drug against Respiratory Diseases

Aprotinin (APR) was discovered in 1930. APR is an effective pan-protease inhibitor, a typical "magic shotgun". Until 2007, APR was widely used as an antithrombotic and anti-inflammatory drug in cardiac and noncardiac surgeries for reduction of bleeding and thus limiting the need for blood transfusion. The ability of APR to inhibit proteolytic activation of some viruses leads to its use as an antiviral drug for the prevention and treatment of acute respiratory virus infections. However, due to incompetent interpretation of several clinical trials followed by incredible controversy in the literature, the usage of APR was nearly stopped for a decade worldwide. In 2015-2020, after re-analysis of these clinical trials' data the restrictions in APR usage were lifted worldwide. This review discusses antiviral mechanisms of APR action and summarizes current knowledge and prospective regarding the use of APR treatment for diseases caused by RNA-containing viruses, including influenza and SARS-CoV-2 viruses, or as a part of combination antiviral treatment.

Factors Associated With the Development of Bacterial Pneumonia Related to Seasonal Influenza Virus Infection: A Study Using a Large-scale Health Insurance Claim Database

Background

Influenza-related bacterial pneumonia is a leading complication of influenza infection. However, the differences in the incidence rates and risk factors associated with concomitant viral/bacterial pneumonia (CP) and secondary bacterial pneumonia following influenza (SP) remain unclear. This study aimed to clarify the incidence rates of CP and SP following seasonal influenza and identify factors associated with their development.

Methods

This retrospective cohort study was conducted using the JMDC Claims Database, a health insurance claims database in Japan. All patients aged <75 years who developed influenza during 2 consecutive epidemic seasons, 2017/2018 and 2018/2019, were analyzed. CP was defined as bacterial pneumonia diagnosed between 3 days before and 6 days after the date of influenza diagnosis, and SP was defined as pneumonia diagnosed 7-30 days after the date of diagnosis. Multivariable logistic regression analyses were performed to identify factors associated with the development of CP and SP.

Results

Among the 10 473 014 individuals registered in the database, 1 341 355 patients with influenza were analyzed. The average age at diagnosis (SD) was 26.6 (18.6) years. There were 2901 (0.22%) and 1262 (0.09%) patients who developed CP and SP, respectively. Age 65-74 years, asthma, chronic bronchitis/emphysema, cardiovascular disease, renal disease, malignant tumor, and immunosuppression were significant risk factors for both CP and SP, whereas cerebrovascular disease, neurological disease, liver disease, and diabetes were risk factors specific to CP development.

Conclusions

The results determined the incidence rates of CP and SP and identified their risk factors, such as older age and comorbidities.

Neutrophils are gatekeepers of mucosal immunity

Mucosal tissues are constantly exposed to the outside environment. They receive signals from the commensal microbiome and tissue-specific triggers including alimentary and airborne elements and are tasked to maintain balance in the absence of inflammation and infection. Here, we present neutrophils as sentinel cells in mucosal immunity. We discuss the roles of neutrophils in mucosal homeostasis and overview clinical susceptibilities in patients with neutrophil defects. Finally, we present concepts related to specification of neutrophil responses within specific mucosal tissue microenvironments.

Respiratory viruses: their importance and lessons learned from COVID-19

Respiratory virus infection can cause severe illnesses capable of inducing acute respiratory failure that can progress rapidly to acute respiratory distress syndrome (ARDS). ARDS is related to poor outcomes, especially in individuals with a higher risk of infection, such as the elderly and those with comorbidities, i.e. obesity, asthma, diabetes mellitus and chronic respiratory or cardiovascular disease. Despite this, effective antiviral treatments available for severe viral lung infections are scarce. The coronavirus disease 2019 (COVID-19) pandemic demonstrated that there is also a need to understand the role of airborne transmission of respiratory viruses. Robust evidence supporting this exists, but better comprehension could help implement adequate measures to mitigate respiratory viral infections. In severe viral lung infections, early diagnosis, risk stratification and prognosis are essential in managing patients. Biomarkers can provide reliable, timely and accessible information possibly helpful for clinicians in managing severe lung viral infections. Although respiratory viruses highly impact global health, more research is needed to improve care and prognosis of severe lung viral infections. In this review, we discuss the epidemiology, diagnosis, clinical characteristics, management and prognosis of patients with severe infections due to respiratory viruses.

Epidemiology, Clinical Characteristics, and Outcomes of Influenza-Associated Hospitalizations in US Children Over 9 Seasons Following the 2009 H1N1 Pandemic

BACKGROUND

Recent population-based data are limited regarding influenza-associated hospitalizations in US children.

METHODS

We identified children <18 years hospitalized with laboratory-confirmed influenza during 2010-2019 seasons, through the Centers for Disease Control and Prevention's Influenza Hospitalization Surveillance Network. Adjusted hospitalization and in-hospital mortality rates were calculated, and multivariable logistic regression was conducted to evaluate risk factors for pneumonia, intensive care unit (ICU) admission, mechanical ventilation, and death.

RESULTS

Over 9 seasons, adjusted influenza-associated hospitalization incidence rates ranged from 10 to 375 per 100 000 persons each season and were highest among infants <6 months old. Rates decreased with increasing age. The highest in-hospital mortality rates were observed in children <6 months old (0.73 per 100 000 persons). Over time, antiviral treatment significantly increased, from 56% to 85% (P < .001), and influenza vaccination rates increased from 33% to 44% (P = .003). Among the 13 235 hospitalized children, 2676 (20%) were admitted to the ICU, 2262 (17%) had pneumonia, 690 (5%) required mechanical ventilation, and 72 (0.5%) died during hospitalization. Compared with those <6 months of age, hospitalized children ≥13 years old had higher odds of pneumonia (adjusted odds ratio, 2.7 [95% confidence interval, 2.1-3.4], ICU admission (1.6 [1.3-1.9]), mechanical ventilation (1.6 [1.1-2.2]), and death (3.3 [1.2-9.3]).

CONCLUSIONS

Hospitalization and death rates were greatest in younger children at the population level. Among hospitalized children, however, older children had a higher risk of severe outcomes. Continued efforts to prevent and attenuate influenza in children are needed.

Influenza A virus NS1 protein represses antiviral immune response by hijacking NF-κB to mediate transcription of type III IFN

Background

Non-structural protein 1 (NS1), one of the viral proteins of influenza A viruses (IAVs), plays a crucial role in evading host antiviral immune response. It is known that the IAV NS1 protein regulates the antiviral genes response mainly through several different molecular mechanisms in cytoplasm. Current evidence suggests that NS1 represses the transcription of IFNB1 gene by inhibiting the recruitment of Pol II to its exons and promoters in infected cells. However, IAV NS1 whether can utilize a common mechanism to antagonize antiviral response by interacting with cellular DNA and immune-related transcription factors in the nucleus, is not yet clear.

Methods

Chromatin immunoprecipitation and sequencing (ChIP-seq) was used to determine genome-wide transcriptional DNA-binding sites for NS1 and NF-κB in viral infection. Next, we used ChIP-reChIP, luciferase reporter assay and secreted embryonic alkaline phosphatase (SEAP) assay to provide information on the dynamic binding of NS1 and NF-κB to chromatin. RNA sequencing (RNA-seq) transcriptomic analyses were used to explore the critical role of NS1 and NF-κB in IAV infection as well as the detailed processes governing host antiviral response.

Results

Herein, NS1 was found to co-localize with NF-κB using ChIP-seq. ChIP-reChIP and luciferase reporter assay confirmed the co-localization of NS1 and NF-κB at type III IFN genes, such as IFNL1, IFNL2, and IFNL3. We discovered that NS1 disturbed binding manners of NF-κB to inhibit IFNL1 expression. NS1 hijacked NF-κB from a typical IFNL1 promoter to the exon-intron region of IFNL1 and decreased the enrichment of RNA polymerase II and H3K27ac, a chromatin accessibility marker, in the promoter region of IFNL1 during IAV infection, consequently reducing IFNL1 gene expression. NS1 deletion enhanced the enrichment of RNA polymerase II at the IFNL1 promoter and promoted its expression.

Conclusion

Overall, NS1 hijacked NF-κB to prevent its interaction with the IFNL1 promoter and restricted the open chromatin architecture of the promoter, thereby abating antiviral gene expression.

Neutrophil subsets and their differential roles in viral respiratory diseases

Neutrophils play significant roles in immune homeostasis and as neutralizers of microbial infections. Recent evidence further suggests heterogeneity of neutrophil developmental and activation states that exert specialized effector functions during inflammatory disease conditions. Neutrophils can play multiple roles during viral infections, secreting inflammatory mediators and cytokines that contribute significantly to host defense and pathogenicity. However, their roles in viral immunity are not well understood. In this review, we present an overview of neutrophil heterogeneity and its impact on the course and severity of viral respiratory infectious diseases. We focus on the evidence demonstrating the crucial roles neutrophils play in the immune response toward respiratory infections, using influenza as a model. We further extend the understanding of neutrophil function with the studies pertaining to COVID-19 disease and its neutrophil-associated pathologies. Finally, we discuss the relevance of these results for future therapeutic options through targeting and regulating neutrophil-specific responses.

[Viral pneumonia. COVID-19 pneumonia]

Viruses are becoming more and more important as etiological agents of pneumonia, mainly due to improvements in diagnostic techniques. At present, they account for approximately one-third of community-acquired pneumonia cases. They tend to occur in children and elderly patients, causing anything from mild cases to severe cases which require intubation and intensive care. The main causative agents include rhinovirus, influenza virus A or B, metapneumovirus, respiratory syncytial virus, parainfluenza virus, coronavirus, or adenovirus. Infection produced by SARS-CoV-2, the cause of the current COVID-19 pandemic, which has had devastating consequences, is proof of the vital importance of viral pneumonia. This is the main subject of this update. Drawing on the abundant information available, which has been continuously evolving since the beginning of the pandemic, this section will review the main characteristics of the virus, its pathophysiology, and its clinical manifestations as well as the main diagnostic and treatment methods.

Severe Infections Due to Respiratory Viruses

Severe viral infections may result in severe illnesses capable of causing acute respiratory failure that could progress rapidly to acute respiratory distress syndrome (ARDS), related to worse outcomes, especially in individuals with a higher risk of infection, including the elderly and those with comorbidities such as asthma, diabetes mellitus and chronic respiratory or cardiovascular disease. In addition, in cases of severe viral pneumonia, co-infection with bacteria such as Streptococcus pneumoniae and Staphylococcus aureus is related to worse outcomes. Respiratory viruses like influenza, rhinovirus, parainfluenza, adenovirus, metapneumovirus, respiratory syncytial virus, and coronavirus have increasingly been detected. This trend has become more prevalent, especially in critically ill patients, due to the availability and implementation of molecular assays in clinical practice. Respiratory viruses have been diagnosed as a frequent cause of severe pneumonia, including cases of community-acquired pneumonia, hospital-acquired pneumonia, and ventilator-associated pneumonia. In this review, we will discuss the epidemiology, diagnosis, clinical characteristics, management, and prognosis of patients with severe infections due to respiratory viruses, with a focus on influenza viruses, non-influenza viruses, and coronaviruses.

Characteristics and Outcomes of Hospitalized Pregnant Women With Influenza, 2010 to 2019 : A Repeated Cross-Sectional Study

BACKGROUND

Pregnant women may be at increased risk for severe influenza-associated outcomes.

OBJECTIVE

To describe characteristics and outcomes of hospitalized pregnant women with influenza.

DESIGN

Repeated cross-sectional study.

SETTING

The population-based U.S. Influenza Hospitalization Surveillance Network during the 2010-2011 through 2018-2019 influenza seasons.

PATIENTS

Pregnant women (aged 15 to 44 years) hospitalized with laboratory-confirmed influenza identified through provider-initiated or facility-based testing practices.

MEASUREMENTS

Clinical characteristics, interventions, and in-hospital maternal and fetal outcomes were obtained through medical chart abstraction. Multivariable logistic regression was used to evaluate the association between influenza A subtype and severe maternal influenza-associated outcomes, including intensive care unit (ICU) admission, mechanical ventilation, extracorporeal membrane oxygenation, or in-hospital death.

RESULTS

Of 9652 women aged 15 to 44 years and hospitalized with influenza, 2690 (27.9%) were pregnant. Among the 2690 pregnant women, the median age was 28 years, 62% were in their third trimester, and 42% had at least 1 underlying condition. Overall, 32% were vaccinated against influenza and 88% received antiviral treatment. Five percent required ICU admission, 2% required mechanical ventilation, and 0.3% (n = 8) died. Pregnant women with influenza A H1N1 were more likely to have severe outcomes than those with influenza A H3N2 (adjusted risk ratio, 1.9 [95% CI, 1.3 to 2.8]). Most women (71%) were still pregnant at hospital discharge. Among 754 women who were no longer pregnant at discharge, 96% had a pregnancy resulting in live birth, and 3% experienced fetal loss.

LIMITATION

Maternal and fetal outcomes that occurred after hospital discharge were not captured.

CONCLUSION

Over 9 influenza seasons, one third of reproductive-aged women hospitalized with influenza were pregnant. Influenza A H1N1 was associated with more severe maternal outcomes. Pregnant women remain a high-priority target group for vaccination.

PRIMARY FUNDING SOURCE

Centers for Disease Control and Prevention.

Clinical efficacy and safety of high dose trivalent influenza vaccine in adults and immunosuppressed populations - A systematic review and meta-analysis

OBJECTIVES

Influenza is associated with significant morbidity and mortality, especially in older and immunocompromised patients. Few data are available on the clinical benefit of high dose trivalent influenza vaccine (TIV). We aimed to assess the clinical efficacy and safety of high dose TIV.

METHODS

We conducted a systematic review and meta-analysis of randomized controlled trials (RCTs), evaluating high dose versus standard dose TIV for prevention of seasonal influenza in adult population. Primary outcome was laboratory-confirmed influenza. Subgroups analyses included older adults and immunocompromised patients.

RESULTS

We included 16 trials, 47,857 patients; 10 included older adults and three immunocompromised patients. Laboratory confirmed influenza was significantly reduced with high dose TIV (relative risk 0.76, 95% confidence interval 0.64 to 0.9). This outcome stemmed mainly from one trial in older adults. Specifically, A(H3N2) laboratory confirmed influenza, but not A(H1N1) or B lineages, was reduced. No difference in mortality or hospitalizations was demonstrated. Immunological response was significantly higher with high dose vaccine. Serious adverse events were significantly less common in the high dose group.

CONCLUSIONS

High dose TIV lowers the rates of laboratory confirmed influenza, mainly A (H3N2), in older adults vs. standard dose. Further studies should address immunocompromised patients and report clinical outcomes.

The Mechanism behind Influenza Virus Cytokine Storm

Influenza viruses are still a serious threat to human health. Cytokines are essential for cell-to-cell communication and viral clearance in the immune system, but excessive cytokines can cause serious immune pathology. Deaths caused by severe influenza are usually related to cytokine storms. The recent literature has described the mechanism behind the cytokine-storm network and how it can exacerbate host pathological damage. Biological factors such as sex, age, and obesity may cause biological differences between different individuals, which affects cytokine storms induced by the influenza virus. In this review, we summarize the mechanism behind influenza virus cytokine storms and the differences in cytokine storms of different ages and sexes, and in obesity.

Use of Procalcitonin and a Respiratory Polymerase Chain Reaction Panel to Reduce Antibiotic Use via an Electronic Medical Record Alert

Background

Respiratory tract infections are often viral and but are frequently treated with antibiotics, providing a significant opportunity for antibiotic de-escalation in patients. We sought to determine whether an automated electronic medical record best practice alert (BPA) based on procalcitonin and respiratory polymerase chain reaction (PCR) results could help reduce inappropriate antibiotic use in patients with likely viral respiratory illness.

Methods

This multisite, pre–post, quasi-experimental study included patients 18 years and older with a procalcitonin level <0.25 ng/mL and a virus identified on respiratory PCR within 48 hours of each other, and 1 or more systemic antibiotics ordered. In the study group, a BPA alerted providers of the diagnostic results suggesting viral infection and prompted them to reassess the need for antibiotics. The primary outcome measured was total antibiotic-days of therapy.

Results

The BPA reduced inpatient antibiotic-days of therapy by a mean of 2.2 days compared with patients who met criteria but did not have the alert fire (8.0 vs 5.8 days, respectively, P < .001). The BPA also reduced the percentage of patients prescribed antibiotics on discharge (20% vs 47.8%, P < .001), whereas there was no difference in need for antibiotic escalation after initial discontinuation (7.6% vs 4.3%, P = .198).

Conclusions

The automated antimicrobial stewardship BPA effectively reduced antibiotic use and discharge prescribing rates when diagnostics suggested viral respiratory tract infection, without a higher rate for reinitiation of antibiotics after discontinuation.

Clinical Features and Outcomes of Community-Acquired Pneumonia Caused by Haemophilus Influenza

Background

Long regarded as the second most common cause of community-acquired pneumonia (CAP), Haemophilus influenzae has recently been identified with almost equal frequency as pneumococcus in patients hospitalized for CAP. The literature lacks a detailed description of the presentation, clinical features, laboratory and radiologic findings, and outcomes in Haemophilus pneumonia.

Methods

During 2 prospective studies of patients hospitalized for CAP, we identified 33 patients with Haemophilus pneumonia. In order to provide context, we compared clinical findings in these patients with findings in 36 patients with pneumococcal pneumonia identified during the same period. We included and analyzed separately data from patients with viral coinfection. Patients with coinfection by other bacteria were excluded.

Results

Haemophilus pneumonia occurred in older adults who had underlying chronic lung disease, cardiac conditions, and alcohol use disorder, the same population at risk for pneumococcal pneumonia. However, in contrast to pneumococcal pneumonia, patients with Haemophilus pneumonia had less severe infection as shown by absence of septic shock on admission, less confusion, fewer cases of leukopenia or extreme leukocytosis, and no deaths at 30 days. Viral coinfection greatly increased the severity of Haemophilus, but not pneumococcal pneumonia.

Conclusions

We present the first thorough description of Haemophilus pneumonia, show that it is less severe than pneumococcal pneumonia, and document that viral coinfection greatly increases its severity. These distinctions are lost when the label CAP is liberally applied to all patients who come to the hospital from the community for pneumonia.

Situational assessment of adult vaccine preventable disease and the potential for immunization advocacy and policy in low- and middle-income countries

By 2050, the number of adults over 65 years of age will be double the under-5 population, and heavily concentrated in low- and middle-income countries. Population growth and increasing life expectancies call for effective healthy aging strategies inclusive of immunization to reduce the burden of vaccine-preventable diseases, improve quality of life, and mitigate antimicrobial resistance. Based on a review of available literature on the pneumococcal disease, influenza, and herpes zoster epidemiology and economic burden, and the health systems and policy barriers for adult immunization, we identified evidence gaps and considerations for prioritizing adult immunization. The body of evidence for adult immunization and the health and economic burden of adult disease is heavily concentrated in high-income countries. The few countries reporting adult immunization policies generally focus on high-risk groups. Despite robust child immunization programs in most countries, adult immunization programs and policies lag far behind and there is a general lack of appropriate delivery platforms. Global adult disease burden and economic costs are substantial but evidence from low- and middle-income countries is limited. There is a need for a strengthened evidence base and political commitment to drive a comprehensive, global technical consensus on adult immunization.

Risk Factors for Pneumonia and Death in Adult Patients With Seasonal Influenza and Establishment of Prediction Scores: A Population-Based Study

Background

Seasonal influenza remains a global health problem; however, there are limited data on the specific relative risks for pneumonia and death among outpatients considered to be at high risk for influenza complications. This population-based study aimed to develop prediction models for determining the risk of influenza-related pneumonia and death.

Methods

We included patients diagnosed with laboratory-confirmed influenza between 2016 and 2017 (main cohort, n = 25 659), those diagnosed between 2015 and 2016 (validation cohort 1, n = 16 727), and those diagnosed between 2017 and 2018 (validation cohort 2, n = 34 219). Prediction scores were developed based on the incidence and independent predictors of pneumonia and death identified using multivariate analyses, and patients were categorized into low-, medium-, and high-risk groups based on total scores.

Results

In the main cohort, age, gender, and certain comorbidities (dementia, congestive heart failure, diabetes, and others) were independent predictors of pneumonia and death. The 28-day pneumonia incidence was 0.5%, 4.1%, and 10.8% in the low-, medium-, and high-risk groups, respectively (c-index, 0.75); the 28-day mortality was 0.05%, 0.7%, and 3.3% in the low-, medium-, and high-risk groups, respectively (c-index, 0.85). In validation cohort 1, c-indices for the models for pneumonia and death were 0.75 and 0.87, respectively. In validation cohort 2, c-indices for the models were 0.74 and 0.87, respectively.

Conclusions

We successfully developed and validated simple-to-use risk prediction models, which would promptly provide useful information for treatment decisions in primary care settings.

Obesity as a contributor to immunopathology in pregnant and non-pregnant adults with COVID-19

The ongoing coronavirus disease 2019 (COVID-19) pandemic has led to a global public health emergency with the need to identify vulnerable populations who may benefit from increased screening and healthcare resources. Initial data suggest that overall, pregnancy is not a significant risk factor for severe coronavirus disease 2019 (COVID-19). However, case series have suggested that maternal obesity is one of the most important comorbidities associated with more severe disease. In obese individuals, suppressors of cytokine signaling are upregulated and type I and III interferon responses are delayed and blunted leading to ineffective viral clearance. Obesity is also associated with changes in systemic immunity involving a wide range of immune cells and mechanisms that lead to low-grade chronic inflammation, which can compromise antiviral immunity. Macrophage activation in adipose tissue can produce low levels of pro-inflammatory cytokines (TNF-α, IL-1β, IL-6). Further, adipocyte secretion of leptin is pro-inflammatory and high circulating levels of leptin have been associated with mortality in patients with acute respiratory distress syndrome. The synergistic effects of obesity-associated delays in immune control of COVID-19 with mechanical stress of increased adipose tissue may contribute to a greater risk of pulmonary compromise in obese pregnant women. In this review, we bring together data regarding obesity as a key co-morbidity for COVID-19 in pregnancy with known changes in the antiviral immune response associated with obesity. We also describe how the global burden of obesity among reproductive age women has serious public health implications for COVID-19.

Factors Affecting the Incidence of Hospitalized Pneumonia after Influenza Infection in Korea Using the National Health Insurance Research Database, 2014-2018: Focusing on the Effect of Antiviral Therapy in the 2017 Flu Season

BACKGROUND

This study aimed to investigate the effect of antiviral therapy following influenza outpatient episodes on the incidence of hospitalized pneumonia episodes, one of secondary complications of influenza.

METHODS

In the National Health Insurance Research Database, data from July 2013 to June 2018 were used. All of the claim data with diagnoses of influenza and pneumonia were converted to episodes of care after applying 100 days of window period. With the 100-day episodes of care, the characteristics of influenza outpatient episodes and antiviral therapy for influenza, the incidence of hospitalized pneumonia episodes following influenza, and the effect of antiviral therapy for influenza on hospitalized pneumonia episodes were investigated.

RESULTS

The crude incidence rate of hospitalized pneumonia after influenza infection was 0.57% in both males and females. Factors affecting hospitalized pneumonia included age, income level except self-employed highest (only in females), municipality, medical institution type, precedent chronic diseases except hepatitis (only in females) and antiviral therapy. In the 2017 flu season, the relative risk was 0.38 (95% confidence interval [CI], 0.29-0.50) in males aged 0-9 and 0.43 (95% CI, 0.32-0.57) in females aged 0-9 without chronic diseases, and it was 0.51 (95% CI, 0.42-0.61) in males aged 0-9 and 0.42 (95% CI, 0.35-0.50) in females aged 0-9 with one or more chronic diseases in the aspect of the effect of antiviral therapy on pneumonia. It suggests that antiviral therapy may decrease the incidence of pneumonia after influenza infection.

CONCLUSION

After outpatient episode incidence of influenza, antiviral treatment has been shown to reduce the incidence of hospitalized pneumonia, especially in infants and children, during pandemic season 2017. Antiviral therapy for influenza is recommended to minimize burden caused by influenza virus infection and to reduce pneumonia. In addition, medical costs of hospitalization may decrease by antiviral therapy, especially in infants and children.

The Power of First Impressions: Can Influenza Imprinting during Infancy Inform Vaccine Design?

Influenza virus infection causes severe respiratory illness in people worldwide, disproportionately affecting infants. The immature respiratory tract coupled with the developing immune system, and lack of previous exposure to the virus is thought to synergistically play a role in the increased disease severity in younger age groups. No influenza vaccines are available for those under six months, although maternal influenza immunization is recommended. In children aged six months to two years, vaccine immunogenicity is dampened compared to older children and adults. Unlike older children and adults, the infant immune system has fewer antigen-presenting cells and soluble immune factors. Paradoxically, we know that a person's first infection with the influenza virus during infancy or childhood leads to the establishment of life-long immunity toward that particular virus strain. This is called influenza imprinting. We contend that by understanding the influenza imprinting event in the context of the infant immune system, we will be able to design more effective influenza vaccines for both infants and adults. Working through the lens of imprinting, using infant influenza animal models such as mice and ferrets which have proven useful for infant immunity studies, we will gain a better understanding of imprinting and its implications regarding vaccine design. This review examines literature regarding infant immune and respiratory development, current vaccine strategies, and highlights the importance of research into the imprinting event in infant animal models to develop more effective and protective vaccines for all including young children.

Normal Respiratory Flora as a Cause of Community-Acquired Pneumonia

Background

Intensive studies have failed to identify an etiologic agent in >50% cases of community-acquired pneumonia (CAP). Bacterial pneumonia follows aspiration of recognized bacterial pathogens (RBPs) such as Streptococcus pneumoniae, Haemophilus influenzae, and Staphylococcus aureus after they have colonize the nasopharynx. We hypothesized that aspiration of normal respiratory flora (NRF) might also cause CAP.

Methods

We studied 120 patients hospitalized for CAP who provided a high-quality sputum specimen at, or soon after admission, using Gram stain, quantitative sputum culture, bacterial speciation by matrix-assisted laser desorption ionization time-of-flight, and viral polymerase chain reaction. Thresholds for diagnosis of bacterial infection were ≥10⁵ colony-forming units (cfu)/mL sputum for RBPs and ≥10⁶ cfu for NRF.

Results

Recognized bacterial pathogens were found in 68 of 120 (56.7%) patients; 14 (20.1%) of these had a coinfecting respiratory virus. Normal respiratory flora were found in 31 (25.8%) patients; 10 (32.2%) had a coinfecting respiratory virus. Infection by ≥2 RBPs occurred in 10 cases and by NRF together with RBPs in 13 cases. Among NRF, organisms identified as Streptococcus mitis, which share many genetic features of S pneumoniae, predominated. A respiratory virus alone was found in 16 of 120 (13.3%) patients. Overall, an etiologic diagnosis was established in 95.8% of cases.

Conclusions

Normal respiratory flora, with or without viral coinfection, appear to have caused one quarter of cases of CAP and may have played a contributory role in an additional 10.8% of cases caused by RBPs. An etiology for CAP was identified in >95% of patients who provided a high-quality sputum at, or soon after, the time of admission.

Outcome of Critically Ill Patients With Influenza Infection: A Retrospective Study

Background

Influenza causes significant morbidity and mortality in adults, and numerous patients require intensive care unit (ICU) admission. Acute respiratory distress syndrome (ARDS) is clearly described in this context, but other clinical presentations exist that need to be assessed for incidence and outcome. The primary goal of this study was to describe the characteristics of patients admitted in ICU for influenza, their clinical presentation, and the 3-month mortality rate. The second objective was to search for 3-month mortality risk factors.

Methods

This is a retrospective study including all patients admitted to 3 ICUs due to influenza-related disease between October 2013 and June 2016, which assesses the 3-month mortality rate. We compared clinical presentation, biological data, and outcome at 3 months between survivors and non-survivors. We created a predicting 3-month mortality model with Classification and Regression Tree analysis.

Results

Sixty-nine patients were included, 50 patients (72.5%) for ARDS, 5 (7.2%) for myocarditis, and 14 (20.3%) for acute respiratory failure without ARDS criteria. Non-typed influenza A was found in 30 cases (43.5%), influenza A H1N1 in 18 (26.1%), H3N2 in 3 (4.3%), and influenza B in 18 cases (27.5%). The 3-month mortality rate was 29% (n = 20). Extracorporeal membrane oxygenation (ECMO) was implanted in 23 patients, without any significant increase in mortality (39% vs 24% without ECMO, P = .19). A creatinine serum superior to 96 μmol/L, an aspartate aminotransferase level superior to 68 UI/L, and a Pao₂/Fio₂ ration below 110 were associated with 3-month mortality in our predictive mortality model.

Conclusion

Influenza in ICUs may have several clinical presentations. The mortality rate is high, but ECMO may be an effective rescue therapy.

Clinical Features and Outcomes of Immunocompromised Children Hospitalized With Laboratory-Confirmed Influenza in the United States, 2011-2015

BACKGROUND

Existing data on the clinical features and outcomes of immunocompromised children with influenza are limited.

METHODS

Data from the 2011-2012 through 2014-2015 influenza seasons were collected as part of the Centers for Disease Control and Prevention (CDC) Influenza Hospitalization Surveillance Network (FluSurv-NET). We compared clinical features and outcomes between immunocompromised and nonimmunocompromised children (<18 years old) hospitalized with laboratory-confirmed community-acquired influenza. Immunocompromised children were defined as those for whom ≥1 of the following applies: human immunodeficiency virus/acquired immunodeficiency syndrome, cancer, stem cell or solid organ transplantation, nonsteroidal immunosuppressive therapy, immunoglobulin deficiency, complement deficiency, asplenia, and/or another rare condition. The primary outcomes were intensive care admission, duration of hospitalization, and in-hospital death.

RESULTS

Among 5262 hospitalized children, 242 (4.6%) were immunocompromised; receipt of nonsteroidal immunosuppressive therapy (60%), cancer (39%), and solid organ transplantation (14%) were most common. Immunocompromised children were older than the nonimmunocompromised children (median, 8.8 vs 2.8 years, respectively; P < .001), more likely to have another comorbidity (58% vs 49%, respectively; P = .007), and more likely to have received an influenza vaccination (58% vs 39%, respectively; P < .001) and early antiviral treatment (35% vs 27%, respectively; P = .013). In multivariable analyses, immunocompromised children were less likely to receive intensive care (adjusted odds ratio [95% confidence interval], 0.31 [0.20-0.49]) and had a slightly longer duration of hospitalization (adjusted hazard ratio of hospital discharge [95% confidence interval], 0.89 [0.80-0.99]). Death was uncommon in both groups.

CONCLUSIONS

Immunocompromised children hospitalized with influenza received intensive care less frequently but had a longer hospitalization duration than nonimmunocompromised children. Vaccination and early antiviral use could be improved substantially. Data are needed to determine whether immunocompromised children are more commonly admitted with milder influenza severity than are nonimmunocompromised children.

Influenza Infections and Emergent Viral Infections in Intensive Care Unit

Critically ill patients are admitted to an intensive care unit (ICU) for multiple reasons. In this study, we aim to analyze the current evidence and findings associated with influenza and other emergent viral infections, namely, herpes simplex virus type 1 (HSV-1), Epstein-Barr virus (EBV), and cytomegalovirus (CMV).

Among medical conditions, community-acquired respiratory infections are the most frequent reason for ventilatory support in ICUs. Community-acquired pneumonia in a severe form including the need of invasive mechanical ventilation and/or vasopressors is associated with high mortality rates. However, after the pandemic that occurred in 2009 by H1N1 influenza, the number of cases being admitted to ICUs with viral infections is on the rise. Patients in whom an etiology would not have been identified in the past are currently being tested with more sensitive viral molecular diagnostic tools, and patients being admitted to ICUs have more preexisting medical conditions that can predispose to viral infections. Viral infections can trigger the dysregulation of the immune system by inducing a massive cytokine response. This cytokine storm can cause endothelial damage and dysfunction, deregulation of coagulation, and, consequently, alteration of microvascular permeability, tissue edema, and shock. In severe influenza, this vascular hyperpermeability can lead to acute lung injury, multiorgan failure, and encephalopathy. In immunocompetent patients, the most common viral infections are respiratory, and influenza should be considered in patients with severe respiratory failure being admitted to ICU. Seasonality and coinfection are two important features when considering influenza as a pathogen in critically ill patients.

Herpesviridae (HSV, CMV, and EBV) may reactivate in ICU patients, and their reactivation is associated with morbidity/mortality. However, whether a specific treatment may impact on outcome remains to be determined.

The challenges of influenza for public health

Influenza, an infectious disease of the respiratory system, represents a major burden for public health. This disease affects all age groups with different prognosis, being life threatening for vulnerable individuals. Despite influenza being a vaccine-preventable disease, the control of the infection needs annual vaccination campaigns and constant improvements. Herein, the main challenges of influenza in relation to the pathogenic agent, the available vaccines and the health impact identified during the Light on Vax event, an expert meeting organized by the Asociación Española de Vacunología [Spanish Vaccinology Association] (AEV), are reported. Further possible steps in the control of influenza are also suggested. Ideally, the development of innovative and universal vaccines that would confer life-lasting and broader-spectrum immunity is highly desirable.

Influenza virus-related critical illness: pathophysiology and epidemiology

Influenza virus affects the respiratory tract by direct viral infection or by damage from the immune system response. In humans, the respiratory epithelium is the only site where the hemagglutinin (HA) molecule is effectively cleaved, generating infectious virus particles. Virus transmission occurs through a susceptible individual's contact with aerosols or respiratory fomites from an infected individual. The inability of the lung to perform its primary function of gas exchange can result from multiple mechanisms, including obstruction of the airways, loss of alveolar structure, loss of lung epithelial integrity from direct epithelial cell killing, and degradation of the critical extracellular matrix.Approximately 30-40% of hospitalized patients with laboratory-confirmed influenza are diagnosed with acute pneumonia. These patients who develop pneumonia are more likely to be < 5 years old, > 65 years old, Caucasian, and nursing home residents; have chronic lung or heart disease and history of smoking, and are immunocompromised.Influenza can primarily cause severe pneumonia, but it can also present in conjunction with or be followed by a secondary bacterial infection, most commonly by Staphylococcus aureus and Streptococcus pneumoniae. Influenza is associated with a high predisposition to bacterial sepsis and ARDS. Viral infections presenting concurrently with bacterial pneumonia are now known to occur with a frequency of 30-50% in both adult and pediatric populations. The H3N2 subtype has been associated with unprecedented high levels of intensive care unit (ICU) admission.Influenza A is the predominant viral etiology of acute respiratory distress syndrome (ARDS) in adults. Risk factors independently associated with ARDS are age between 36 and 55 years old, pregnancy, and obesity, while protective factors are female sex, influenza vaccination, and infections with Influenza A (H3N2) or Influenza B viruses.In the ICU, particularly during the winter season, influenza should be suspected not only in patients with typical symptoms and epidemiology, but also in patients with severe pneumonia, ARDS, sepsis with or without bacterial co-infection, as well as in patients with encephalitis, myocarditis, and rhabdomyolysis.

Age-Related Differences in Hospitalization Rates, Clinical Presentation, and Outcomes Among Older Adults Hospitalized With Influenza-U.S. Influenza Hospitalization Surveillance Network (FluSurv-NET)

BACKGROUND

Rates of influenza hospitalizations differ by age, but few data are available regarding differences in laboratory-confirmed rates among adults aged ≥65 years.

METHODS

We evaluated age-related differences in influenza-associated hospitalization rates, clinical presentation, and outcomes among 19 760 older adults with laboratory-confirmed influenza at 14 FluSurv-NET sites during the 2011-2012 through 2014-2015 influenza seasons using 10-year age groups.

RESULTS

There were large stepwise increases in the population rates of influenza hospitalization with each 10-year increase in age. Rates ranged from 101-417, 209-1264, and 562-2651 per 100 000 persons over 4 influenza seasons in patients aged 65-74 years, 75-84 years, and ≥85 years, respectively. Hospitalization rates among adults aged 75-84 years and ≥85 years were 1.4-3.0 and 2.2-6.4 times greater, respectively, than rates for adults aged 65-74 years. Among patients hospitalized with laboratory-confirmed influenza, there were age-related differences in demographics, medical histories, and symptoms and signs at presentation. Compared to hospitalized patients aged 65-74 years, patients aged ≥85 years had higher odds of pneumonia (aOR, 1.2; 95% CI, 1.0-1.3; P = .01) and in-hospital death or transfer to hospice (aOR, 2.1; 95% CI, 1.7-2.6; P < .01).

CONCLUSIONS

Age-related differences in the incidence and severity of influenza hospitalizations among adults aged ≥65 years can inform prevention and treatment efforts, and data should be analyzed and reported using additional age strata.

Respiratory syncytial virus, human metapneumovirus, and influenza virus infection in Bangkok, 2016-2017

Children and adults residing in densely populated urban centers around the world are at risk of seasonal influenza-like illness caused by respiratory viruses such as influenza virus, human metapneumovirus (hMPV), and respiratory syncytial virus (RSV). In a large metropolitan of Thailand’s capital city Bangkok, most respiratory infections are rarely confirmed by molecular diagnostics. We therefore examined the frequency of RSV, hMPV, and influenza virus in 8,842 patients who presented influenza-like illness and sought medical care at a large hospital in Bangkok between 2016 and 2017. Using a multiplex real-time reverse-transcription polymerase chain reaction (RT-PCR), 30.5% (2,699/8,842) of nasopharyngeal (NP) swab samples tested positive for one or more of these viruses. Influenza virus comprised 17.3% (1,528/8,842), of which the majority were influenza A/H3N2. Such infection was most prevalent among adults and the elderly. RSV was identified in 11.4% (1,011/8,842) and were mostly ON1 and BA9 genotypes. Of the hMPV-positive samples (3.6%, 318/8,842), genotypes A2, B1, and B2 were detected. A small number of individuals experienced co-infections (1.8%, 155/8,842), most commonly between RSV and influenza A/H3N2. RSV and hMPV co-infections were also found, but mainly in young children. Viral respiratory tract infection peaked locally in the rainy season (June to September). These findings support the utility of rapid nucleic acid testing of RSV, hMPV, and influenza virus in patients with ILI.

Efficacy and Safety of Danirixin (GSK1325756) Co-administered With Standard-of-Care Antiviral (Oseltamivir): A Phase 2b, Global, Randomized Study of Adults Hospitalized With Influenza

BACKGROUND

Excessive neutrophil migration has been correlated with influenza symptom severity. Danirixin (GSK1325756), a selective and reversible antagonist of C-X-C chemokine receptor 2, decreases neutrophil activation and transmigration to areas of inflammation. This study evaluated the efficacy and safety of intravenous (IV) danirixin co-administered with oseltamivir for the treatment of adults hospitalized with influenza.

METHODS

In this phase 2b, double-blind, 3-arm study (NCT02927431), influenza-positive participants were randomized 2:2:1 to receive danirixin 15mg intravenously (IV) twice daily (bid) + oral oseltamivir 75mg bid (OSV), danirixin 50mg IV bid + OSV, or placebo IV bid + OSV, for up to 5 days. The primary endpoint was time to clinical response (TTCR).

RESULTS

In total, 10 participants received study treatment (danirixin 15mg + OSV, n = 4; danirixin 50mg + OSV, n = 4; placebo + OSV, n = 2) before the study was terminated early due to low enrollment. All participants achieved a clinical response. Median (95% confidence interval) TTCR was 4.53 days (2.95, 5.71) for danirixin 15mg + OSV, 4.76 days (2.71, 5.25) for danirixin 50mg + OSV, and 1.33 days (0.71, 1.95) for placebo + OSV. Adverse events (AEs) were generally of mild or moderate intensity; no serious AEs were considered treatment-related. Interleukin-8 levels increased in nasal samples (using synthetic absorptive matrix strips) and decreased serum neutrophil-elastase-mediated degradation of elastin decreased in danirixin-treated participants, suggesting effective target engagement.

CONCLUSIONS

Interpretation of efficacy results is restricted by the low participant numbers. The safety and tolerability profile of danirixin was consistent with previous studies.

CLINICAL TRIAL INFORMATION

The registration data for the trial are in the ClinicalTrials.gov database, number NCT02927431, and in the EU Clinical Trials Register (https://www.clinicaltrialsregister.eu/) as GSK study 201023, EudraCT 2016-002512-40. Anonymized individual participant data and study documents can be requested for further research from www.clinicalstudydatarequest.com.

An international perspective on hospitalized patients with viral community-acquired pneumonia

BACKGROUND

Who should be tested for viruses in patients with community acquired pneumonia (CAP), prevalence and risk factors for viral CAP are still debated. We evaluated the frequency of viral testing, virus prevalence, risk factors and treatment coverage with oseltamivir in patients admitted for CAP.

METHODS

Secondary analysis of GLIMP, an international, multicenter, point-prevalence study of hospitalized adults with CAP. Testing frequency, prevalence of viral CAP and treatment with oseltamivir were assessed among patients who underwent a viral swab. Univariate and multivariate analysis was used to evaluate risk factors.

RESULTS

553 (14.9%) patients with CAP underwent nasal swab. Viral CAP was diagnosed in 157 (28.4%) patients. Influenza virus was isolated in 80.9% of cases. Testing frequency and viral CAP prevalence were inhomogeneous across the participating centers. Obesity (OR 1.59, 95%CI: 1.01-2.48; p = 0.043) and need for invasive mechanical ventilation (OR 1.62, 95%CI: 1.02-2.56; p = 0.040) were independently associated with viral CAP. Prevalence of empirical treatment with oseltamivir was 5.1%.

CONCLUSION

In an international scenario, testing frequency for viruses in CAP is very low. The most common cause of viral CAP is Influenza virus. Obesity and need for invasive ventilation represent independent risk factors for viral CAP. Adherence to recommendations for treatment with oseltamivir is poor.

Risk factors associated with severe outcomes in adult hospitalized patients according to influenza type and subtype

Seasonal influenza is a cause of hospitalization, especially in people with underlying disease or extreme age, and its severity may differ depending on the types and subtypes of circulating viruses. We investigated the factors associated with ICU admission or death in hospitalized patients with severe laboratory-confirmed influenza according to the viral type and subtype. An observational epidemiological study was carried out in patients aged ≥18 years from 12 Catalan hospitals between 2010 and 2016. For each reported case we collected demographic, virological and clinical characteristics. A mixed-effects logistic regression model was used to estimate crude and adjusted ORs. 1726 hospitalized patients were included: 595 (34.5%) were admitted to the ICU and 224 (13.0%) died. Lower ICU admission was associated with age ≥75 years in all influenza types and subtypes and with age 65-74 years for type A. In contrast, the 65-74 and ≥75 years age groups were associated with an increased risk of death in all types and subtypes, especially for type B (aOR 27.42, 95% CI: 4.95-151.93 and 15.96; 95% CI: 3.01-84.68). The comorbidity most closely associated with severe outcomes was immune deficiency, which was associated with death for type B (aOR 9.02, 95% CI: 3.05-26.69) and subtype A(H1N1)pdm09 (aOR 3.16, 95% CI: 1.77-5.66). Older age was a differential factor for ICU admission and death: it was associated with lower ICU admission but a risk factor for death. The comorbidity with the closest association with death was immune deficiency, mainly in influenza type B patients.

Etiology and epidemiology of community-acquired pneumonia in adults requiring hospital admission: A prospective study in rural Central Philippines

BACKGROUND

Community-acquired pneumonia (CAP) is a common cause of morbidity and mortality among adults worldwide. However, the distribution of the etiology of CAP varies from one country to another, with limited data from rural areas.

METHODS

A prospective hospital-based study on adult CAP was conducted in Leyte, Central Philippines from May 2010 to May 2012. Blood, sputum, and nasopharyngeal samples obtained from patients were used to identify pathogens using standard microbiological culture methods and PCR.

RESULTS

Of the 535 patients enrolled, 38% were younger than 50 years old. More than half of the patients had an underlying disease, including pulmonary tuberculosis (22%). The detection rate was higher for bacteria (40%) than viruses (13%). Haemophilus influenzae (12%) was the most commonly detected bacterium and influenza virus (5%) was the most commonly detected virus. The proportion of CAP patients with Mycobacterium tuberculosis infection was higher in the younger age group than in the older age group. Among CAP patients, 14% died during hospitalization, and drowsiness on admission and SpO₂ <90% were independent risk factors for mortality.

CONCLUSIONS

Bacterial infections contribute substantially to the number of hospitalizations among CAP patients in rural Philippines. This study also highlights the importance of treatment of tuberculosis in reducing the burden of adult CAP in the country.

Influenza and Viral Pneumonia

Influenza and other respiratory viruses are commonly identified in patients with community-acquired pneumonia, hospital-acquired pneumonia, and in immunocompromised patients with pneumonia. Clinically, it is difficult to differentiate viral from bacterial pneumonia. Similarly, the radiological findings of viral infection are nonspecific. The advent of polymerase chain reaction testing has enormously facilitated the identification of respiratory viruses, which has important implications for infection control measures and treatment. Currently, treatment options for patients with viral infection are limited, but there is ongoing research on the development and clinical testing of new treatment regimens and strategies.

Effective Immunization of Older Adults Against Seasonal Influenza

The 2017-2018 influenza season reminds us that it is important for health care professionals to be prepared for the annual onslaught of this contagious respiratory disease associated with potentially serious complications. Vaccination is by far the best method to prevent and control influenza, reducing illness, hospitalizations, and mortality. The highest rates of influenza-associated morbidity and mortality are observed in older adults. The immune function of older adults decreases with increasing age, a phenomenon termed immunosenescence. Immunosenescence not only confers increased susceptibility to influenza disease, but also renders vaccination less effective. To address the need for improved vaccines that provide enhanced protection to this high-risk group, 2 formulations-a high-dose vaccine and an adjuvanted vaccine-have been approved in recent years specifically for people aged 65 years and over. Here we discuss: the challenges of influenza immunization in those 65 years and older; the recent advancements in vaccines targeted at this age group; and the latest influenza vaccine recommendations for the 2017-2018 influenza season in the United States.

Multimorbidity is associated with uptake of influenza vaccination

OBJECTIVE

Patients with chronic conditions have higher rates of severe influenza-related illness and mortality. However, influenza vaccination coverage in high-risk populations continues to be suboptimal. We describe the association between cumulative disease morbidity, measured by a previously validated multimorbidity index, and influenza vaccination among community-dwelling adults.

METHODS

We obtained interview and medical record data for participants  ≥18 years who sought outpatient care for influenza-like illness between 2011 and 2016 as part of an outpatient-based study of influenza vaccine effectiveness. We defined cumulative disease morbidity by using medical diagnosis codes to calculate a multimorbidity-weighted index (MWI) for each participant. MWI and influenza vaccination status was evaluated by logistic regression. Akaike information criterion was calculated for all models.

RESULTS

Overall, 1458 (48%) of participants out of a total of 3033 received influenza vaccination. The median MWI was 0.9 (IQR 0.00-3.5) and was higher among vaccinated participants (median 1.6 versus 0.0; p < 0.001). We found a positive linear association between MWI and vaccination, and vaccination percentages were compared between categories of MWI. Compared to patients with no multimorbidity (MWI = 0), odds of vaccination were 17% higher in the second category (MWI 0.01-1.50; [OR: 1.17, 95% CI: 0.92-1.50]), 58% higher in the third category (MWI 1.51-3.00; [OR: 1.58, 95% CI: 1.26-1.99]), 130% higher in the fourth category (MWI 3.01-6.00; [OR: 2.30, 95% CI: 1.78-2.98]) and 214% higher in the fifth category (MWI 6.01-45.00;[OR: 3.14, 95% CI: 2.41-4.10]). Participants defined as high-risk had 86% greater odds of being vaccinated than non-high-risk individuals (OR: 1.86, 95% CI: 1.56-2.21). The AIC was lowest for MWI compared with high-risk conditions.

CONCLUSIONS

Our results suggest a dose response relationship between level of multimorbidity and likelihood of influenza vaccination. Compared with high-risk condition designations, MWI provided improved precision and a better model fit for the measurement of chronic disease and influenza vaccination.

Neumonías bacterianas no neumocócicas (II). Infecciones respiratorias por Mycoplasma y Chlamydia. Neumonías víricas

Las neumonías no neumocócicas y víricas se incluyen en el grupo denominado neumonías atípicas. Son causadas por un amplio grupo de bacterias y virus, no obteniéndose en la mayoría de los casos el diagnóstico etiológico. Con frecuencia su presentación suele ser leve, aunque se han descrito casos fatales, principalmente en pacientes inmunocomprometidos. En ocasiones asocian clínica extrapulmonar dificultando su diagnóstico. Las pruebas microbiológicas no están indicadas en su diagnóstico, salvo en los casos de fracaso terapéutico o ante la necesidad de hospitalización del paciente. El tratamiento antibiótico empírico precoz debe iniciarse lo antes posible, puesto que esta medida ha demostrado disminuir la morbimortalidad. Las modificaciones en el mismo o la indicación de tratamiento antivírico asociado solo se realizan según la evolución clínica o la gravedad de la presentación. Otros tratamientos como la corticoterapia continúan siendo controvertidos.

Deaths From Pneumonia-New York City, 1999-2015

Background

"Pneumonia and influenza" are the third leading cause of death in New York City. Since 2012, pneumonia and influenza have been the only infectious diseases listed among the 10 leading causes of death in NYC. Most pneumonia and influenza deaths in NYC list pneumonia as the underlying cause of death, not influenza. We therefore analyzed death certificate data for pneumonia in NYC during 1999-2015.

Methods

We calculated annualized pneumonia death rates (overall and by sociodemographic subgroup) and examined the etiologic agent listed.

Results

There were 41 400 pneumonia deaths during the study period, corresponding to an annualized age-adjusted death rate of 29.7 per 100 000 population. Approximately 17.5% of pneumonia deaths specified an etiologic agent. Age-adjusted pneumonia death rate declined over the study period and across each borough. Males had an annualized age-adjusted pneumonia death rate 1.5 (95% confidence interval [CI], 1.5-1.5) times that of females. Non-Hispanic blacks had an annualized age-adjusted pneumonia death rate 1.2 (95% CI, 1.2-1.2) times that of non-Hispanic whites. The annualized pneumonia death rate increased with age group above 5-24 years and neighborhood-level poverty. Staten Island had an annualized age-adjusted pneumonia death rate 1.3 (95% CI, 1.2-1.3) times that of Manhattan. In the multivariable analysis, pneumonia deaths were more likely to occur among males, non-Hispanic blacks, persons aged ≥65 years, residents of neighborhoods with higher poverty levels, and in Staten Island.

Conclusions

While the accuracy of death certificates is unknown, investigation is needed to understand why certain populations are disproportionately recorded as dying from pneumonia in NYC.

The impact of virus infections on pneumonia mortality is complex in adults: a prospective multicentre observational study

Background

Various viruses are known to be associated with pneumonia. However, the impact of viral infections on adult pneumonia mortality remains unclear. This study aimed to clarify the effect of virus infection on pneumonia mortality among adults stratified by virus type and patient comorbidities.

Methods

This multicentre prospective study enrolled pneumonia patients aged ≥15 years from September 2011 to August 2014. Sputum samples were tested by in-house multiplex polymerase chain reaction assays to identify 13 respiratory viruses. Viral infection status and its effect on in-hospital mortality were examined by age group and comorbidity status.

Results

A total of 2617 patients were enrolled in the study and 77.8% was aged ≥65 years. 574 (21.9%) did not have comorbidities, 790 (30.2%) had chronic respiratory disease, and 1253 (47.9%) had other comorbidities. Viruses were detected in 605 (23.1%) patients. Human rhinovirus (9.8%) was the most frequently identified virus, followed by influenza A (3.9%) and respiratory syncytial virus (3.9%). Respiratory syncytial virus was more frequently identified in patients with chronic respiratory disease (4.7%) than those with other comorbidities (4.2%) and without comorbidities (2.1%) (p = 0.037). The frequencies of other viruses were almost identical between the three groups. Virus detection overall was not associated with increased mortality (adjusted risk ratio (ARR) 0.76, 95% CI 0.53–1.09). However, influenza virus A and B were associated with three-fold higher mortality in patients with chronic respiratory disease but not with other comorbidities (ARR 3.38, 95% CI 1.54–7.42). Intriguingly, paramyxoviruses were associated with dramatically lower mortality in patients with other comorbidities (ARR 0.10, 95% CI 0.01–0.70) but not with chronic respiratory disease. These effects were not affected by age group.

Conclusions

The impact of virus infections on pneumonia mortality varies by virus type and comorbidity status in adults.

Electronic supplementary material

The online version of this article (10.1186/s12879-017-2858-y) contains supplementary material, which is available to authorized users.

Safety of Atrovent® CFC-free inhaler: respiratory events reported from an observational cohort study in England

OBJECTIVES

The aim of the study was to identify any unexpected clinical events associated with starting the new CFC-free formulation of Atrovent^® MDI in general practice in England.

METHODS

An active surveillance cohort study was conducted with a focus on selected clinical events, including respiratory symptoms, in past users of Atrovent^® CFC MDI ('switchers') and Atrovent^® naïve users. Incidence density rate ratios (with 99% confidence intervals) for events occurring in the first 3 months of exposure (risk period-ID_1-3 ) compared to 3 months prior to starting treatment (reference period-ID_R ) were calculated.

RESULTS

The cohort consisted of 13 211 patients (median age 70 years, 50.1% female; 63.5% prior users of Atrovent^® CFC MDI ('switchers')). Common respiratory events occurred at higher rates after starting treatment than before for switchers, for example lower respiratory tract infection (LRTI) [ID₁ /ID_R = 1.45 (99% CI: 1.17, 1.81)] and worsening asthma [ID₁ /ID_R = 1.58 (99% CI: 1.00, 2.51)]. Of these events only LRTI was significant for Atrovent^® naïve patients [ID₁ /ID_R = 1.42 (99% CI: 1.04, 1.95)].

CONCLUSIONS

The results of this study suggest effect modification of risk as a result of prior Atrovent^® CFC MDI use. Overall, Atrovent^® CFC-free MDI appeared to be reasonably well tolerated in the immediate postmarketing period and the safety profile appeared similar to that of the CFC formulation.

Immunogenicity and safety of an inactivated quadrivalent influenza vaccine co-administered with a 23-valent pneumococcal polysaccharide vaccine versus separate administration, in adults ≥50years of age: Results from a phase III, randomized, non-inferiority trial

INTRODUCTION

We compared co-administration versus separate administration of an inactivated quadrivalent influenza vaccine (IIV4) with a 23-valent pneumococcal polysaccharide vaccine (PPV23) in adults at high risk of complications of influenza and pneumococcal infection.

METHODS

This phase III, placebo-controlled, observer-blind trial (NCT02218697) was conducted in France and Belgium during the 2014-2015 influenza season. Adults≥50years of age meeting their country's vaccination recommendations were randomized 1:1 to co-administration or separate administration. Immunogenicity was assessed by hemagglutination inhibition (HI) titers for IIV4 and 22F-inhibition ELISA for PPV23. Co-primary objectives were to demonstrate non-inferiority of co-administration versus separate administration in terms of geometric mean titer (GMT) ratio for each influenza strain in the IIV4 and geometric mean concentration (GMC) ratio for six pneumococcal serotypes (1, 3, 4, 7F, 14, 19A) in the PPV23 in the per-protocol cohort (N=334).

RESULTS

The study met its co-primary objectives, with the upper limit of the 95% confidence interval of the GMT and GMC ratios (separate administration over co-administration) being ≤2.0 for all four antigens of the IIV4 and the six pre-selected serotypes of the PPV23, respectively. Immunogenicity of the IIV4 and PPV23 was similar regardless of administration schedule. In a post hoc analysis pooling participants ≥60years of age from the co-administration and separate administration groups, IIV4 immunogenicity was similar in higher risk adults with comorbidities (diabetes; respiratory, heart, kidney, liver, or neurological diseases; morbid obesity) versus those without. Both vaccines had an acceptable safety and reactogenicity profile; pain was the most common symptom, occurring more often with co-administration than separate administration.

CONCLUSION

The IIV4 and PPV23 can be co-administered without reducing antibody responses reflecting protection against influenza or pneumococcal disease. Co-administration of PPV23 at the annual influenza vaccination visit may improve uptake. Comorbidities had no impact on IIV4 immunogenicity, supporting its value in older adults with chronic medical conditions. Clinical Trial Registry Number: NCT02218697.

Incidence and Risk Factors of Pneumonia in Hospitalized Patients with Seasonal Influenza A or B

BACKGROUND

Most patients with influenza recover spontaneously or following treatment with an anti-viral agent, but some patients experience pneumonia requiring hospitalization. We conducted a retrospective review to determine the incidence and risk factors of pneumonia in hospitalized patients with influenza A or B.

METHODS

A total of 213 patients aged 18 years or older and hospitalized with influenza between January 2012 and January 2015 were included in this study. A reverse-transcriptase polymerase chain reaction assay was used to detect the influenza A or B virus in the patients' sputum samples. We collected demographic and laboratory data, combined coexisting diseases, and radiologic findings.

RESULTS

The incidence of pneumonia was higher in patients in the influenza A group compared to those in the influenza B group (68.6% vs. 56.9%), but this difference was not statistically significant. The presence of underlying respiratory disease was significantly associated with pneumonia in the influenza A group (adjusted odds ratio [OR], 3.975; 95% confidence interval [CI], 1.312-12.043; p=0.015). In the influenza B group, the white blood cell count (adjusted OR, 1.413; 95% CI, 1.053-1.896; p=0.021), platelet count (adjusted OR, 0.988; 95% CI, 0.978-0.999; p=0.027), and existence of an underlying medical disease (adjusted OR, 15.858; 95% CI, 1.757-143.088; p=0.014) were all significantly associated with pneumonia in multivariate analyses.

CONCLUSION

The incidence of pneumonia was 65.7% in hospitalized patients with influenza A or B. The risk factors of pneumonia differed in hospitalized patients with influenza A or B.