Intensive care unit patients with 2009 pandemic influenza A (H1N1pdm09) virus infection - United States, 2009

Eosinophils as potential biomarkers in respiratory viral infections

Eosinophils are bone marrow-derived granulocytes that, under homeostatic conditions, account for as much as 1-3% of peripheral blood leukocytes. During inflammation, eosinophils can rapidly expand and infiltrate inflamed tissues, guided by cytokines and alarmins (such as IL-33), adhesion molecules and chemokines. Eosinophils play a prominent role in allergic asthma and parasitic infections. Nonetheless, they participate in the immune response against respiratory viruses such as respiratory syncytial virus and influenza. Notably, respiratory viruses are associated with asthma exacerbation. Eosinophils release several molecules endowed with antiviral activity, including cationic proteins, RNases and reactive oxygen and nitrogen species. On the other hand, eosinophils release several cytokines involved in homeostasis maintenance and Th2-related inflammation. In the context of SARS-CoV-2 infection, emerging evidence indicates that eosinophils can represent possible blood-based biomarkers for diagnosis, prognosis, and severity prediction of disease. In particular, eosinopenia seems to be an indicator of severity among patients with COVID-19, whereas an increased eosinophil count is associated with a better prognosis, including a lower incidence of complications and mortality. In the present review, we provide an overview of the role and plasticity of eosinophils focusing on various respiratory viral infections and in the context of viral and allergic disease comorbidities. We will discuss the potential utility of eosinophils as prognostic/predictive immune biomarkers in emerging respiratory viral diseases, particularly COVID-19. Finally, we will revisit some of the relevant methods and tools that have contributed to the advances in the dissection of various eosinophil subsets in different pathological settings for future biomarker definition.

Black-White Risk Differentials in Pediatric COVID-19 Hospitalization and Intensive Care Unit Admissions in the USA

Purpose

The COVID-19 morbidity with SARS-CoV-2 as a causative pathogenic microbe remains a pandemic with children experiencing less mortality but with severe manifestations. The current study aimed to assess SARS-CoV-2 cumulative incidence, COVID-19 hospitalization, and ICU admission with respect to racial differentials.

Materials and Methods

A cross-sectional nonexperimental epidemiologic design was used to examine pediatric COVID-19 data from CDC during 2020. The variables assessed were ICU admissions, hospitalization, sex, race, and region. The Chi-Square (X²) statistic was used to examine the independence of the variables by race, while the binomial regression model was used to predict racial risk differentials in hospitalization and ICU admissions.

Results

The pediatric COVID-19 data observed the cumulative incidence of hospitalization to be 96,376, while ICU admission was 12,448. Racial differences were observed in hospitalization, ICU admissions, sex, and region. With respect to COVID-19 hospitalization, Black/African American (AA) children were two times as likely to be hospitalized compared to their White counterparts, prevalence risk ratio (pRR) = 2.20, 99% confidence interval (CI = 2.12–2.28). Similarly, Asians were 45% more likely to be hospitalized relative to their White counterparts, pRR = 1.45, 99% CI = 1.32–1.60. Regarding ICU admission, there was a disproportionate racial burden, implying excess ICU admission among Black/AA children relative to their White counterparts, pRR = 5.18, 99% CI = 4.44–6.04. Likewise, Asian children were 3 times as likely to be admitted to the ICU compared to their White counterparts, pRR = 3.36, 99% CI = 2.37–4.77. Additionally, American Indians/Alaska Natives were 2 times as likely to be admitted to ICU, pRR = 2.54, 99% CI = 0.82–7.85.

Conclusion

Racial disparities were observed in COVID-19 hospitalization and ICU admission among the US children, with Black/AA children being disproportionately affected, implying health equity transformation.

A retrospective comparison of COVID-19 and seasonal influenza mortality and outcomes in the ICUs of a French university hospital

BACKGROUND

SARS-Cov-2 (COVID-19) has become a major worldwide health concern since its appearance in China at the end of 2019.

OBJECTIVE

To evaluate the intrinsic mortality and burden of COVID-19 and seasonal influenza pneumonia in ICUs in the city of Lyon, France.

DESIGN

A retrospective study.

SETTING

Six ICUs in a single institution in Lyon, France.

PATIENTS

Consecutive patients admitted to an ICU with SARS-CoV-2 pneumonia from 27 February to 4 April 2020 (COVID-19 group) and seasonal influenza pneumonia from 1 November 2015 to 30 April 2019 (influenza group). A total of 350 patients were included in the COVID-19 group (18 refused to consent) and 325 in the influenza group (one refused to consent). Diagnosis was confirmed by RT-PCR. Follow-up was completed on 1 April 2021.

MAIN OUTCOMES AND MEASURES

Differences in 90-day adjusted-mortality between the COVID-19 and influenza groups were evaluated using a multivariable Cox proportional hazards model.

RESULTS

COVID-19 patients were younger, mostly men and had a higher median BMI, and comorbidities, including immunosuppressive condition or respiratory history were less frequent. In univariate analysis, no significant differences were observed between the two groups regarding in-ICU mortality, 30, 60 and 90-day mortality. After Cox modelling adjusted on age, sex, BMI, cancer, sepsis-related organ failure assessment (SOFA) score, simplified acute physiology score SAPS II score, chronic obstructive pulmonary disease and myocardial infarction, the probability of death associated with COVID-19 was significantly higher in comparison to seasonal influenza [hazard ratio 1.57, 95% CI (1.14 to 2.17); P = 0.006]. The clinical course and morbidity profile of both groups was markedly different; COVID-19 patients had less severe illness at admission (SAPS II score, 37 [28 to 48] vs. 48 [39 to 61], P < 0.001 and SOFA score, 4 [2 to 8] vs. 8 [5 to 11], P < 0.001), but the disease was more severe considering ICU length of stay, duration of mechanical ventilation, PEEP level and prone positioning requirement.

CONCLUSION

After ICU admission, COVID-19 was associated with an increased risk of death compared with seasonal influenza. Patient characteristics, clinical course and morbidity profile of these diseases is markedly different.

Could Interleukin-33 (IL-33) Govern the Outcome of an Equine Influenza Virus Infection? Learning from Other Species

Influenza A viruses (IAVs) are important respiratory pathogens of horses and humans. Infected individuals develop typical respiratory disorders associated with the death of airway epithelial cells (AECs) in infected areas. Virulence and risk of secondary bacterial infections vary among IAV strains. The IAV non-structural proteins, NS1, PB1-F2, and PA-X are important virulence factors controlling AEC death and host immune responses to viral and bacterial infection. Polymorphism in these proteins impacts their function. Evidence from human and mouse studies indicates that upon IAV infection, the manner of AEC death impacts disease severity. Indeed, while apoptosis is considered anti-inflammatory, necrosis is thought to cause pulmonary damage with the release of damage-associated molecular patterns (DAMPs), such as interleukin-33 (IL-33). IL-33 is a potent inflammatory mediator released by necrotic cells, playing a crucial role in anti-viral and anti-bacterial immunity. Here, we discuss studies in human and murine models which investigate how viral determinants and host immune responses control AEC death and subsequent lung IL-33 release, impacting IAV disease severity. Confirming such data in horses and improving our understanding of early immunologic responses initiated by AEC death during IAV infection will better inform the development of novel therapeutic or vaccine strategies designed to protect life-long lung health in horses and humans, following a One Health approach.

Outcomes among critically ill adults with influenza infection

Background

Influenza infection is a major cause of mortality in critical care units.

Methods

ata on critically ill adult patients with influenza infection from 2014 to 2019 were retrospectively collected, including mortality and critical care resource utilization. Independent predictors of mortality were identified using Cox regression.

Results

ne hundred thirty patients with confirmed influenza infection had a mean age of 56 (SD 16) years; 72 (55%) were male. Mean Acute Physiology and Chronic Health Evaluation (APACHE II) score was 22 (SD 9). One hundred eight (83%) patients had influenza A (46% H1N1pdm09, 33% H3N2); 21 (16%) had influenza B. Fifty-five (42%) patients had bacterial co-infection. Only 5 (4%) had fungal co-infection. One hundred eight (83%) patients required mechanical ventilation; 94 (72%), vasopressor support; 26 (20%), continuous renal replacement therapy (CRRT); and 11 (9%), extracorporeal membrane oxygenation. One hundred twenty one (93%) patients received antiviral therapy (median 5 d). Thirty-day mortality was 23%. Patients who received antiviral treatment were more likely to survive with an adjusted hazard ratio (aHR) of 0.15 (95% CI 0.04 to 0.51, p = 0.003). Other independent predictors of mortality were the need for CRRT (aHR 2.48, 95% CI 1.14 to 5.43, p = 0.023), higher APACHE II score (aHR 1.08, 95% CI 1.02 to 1.14, p = 0.011), and influenza A (aHR 7.10, 95% CI 1.37 to 36.8, p = 0.020) compared with influenza B infection.

Conclusions

mong critically ill influenza patients, antiviral therapy was independently associated with survival. CRRT, higher severity of illness, and influenza A infection were associated with mortality.

Assessment of the Association of COPD and Asthma with In-Hospital Mortality in Patients with COVID-19. A Systematic Review, Meta-Analysis, and Meta-Regression Analysis

Together, chronic obstructive pulmonary disease (COPD) and asthma account for the most common non-infectious respiratory pathologies. Conflicting preliminary studies have shown varied effect for COPD and asthma as prognostic factors for mortality in coronavirus disease 2019 (COVID-19). The aim of this study was to explore the association of COPD and asthma with in-hospital mortality in patients with COVID-19 by systematically reviewing and synthesizing with a meta-analysis the available observational studies. MEDLINE, Scopus, and medRxiv databases were reviewed. A random-effects model meta-analysis was used, and I-square was utilized to assess for heterogeneity. In-hospital mortality was defined as the primary endpoint. Sensitivity and meta-regression analyses were performed. Thirty studies with 21,309 patients were included in this meta-analysis (1465 with COPD and 633 with asthma). Hospitalized COVID-19 patients with COPD had higher risk of death compared to those without COPD (OR: 2.29; 95% CI: 1.79–2.93; I² 59.6%). No significant difference in in-hospital mortality was seen in patients with and without asthma (OR: 0.87; 95% CI: 0.68–1.10; I² 0.0%). The likelihood of death was significantly higher in patients with COPD that were hospitalized with COVID-19 compared to patients without COPD. Further studies are needed to assess whether this association is independent or not. No significant difference was demonstrated in COVID-19-related mortality between patients with and without asthma.

Clinical Characteristics and Predictors of Mortality in Critically Ill Adult Patients with Influenza Infection

Patients with influenza infection may develop acute respiratory distress syndrome (ARDS), which is associated with high mortality. Some patients with ARDS receiving extracorporeal membrane oxygenation (ECMO) support die of infectious complications. We aimed to investigate the risk factors affecting the clinical outcomes in critically ill patients with influenza. We retrospectively reviewed the medical records of influenza patients between January 2006 and May 2016 at the Kaohsiung Veterans General Hospital in Taiwan. Patients aged below 20 years or without laboratory-confirmed influenza were excluded. Critically ill patients who presented with ARDS (P = 0.004, odds ratio (OR): 8.054, 95% confidence interval (CI): 1.975–32.855), a higher Acute Physiology and Chronic Health Evaluation (APACHE) II score (P = 0.008, OR: 1.102, 95% CI: 1.025–1.184), or higher positive end-expiratory pressure (P = 0.008, OR: 1.259, 95% CI: 1.061–1.493) may have a higher risk of receiving ECMO. Influenza A (P = 0.037, OR: 0.105, 95% CI: 0.013–0.876) and multiple organ failure (P = 0.007, OR: 0.056, 95% CI: 0.007–0.457) were significantly associated with higher mortality rates. In conclusion, our study showed critically ill influenza patients with ARDS, higher APACHE II scores, and higher positive end-expiratory pressure have a higher risk of receiving ECMO support. Influenza A and multiple organ failure are predictors of mortality.

Eosinophil Responses at the Airway Epithelial Barrier during the Early Phase of Influenza A Virus Infection in C57BL/6 Mice

Eosinophils, previously considered terminally differentiated effector cells, have multifaceted functions in tissues. We previously found that allergic mice with eosinophil-rich inflammation were protected from severe influenza and discovered specialized antiviral effector functions for eosinophils including promoting cellular immunity during influenza. In this study, we hypothesized that eosinophil responses during the early phase of influenza contribute to host protection. Using in vitro and in vivo models, we found that eosinophils were rapidly and dynamically regulated upon influenza A virus (IAV) exposure to gain migratory capabilities to traffic to lymphoid organs after pulmonary infection. Eosinophils were capable of neutralizing virus upon contact and combinations of eosinophil granule proteins reduced virus infectivity through hemagglutinin inactivation. Bi-directional crosstalk between IAV-exposed epithelial cells and eosinophils occurred after IAV infection and cross-regulation promoted barrier responses to improve antiviral defenses in airway epithelial cells. Direct interactions between eosinophils and airway epithelial cells after IAV infection prevented virus-induced cytopathology in airway epithelial cells in vitro, and eosinophil recipient IAV-infected mice also maintained normal airway epithelial cell morphology. Our data suggest that eosinophils are important in the early phase of IAV infection providing immediate protection to the epithelial barrier until adaptive immune responses are deployed during influenza.

Respiratory tract infections in children with allergic asthma on allergen immunotherapy during influenza season

To describle how respiratory tract infections (RTIs) that occurred in children with allergic asthma (AA) on allergen immunotherapy (AIT) during an influenza season. Data including clinical symptoms and treatment history of children (those with AA on AIT and their siblings under 14 years old), who suffered from RTIs during an influenza season (Dec 1st, 2019–Dec 31st, 2019), were collected (by face to face interview and medical records) and analyzed. Children on AIT were divided into 2 groups: stage 1 (dose increasing stage) and stage 2 (dose maintenance stage). Their siblings were enrolled as control. During the study period, 49 children with AA on AIT (33 patients in stage 1 and 16 patients in stage 2) as well as 49 children without AA ( their siblings ) were included. There were no significant differences in occurrences of RTIs among the three groups (p > 0.05). Compared with children in the other two groups, patients with RTIs in stage 2 had less duration of coughing and needed less medicine. Children on AIT with maintenance doses had fewer symptoms and recovered quickly when they were attacked by RTIs, which suggested that AIT with dose maintenance may enhance disease resistance of the body.

Understanding building-occupant-microbiome interactions toward healthy built environments: A review

Built environments, occupants, and microbiomes constitute a system of ecosystems with extensive interactions that impact one another. Understanding the interactions between these systems is essential to develop strategies for effective management of the built environment and its inhabitants to enhance public health and well-being. Numerous studies have been conducted to characterize the microbiomes of the built environment. This review summarizes current progress in understanding the interactions between attributes of built environments and occupant behaviors that shape the structure and dynamics of indoor microbial communities. In addition, this review also discusses the challenges and future research needs in the field of microbiomes of the built environment that necessitate research beyond the basic characterization of microbiomes in order to gain an understanding of the causal mechanisms between the built environment, occupants, and microbiomes, which will provide a knowledge base for the development of transformative intervention strategies toward healthy built environments. The pressing need to control the transmission of SARS-CoV-2 in indoor environments highlights the urgency and significance of understanding the complex interactions between the built environment, occupants, and microbiomes, which is the focus of this review.

The disease burden of influenza beyond respiratory illness

Although influenza is primarily considered a respiratory infection and causes significant respiratory mortality, evidence suggests that influenza has an additional burden due to broader consequences of the illness. Some of these broader consequences include cardiovascular events, exacerbations of chronic underlying conditions, increased susceptibility to secondary bacterial infections, functional decline, and poor pregnancy outcomes, all of which may lead to an increased risk for hospitalization and death. Although it is methodologically difficult to measure these impacts, epidemiological and interventional study designs have evolved over recent decades to better take them into account. Recognizing these broader consequences of influenza virus infection is essential to determine the full burden of influenza among different subpopulations and the value of preventive approaches. In this review, we outline the main influenza complications and societal impacts beyond the classical respiratory symptoms of the disease.

Characteristics and outcomes of critically ill patients with influenza A (H1N1) in the Western Balkans during the 2019 post-pandemic season

Background

This study looked at the characteristics and outcomes of critically ill patients with confirmed influenza A (H1N1) pdm09 infection in the Western Balkans in the post-pandemic period.

Materials and Methods

This retrospective observational study of medical records and associated data collected during the post-pandemic period included all mechanically ventilated adult patients of two university-affiliated hospitals of the Western Balkans between 1 January and 31 March 2019 who had influenza A (H1N1) pdm09 infection confirmed by real-time reverse transcriptase-polymerase chain reaction from nasopharyngeal swab specimens and respiratory secretions.

Results

The study included 89 patients, 49 males (55.1%), aged 56.09 ± 12.64 years. The median time from shift from hospital time to intensive care unit was 1 day (range: 1-2). In the post-pandemic period, cases observed in this study were found to have the following comorbidities: cardiovascular diseases in 44 (49.4%) patients and diabetes in 21 (23.6%) patients. Thirty-one patients (34.8%) in this study were obese. All 89 patients (100%) experienced some degree of acute respiratory distress syndrome, and 39 (44%) had multiorgan failure. Eighty-three patients (93%) were intubated and mechanically ventilated, 6 (7%) received non-invasive mechanical ventilation, 12 (13%) were treated with vvECMO and 36 (40%) received renal replacement therapy. Vasoactive support was needed by 56 (63%) patients. The median duration of mechanical ventilation was 9 (6-15.5) days. The hospital mortality rate was 44%.

Conclusion

Critically ill patients with confirmed influenza A (H1N1) pdm09 infection in the post-pandemic season were older, required vasoactive drugs more often, and there was a trend of higher survival compared to H1N1 infection patients in the previous pandemic seasons.

Influenza A virus directly modulates mouse eosinophil responses

Allergic asthma and influenza are common respiratory diseases with a high probability of co-occurrence. During the 2009 influenza pandemic, hospitalized patients with influenza experienced lower morbidity if asthma was an underlying condition. We have previously demonstrated that acute allergic asthma protects mice from severe influenza and have implicated eosinophils in the airways of mice with allergic asthma as participants in the antiviral response. However, very little is known about how eosinophils respond to direct exposure to influenza A virus (IAV) or the microenvironment in which the viral burden is high. We hypothesized that eosinophils would dynamically respond to the presence of IAV through phenotypic, transcriptomic, and physiologic changes. Using our mouse model of acute fungal asthma and influenza, we showed that eosinophils in lymphoid tissues were responsive to IAV infection in the lungs and altered surface expression of various markers necessary for cell activation in a niche-specific manner. Siglec-F expression was altered in a subset of eosinophils after virus exposure, and those expressing high Siglec-F were more active (IL-5Rα^hi CD62L^lo ). While eosinophils exposed to IAV decreased their overall transcriptional activity and mitochondrial oxygen consumption, transcription of genes encoding viral recognition proteins, Ddx58 (RIG-I), Tlr3, and Ifih1 (MDA5), were up-regulated. CD8⁺ T cells from IAV-infected mice expanded in response to IAV PB1 peptide-pulsed eosinophils, and CpG methylation in the Tbx21 promoter was reduced in these T cells. These data offer insight into how eosinophils respond to IAV and help elucidate alternative mechanisms by which they regulate antiviral immune responses during IAV infection.

Allergic inflammation alters the lung microbiome and hinders synergistic co-infection with H1N1 influenza virus and Streptococcus pneumoniae in C57BL/6 mice

Asthma is a chronic airways condition that can be exacerbated during respiratory infections. Our previous work, together with epidemiologic findings that asthmatics were less likely to suffer from severe influenza during the 2009 pandemic, suggest that additional complications of influenza such as increased susceptibility to bacterial superinfection, may be mitigated in allergic hosts. To test this hypothesis, we developed a murine model of 'triple-disease' in which mice rendered allergic to Aspergillus fumigatus were co-infected with influenza A virus and Streptococcus pneumoniae seven days apart. Significant alterations to known synergistic effects of co-infection were noted in the allergic mice including reduced morbidity and mortality, bacterial burden, maintenance of alveolar macrophages, and reduced lung inflammation and damage. The lung microbiome of allergic mice differed from that of non-allergic mice during co-infection and antibiotic-induced perturbation to the microbiome rendered allergic animals susceptible to severe morbidity. Our data suggest that responses to co-infection in allergic hosts likely depends on the immune and microbiome states and that antibiotics should be used with caution in individuals with underlying chronic lung disease.

Spectrum of clinical and radiographic findings in patients with diagnosis of H1N1 and correlation with clinical severity

BACKGROUND

The aim of this study was to evaluate the correlation between clinical and imaging findings with a worse clinical outcome in patients with a confirmed diagnosis of H1N1 influenza A virus.

METHODS

Patients with a positive viral test for influenza A H1N1 in 2016 and chest radiography (CR) and/or computed tomography (CT) results had clinical and imaging data reviewed. Hospitalization, admission to the intensive care unit or death were defined as worse clinical outcomes. The association between clinical and imaging features and the worse outcome was calculated in a logistical regression model.

RESULTS

Eighty of 160 (50%) patients were men, with a mean age of 43 ± 19 years. The most common symptoms were as follows: flu-like symptoms 141/160 (88%), dyspnea (25/160, 17%), and thoracic pain (7/160, 5%). Abnormalities on CR were detected in 8/110 (7%) patients, and 43/59 (73%) patients had an abnormal CT. The following variables were associated with worse clinical outcomes: the presence of diabetes mellitus (DM), hypertension, dyspnea, thoracic pain, abnormal CR or CT regardless of the type of finding, CT with consolidation or ground glass opacity.

CONCLUSIONS

The presence of DM, hypertension, dyspnea, thoracic pain, or an abnormal CR or CT on admission were associated with worse clinical outcomes in patients with H1N1 influenza A virus infection. Thus, the use of readily accessible clinical and imaging features on admission may have a role in the evaluation of patients with H1N1 infection.

The Role of Innate Leukocytes during Influenza Virus Infection

Influenza virus infection is a serious threat to humans and animals, with the potential to cause severe pneumonia and death. Annual vaccination strategies are a mainstay to prevent complications related to influenza. However, protection from the emerging subtypes of influenza A viruses (IAV) even in vaccinated individuals is challenging. Innate immune cells are the first cells to respond to IAV infection in the respiratory tract. Virus replication-induced production of cytokines from airway epithelium recruits innate immune cells to the site of infection. These leukocytes, namely, neutrophils, monocytes, macrophages, dendritic cells, eosinophils, natural killer cells, innate lymphoid cells, and γδ T cells, become activated in response to IAV, to contain the virus and protect the airway epithelium while triggering the adaptive arm of the immune system. This review addresses different anti-influenza virus schemes of innate immune cells and how these cells fine-tune the balance between immunoprotection and immunopathology during IAV infection. Detailed understanding on how these innate responders execute anti-influenza activity will help to identify novel therapeutic targets to halt IAV replication and associated immunopathology.

Imaging of Emerging Infectious Diseases

Purpose of Review

Emerging infectious diseases have seen a record increase in prevalence, and understanding their management is critical in an increasingly global community. In this paper, we review current literature detailing the role of radiology in the diagnosis and treatment of the Ebola (EVD), Zika (ZVD), Chikungunya (CHIKF), H1N1, Middle East Respiratory (MERS), and Severe Acute Respiratory Syndrome (SARS) viruses.

Recent Findings

Complex protocols are required to safely use portable imaging in EVD to prevent nosocomial spread of disease. In ZVD, antenatal ultrasound can detect fetal abnormalities early, allowing implementation of care and support to affected families. Imaging is useful in assessing the extent of involvement of chronic CHIKF and monitoring treatment effect. Chest radiography and CT play a more direct role in the diagnosis and monitoring of the viral infections with primarily respiratory manifestations (H1N1, MERS, and SARS).

Summary

Radiology plays a variable role in emerging infectious diseases, requiring an understanding of disease transmission and safe imaging practices, as well as imaging features that affect clinical management.

Allergic Airway Disease Prevents Lethal Synergy of Influenza A Virus-Streptococcus pneumoniae Coinfection

Asthma has become one of the most common chronic diseases and has been identified as a risk factor for developing influenza. However, the impact of asthma on postinfluenza secondary bacterial infection is currently not known. Here, we developed a novel triple-challenge model of allergic airway disease, primary influenza infection, and secondary Streptococcus pneumoniae infection to investigate the impact of asthma on susceptibility to viral-bacterial coinfections. We report for the first time that mice recovering from acute allergic airway disease are highly resistant to influenza-pneumococcal coinfection and that this resistance is due to inhibition of influenza virus-mediated impairment of bacterial clearance. Further characterization of allergic airway disease-associated resistance against postinfluenza secondary bacterial infection may aid in the development of prophylactic and/or therapeutic treatment against coinfection.

Fatal outcomes following influenza infection are often associated with secondary bacterial infections. Allergic airway disease (AAD) is known to influence severe complications from respiratory infections, and yet the mechanistic effect of AAD on influenza virus-Streptococcus pneumoniae coinfection has not been investigated previously. We examined the impact of AAD on host susceptibility to viral-bacterial coinfections. We report that AAD improved survival during coinfection when viral-bacterial challenge occurred 1 week after AAD. Counterintuitively, mice with AAD had significantly deceased proinflammatory responses during infection. Specifically, both CD4⁺ and CD8⁺ T cell interferon gamma (IFN-γ) responses were suppressed following AAD. Resistance to coinfection was also associated with strong transforming growth factor β1 (TGF-β1) expression and increased bacterial clearance. Treatment of AAD mice with IFN-γ or genetic deletion of TGF-β receptor II expression reversed the protective effects of AAD. Using a novel triple-challenge model system, we show for the first time that AAD can provide protection against influenza virus-S. pneumoniae coinfection through the production of TGF-β that suppresses the influenza virus-induced IFN-γ response, thereby preserving antibacterial immunity.

Eosinophils and Respiratory Viruses

Eosinophils have been mainly associated with parasitic infection and pathologies such as asthma. Some patients with asthma present a high number of eosinophils in their airways. Since respiratory viruses are associated with asthma exacerbations, several studies have evaluated the role of eosinophils against respiratory viruses. Eosinophils contain and produce molecules with antiviral activity, including RNases and reactive nitrogen species. They can also participate in adaptive immunity, serving as antigen-presenting cells. Eosinophil antiviral response has been demonstrated against some respiratory viruses in vitro and in vivo, including respiratory syncytial virus and influenza. Given the implication of respiratory viruses in asthma, the eosinophil antiviral role might be an important factor to consider in this pathology.

Intranasal and epicutaneous administration of Toll-like receptor 7 (TLR7) agonists provides protection against influenza A virus-induced morbidity in mice

Toll-like receptor 7 (TLR7) is a pattern recognition receptor that recognizes viral RNA following endocytosis of the virus and initiates a powerful immune response characterized by Type I IFN production and pro-inflammatory cytokine production. Despite this immune response, the virus causes very significant pathology, which may be inflammation-dependent. In the present study, we examined the effect of intranasal delivery of the TLR7 agonist, imiquimod or its topical formulation Aldara, on the inflammation and pathogenesis caused by IAV infection. In mice, daily intranasal delivery of imiquimod prevented peak viral replication, bodyweight loss, airway and pulmonary inflammation, and lung neutrophils. Imiquimod treatment also resulted in a significant reduction in pro-inflammatory neutrophil chemotactic cytokines and prevented the increase in viral-induced lung dysfunction. Various antibody isotypes (IgG1, IgG2a, total IgG, IgE and IgM), which were increased in the BALF following influenza A virus infection, were further increased with imiquimod. While epicutaneous application of Aldara had a significant effect on body weight, it did not reduce neutrophil and eosinophil airway infiltration; indicating less effective drug delivery for this formulation. We concluded that intranasal imiquimod facilitates a more effective immune response, which can limit the pathology associated with influenza A virus infection.

Influenza in Asthmatics: For Better or for Worse?

Asthma and influenza are two pathologic conditions of the respiratory tract that affect millions worldwide. Influenza virus of the 2009 pandemic was highly transmissible and caused severe respiratory disease in young and middle-aged individuals. Asthma was discovered to be an underlying co-morbidity that led to hospitalizations during this influenza pandemic albeit with less severe outcomes. However, animal studies that investigated the relationship between allergic inflammation and pandemic (p)H1N1 infection, showed that while characteristics of allergic airways disease were exacerbated by this virus, governing immune responses that cause exacerbations may actually protect the host from severe outcomes associated with influenza. To better understand the relationship between asthma and severe influenza during the last pandemic, we conducted a systematic literature review of reports on hospitalized patients with asthma as a co-morbid condition during the pH1N1 season. Herein, we report that numerous other underlying conditions, such as cardiovascular, neurologic, and metabolic diseases may have been underplayed as major drivers of severe influenza during the 2009 pandemic. This review synopses, (1) asthma and influenza independently, (2) epidemiologic data surrounding asthma during the 2009 influenza pandemic, and (3) recent advances in our understanding of allergic host–pathogen interactions in the context of allergic airways disease and influenza in mouse models. Our goal is to showcase possible immunological benefits of allergic airways inflammation as countermeasures for influenza virus infections as a learning tool to discover novel pathways that can enhance our ability to hinder influenza virus replication and host pathology induced thereof.

Influenza infection and heart failure-vaccination may change heart failure prognosis?

The interaction of influenza infection with the pathogenesis of acute heart failure (AHF) and the worsening of chronic heart failure (CHF) is rather complex. The deleterious effects of influenza infection on AHF/CHF can be attenuated by specific immunization. Our review aimed to summarize the efficacy, effectiveness, safety, and dosage of anti-influenza vaccination in HF. In this literature review, we searched MEDLINE and EMBASE from January 1st 1966 to December 31st, 2016, for studies examining the association between AHF/CHF, influenza infections, and anti-influenza immunizations. We used broad criteria to increase the sensitivity of the search. HF was a prerequisite for our search. The search fields used included “heart failure,” “vaccination,” “influenza,” “immunization” along with variants of these terms. No restrictions on the type of study design were applied. The most common clinical scenario is exacerbation of pre-existing CHF by influenza infection. Scarce evidence supports a potential positive association of influenza infection with AHF. Vaccinated patients with pre-existing CHF have reduced all-cause morbidity and mortality, but effects are not consistently documented. Immunization with higher antigen quantity may confer additional protection, but such aggressive approach has not been generally advocated. Further studies are needed to delineate the role of influenza infection on AHF/CHF pathogenesis and maintenance. Annual anti-influenza vaccination appears to be an effective measure for secondary prevention in HF. Better immunization strategies and more efficacious vaccines are urgently necessary.

Anticoagulation increases alveolar hemorrhage in mice infected with influenza A

Influenza A virus infection is a common respiratory tract infection. Alveolar hemorrhage has been reported in patients with influenza pneumonia and in mice infected with influenza A. In this study, we investigated the effect of two anticoagulants on alveolar hemorrhage after influenza A virus (IAV) infection of wild‐type mice. Wild‐type mice were anticoagulated with either warfarin or the direct thrombin inhibitor dabigatran etexilate and then infected with a mouse‐adapted influenza virus (A/Puerto Rico/8/34 H1N1). Alveolar hemorrhage was assessed by measuring hemoglobin levels in the bronchoalveolar lavage fluid (BALF). We also measured vascular permeability and viral genomes in the lung, as well as white blood cells, inflammatory mediators, and protein in BALF. Survival and body weight were monitored for 14 days after influenza A infection. In infected mice receiving either warfarin or dabigatran etexilate we observed decreased activation of coagulation in the BALF and increased alveolar hemorrhage. Warfarin but not dabigatran etexilate increased vascular permeability and mortality of influenza A‐infected mice. Anticoagulation did not affect levels of influenza A genomes, white blood cells, inflammatory mediators, or protein in the BALF. Our study indicates that systemic anticoagulation increases alveolar hemorrhage in influenza A‐infected mice.

ICU-treated influenza A(H1N1) pdm09 infections more severe post pandemic than during 2009 pandemic: a retrospective analysis

BACKGROUND

We compared in a single mixed intensive care unit (ICU) patients with influenza A(H1N1) pdm09 between pandemic and postpandemic periods.

METHODS

Retrospective analysis of prospectively collected data in 2009-2016. Data are expressed as median (25th-75th percentile) or number (percentile).

RESULTS

Seventy-six influenza A(H1N1) pdm09 patients were admitted to the ICU: 16 during the pandemic period and 60 during the postpandemic period. Postpandemic patients were significantly older (60 years vs. 43 years, p < 0.001) and less likely to have epilepsy or other neurological diseases compared with pandemic patients (5 [8.3%] vs. 6 [38%], respectively; p = 0.009). Postpandemic patients were more likely than pandemic patients to have cardiovascular disease (24 [40%] vs. 1 [6%], respectively; p = 0.015), and they had higher scores on APACHE II (17 [13-22] vs. 14 [10-17], p = 0.002) and SAPS II (40 [31-51] vs. 31 [25-35], p = 0.002) upon admission to the ICU. Postpandemic patients had higher maximal SOFA score (9 [5-12] vs. 5 [4-9], respectively; p = 0.03) during their ICU stay. Postpandemic patients had more often septic shock (40 [66.7%] vs. 8 [50.0%], p = 0.042), and longer median hospital stays (15.0 vs. 8.0 days, respectively; p = 0.006). During 2015-2016, only 18% of the ICU- treated patients had received seasonal influenza vaccination.

CONCLUSIONS

Postpandemic ICU-treated A(H1N1) pdm09 influenza patients were older and developed more often septic shock and had longer hospital stays than influenza patients during the 2009 pandemic.

Humoral immune responses during asthma and influenza co-morbidity in mice

Humoral immunity serve dual functions of direct pathogen neutralization and enhancement of leukocyte function. Antibody classes are determined by antigen triggers, and the resulting antibodies can contribute to disease pathogenesis and host defense. Although asthma and influenza are immunologically distinct diseases, since we have found that allergic asthma exacerbation promotes antiviral host responses to influenza A virus, we hypothesized that humoral immunity may contribute to allergic host protection during influenza. C57BL/6J mice sensitized and challenged with Aspergillus fumigatus (or not) were infected with pandemic influenza A/CA/04/2009 virus. Negative control groups included naïve mice, and mice with only 'asthma' or influenza. Concentrations of antibodies were quantified by ELISA, and in situ localization of IgA- and IgE-positive cells in the lungs was determined by immunohistochemistry. The number and phenotype of B cells in spleens and mediastinal lymph nodes were determined by flow cytometry at predetermined timepoints after virus infection until viral clearance. Mucosal and systemic antibodies remained elevated in mice with asthma and influenza with prominent production of IgE and IgA compared to influenza-only controls. B cell expansion was prominent in the mediastinal lymph nodes of allergic mice during influenza where most cells produced IgG₁ and IgA. Although allergy-skewed B cell responses dominated in mice with allergic airways inflammation during influenza virus infection, virus-specific antibodies were also induced. Future studies are required to identify the mechanisms involved with B cell activation and function in allergic hosts facing respiratory viral infections.

Eosinophils Promote Antiviral Immunity in Mice Infected with Influenza A Virus

Eosinophils are multifunctional cells of the innate immune system linked to allergic inflammation. Asthmatics were more likely to be hospitalized but less likely to suffer severe morbidity and mortality during the 2009 influenza pandemic. These epidemiologic findings were recapitulated in a mouse model of fungal asthma wherein infection during heightened allergic inflammation was protective against influenza A virus (IAV) infection and disease. Our goal was to delineate a mechanism(s) by which allergic asthma may alleviate influenza disease outcome, focused on the hypothesis that pulmonary eosinophilia linked with allergic respiratory disease is able to promote antiviral host defenses against the influenza virus. The transfer of eosinophils from the lungs of allergen-sensitized and challenged mice into influenza virus-infected mice resulted in reduced morbidity and viral burden, improved lung compliance, and increased CD8+ T cell numbers in the airways. In vitro assays with primary or bone marrow-derived eosinophils were used to determine eosinophil responses to the virus using the laboratory strain (A/PR/08/1934) or the pandemic strain (A/CA/04/2009) of IAV. Eosinophils were susceptible to IAV infection and responded by activation, piecemeal degranulation, and upregulation of Ag presentation markers. Virus- or viral peptide-exposed eosinophils induced CD8+ T cell proliferation, activation, and effector functions. Our data suggest that eosinophils promote host cellular immunity to reduce influenza virus replication in lungs, thereby providing a novel mechanism by which hosts with allergic asthma may be protected from influenza morbidity.

"Obesity Paradox" in Acute Respiratory Distress Syndrome: Asystematic Review and Meta-Analysis

Background

It is unclear whether an “obesity paradox” exists in the respiratory system, especially in acute respiratory distress syndrome (ARDS) and acute lung injury (ALI). Previous studies have postulated a causal relation between obesity and ARDS/ALI but have lacked power to form a definitive conclusion.

Objective

To investigate the relationships between obesity, ARDS/ALIrisk, and mortality.

Methods

A systematic search current to April 2016 was performed in Pubmed, EMBASE, Medline, Cochrane databases to find relevant studies. All studies that estimate the effect of obesity in the morbidity and mortality of ARDS/ALI were included.

Results

A total of 24 studies including 9,187,248 subjects were analyzed. The combined results from 16 studies that examined the effect of obesity in morbidity of ARDS/ALI showed an89% increase in odds ratio(pooled odds ratios (OR) 1.89, 95% confidence intervals (CI) 1.45 to 2.47). In subgroup analysis, compared to normal weight, obesity was associated with an increased risk of ARDS/ALI (OR1.57, 95% CI 1.30–1.90 for obese (BMI30-39.9kg/m²); OR1.75, 95% CI 1.42–2.15 for obese(BMI≥30kg/m²); OR1.67, 95% CI 1.04–2.68 for morbid obese(BMI≥40kg/m²)). The combined results from 9 studies that examined the effect of obesity in mortality of ARDS/ALI had a pooled odds ratio(pooled OR 0.63, 95% CI 0.41 to 0.98). Inversely, obesity was significantly associated with reduced risk of ARDS/ALI mortality(OR0.88, 95% CI 0.78–1.00 for overweight(BMI≤18.5m²); OR0.74, 95% CI 0.64–0.84 for obese (BMI30-39.9kg/m²);OR0.84, 95% CI 0.75–0.94 for 60days mortality; OR0.38, 95% CI 0.22–0.66 for 90days mortality).

Conclusions

Our data identify obesity as an important risk factor for the development of ARDS/ALI; however, ARDS/ALI outcomes are improved in this population when compared to individuals with a normal body mass index. This meta-analysis results supported ‘‘obesity paradox” in ARDS/ALI.

Successful management of H1N1 related severe acute respiratory distress syndrome with noninvasive positive pressure ventilation

Acute respiratory distress syndrome (ARDS) is a life threatening complication of H1N1 pneumonia. According to the Berlin conference guidelines, severe ARDS requires management with early invasive mechanical ventilation. Whether noninvasive positive pressure ventilation (NIPPV) should be attempted in patients with H1N1 pneumonia is still a matter of debate. We report the case of one patient with severe ARDS without other organ failure. The patient was managed successfully using NIPPV. Endotracheal intubation was avoided and the patient was discharged from the intensive care unit (ICU) after 10 days with a successful outcome. NIPPV can be useful in patients with isolated severe H1N1 ARDS provided early improvement of the oxygenation parameters is achieved. Patients with multiple organ failure or with persistent severe hypoxemia under noninvasive ventilation should be electively intubated and started on invasive mechanical ventilation.

The role of viral infections in exacerbations of chronic obstructive pulmonary disease and asthma

Asthma and chronic obstructive pulmonary disease (COPD) are major causes of global morbidity and mortality worldwide. The clinical course of both asthma and COPD are punctuated by the occurrence of exacerbations, acute events characterized by increased symptoms and airflow obstruction. Exacerbations contribute most of the morbidity, mortality and excess healthcare costs associated with both asthma and COPD. COPD and asthma exacerbations are frequently associated with respiratory virus infections and this has led to an intense research focus into the mechanisms of virus-induced exacerbations over the past decade. Current therapies are effective in reducing chronic symptoms but are less effective in preventing exacerbations, particularly in COPD. Understanding the mechanisms of virus-induced exacerbation will lead to the development of new targeted therapies that can reduce the burden of virus-induced exacerbations. In this review we discuss current knowledge of virus-induced exacerbations of asthma and COPD with a particular focus on mechanisms, human studies, virus-bacteria interactions and therapeutic advances.

Burden and viral aetiology of influenza-like illness and acute respiratory infection in intensive care units

The purpose of this investigation was to study the viral aetiology of influenza-like illness (ILI) and acute respiratory tract infection (ARTI) among patients requiring intensive care unit admission. A cross-sectional retrospective study was carried out in Sicily over a 4-year period. A total of 233 respiratory samples of patients with ILI/ARTI admitted to intensive care units were molecularly analyzed for the detection of a comprehensive panel of aetiologic agents of viral respiratory infections. About 45% of patients was positive for at least one pathogen. Single aetiology occurred in 75.2% of infected patients, while polymicrobial infection was found in 24.8% of positive subjects. Influenza was the most common aetiologic agent (55.7%), especially among adults. Most of patients with multiple aetiology (76.9%) were adults and elderly. Mortality rates among patients with negative or positive aetiology did not significantly differ (52.4% and 47.6%, respectively). Highly transmissible respiratory pathogens are frequently detected among patients with ILI/ARTI admitted in intensive care units, showing the occurrence of concurrent infections by different viruses. The knowledge of the circulation of several types of microorganisms is of crucial importance in terms of appropriateness of therapies, but also for the implication in prevention strategies and hospital epidemiology.

The PAndemic INfluenza Triage in the Emergency Department (PAINTED) pilot cohort study

BACKGROUND

Research needs to be undertaken rapidly in the event of an influenza pandemic to develop and evaluate triage methods for people presenting to the emergency department with suspected pandemic influenza.

OBJECTIVES

We aimed to pilot a research study to be undertaken in a pandemic to identify the most accurate triage method for patients presenting to the emergency department with suspected pandemic influenza. The objectives of the pilot study were to develop a standardised clinical assessment form and secure online database; test both using data from patients with seasonal influenza; seek clinician views on the usability of the form; and obtain all regulatory approvals required for the main study.

DESIGN

Study methods were piloted using an observational cohort study and clinician views were sought using qualitative, semistructured interviews.

SETTING

Six acute hospital emergency departments.

PARTICIPANTS

Patients attending the emergency department with suspected seasonal influenza during winter 2012-13 and clinicians working in the emergency departments.

MAIN OUTCOME MEASURES

Adverse events up to 30 days were identified, but analysis of the pilot data was limited to descriptive reporting of patient flow, data completeness and patient characteristics.

RESULTS

Some 165 patients were identified, of whom 10 withdrew their data, leaving 155 (94%) for analysis. Follow-up data were available for 129 of 155 (83%), with 50 of 129 (39%) being admitted to hospital. Three cases (2%) were recorded as having suffered an adverse outcome. There appeared to be variation between the hospitals, allowing for small numbers. Three of the hospitals identified 150 of 165 (91%) of the patients, and all 10 withdrawing patients were at the same hospital. The proportion with missing follow-up data varied from 8% to 31%, and the proportion admitted varied from 4% to 85% across the three hospitals with meaningful numbers of cases. All of the deaths were at one hospital. There was less variation between hospitals in rates of missing data, and for most key variables missing rates were between 5% and 30%. Higher missing rates were recorded for blood pressure (39%), inspired oxygen (43%), capillary refill (36%) and Glasgow Coma Scale score (43%). Chest radiography was performed in 51 of 118 cases, and electrocardiography in 40 of 111 cases with details recorded. Blood test results were available for 32 of 155 cases. The qualitative interviews revealed generally positive views towards the standardised assessment form. Concerns about lack of space for free text were raised but counterbalanced by appreciation that it fitted on to one A4 page. A number of amendments were suggested but only three of these were suggested by more than one participant, and no suggestions were made by more than two participants.

CONCLUSIONS

A standardised assessment form is acceptable to clinicians and could be used to collect research data in an influenza pandemic, but analysis may be limited by missing data.

FUTURE WORK

An observational cohort study to identify the most accurate triage method for predicting severe illness in emergency department attendees with suspected pandemic influenza is set up and ready to activate if, or when, a pandemic occurs.

TRIAL REGISTRATION

Current Controlled Trials ISRCTN56149622.

FUNDING

This project was funded by the NIHR Health Technology Assessment programme and will be published in full in Health Technology Assessment; Vol. 19, No. 3. See the NIHR Journals Library website for further project information.

Epidemiological features of influenza in Canadian adult intensive care unit patients

To identify predictive factors and mortality of patients with influenza admitted to intensive care units (ICU) we carried out a prospective cohort study of patients hospitalized with laboratory-confirmed influenza in adult ICUs in a network of Canadian hospitals between 2006 and 2012. There were 626 influenza-positive patients admitted to ICUs over the six influenza seasons, representing 17·9% of hospitalized influenza patients, 3·1/10,000 hospital admissions. Variability occurred in admission rate and proportion of hospital influenza patients who were admitted to ICUs (proportion range by year: 11·7-29·4%; 21·3% in the 2009-2010 pandemic). In logistic regression models ICU patients were younger during the pandemic and post-pandemic period, and more likely to be obese than hospital non-ICU patients. Influenza B accounted for 14·2% of all ICU cases and had a similar ICU admission rate as influenza A. Influenza-related mortality was 17·8% in ICU patients compared to 2·0% in non-ICU patients.

Severe Influenza in 33 US Hospitals, 2013–2014: Complications and Risk Factors for Death in 507 Patients

BACKGROUND

Influenza A (H1N1) pdm09 became the predominant circulating strain in the United States during the 2013–2014 influenza season. Little is known about the epidemiology of severe influenza during this season.

METHODS

A retrospective cohort study of severely ill patients with influenza infection in intensive care units in 33 US hospitals from September 1, 2013, through April 1, 2014, was conducted to determine risk factors for mortality present on intensive care unit admission and to describe patient characteristics, spectrum of disease, management, and outcomes.

RESULTS

A total of 444 adults and 63 children were admitted to an intensive care unit in a study hospital; 93 adults (20.9%) and 4 children (6.3%) died. By logistic regression analysis, the following factors were significantly associated with mortality among adult patients: older age (>65 years, odds ratio, 3.1 [95% CI, 1.4–6.9], P=.006 and 50–64 years, 2.5 [1.3–4.9], P=.007; reference age 18–49 years), male sex (1.9 [1.1–3.3], P=.031), history of malignant tumor with chemotherapy administered within the prior 6 months (12.1 [3.9–37.0], P<.001), and a higher Sequential Organ Failure Assessment score (for each increase by 1 in score, 1.3 [1.2–1.4], P<.001).

CONCLUSION

Risk factors for death among US patients with severe influenza during the 2013–2014 season, when influenza A (H1N1) pdm09 was the predominant circulating strain type, shifted in the first postpandemic season in which it predominated toward those of a more typical epidemic influenza season.

Infect. Control Hosp. Epidemiol. 2015;36(11):1251–1260

Description of hospitalized cases of influenza A(H1N1)pdm09 infection on the basis of the national hospitalized-case surveillance, 2009-2010, Japan

This study reports the epidemiological characteristics of hospitalized cases of influenza A(H1N1)pdm09 infection analyzed on the basis of surveillance data collected from July 24, 2009, the date on which the hospital-based surveillance of influenza cases was implemented in Japan, to September 5, 2010. During the study period, 13,581 confirmed cases were reported. Among those cases with information regarding the reason for hospitalization, 39% were admitted to hospitals for non-therapeutic purposes such as medical observation and laboratory testing. The overall hospitalization rate was 5.8 cases per 100,000 population when cases hospitalized for non-therapeutic purposes were excluded. While those aged under 20 years accounted for over 85% of hospitalized cases, the largest proportion of fatal cases was observed in those aged over 65 years. The overall case fatality rate for all hospitalized cases was 1.5%. The year-round surveillance for hospitalized influenza-like illness cases was launched in 2011, and it was expected that this surveillance system could add value by monitoring changes in the epidemiological characteristics of hospitalized cases of seasonal influenza.

Preventing ARDS: progress, promise, and pitfalls

Advances in critical care practice have led to a substantial decline in the incidence of ARDS over the past several years. Low tidal volume ventilation, timely resuscitation and antimicrobial administration, restrictive transfusion practices, and primary prevention of aspiration and nosocomial pneumonia have likely contributed to this reduction. Despite decades of research, there is no proven pharmacologic treatment of ARDS, and mortality from ARDS remains high. Consequently, recent initiatives have broadened the scope of lung injury research to include targeted prevention of ARDS. Prediction scores have been developed to identify patients at risk for ARDS, and clinical trials testing aspirin and inhaled budesonide/formoterol for ARDS prevention are ongoing. Future trials aimed at preventing ARDS face several key challenges. ARDS has not been validated as an end point for pivotal clinical trials, and caution is needed when testing toxic therapies that may prevent ARDS yet potentially increase mortality.

Global burden of influenza as a cause of cardiopulmonary morbidity and mortality

Severe acute respiratory infections, including influenza, are a leading cause of cardiopulmonary morbidity and mortality worldwide. Until recently, the epidemiology of influenza was limited to resource-rich countries. Emerging epidemiological reports characterizing the 2009 H1N1 pandemic, however, suggest that influenza exerts an even greater toll in low-income, resource-constrained environments where it is the cause of 5% to 27% of all severe acute respiratory infections. The increased burden of disease in this setting is multifactorial and likely is the result of higher rates of comorbidities such as human immunodeficiency virus, decreased access to health care, including vaccinations and antiviral medications, and limited healthcare infrastructure, including oxygen therapy or critical care support. Improved global epidemiology of influenza is desperately needed to guide allocation of life-saving resources, including vaccines, antiviral medications, and direct the improvement of basic health care to mitigate the impact of influenza infection on the most vulnerable populations.

Chest Radiological Findings of Patients With Severe H1N1 Pneumonia Requiring Intensive Care

INTRODUCTION

A new strain of human influenza A (H1N1) virus originated from Mexico in 2009 and spread to more than 190 countries and territories. The World Health Organization (WHO) declared it a level 6 (highest level) pandemic. In August 2010, WHO announced that the H1N1 2009 influenza virus had moved into the postpandemic period. The WHO also declared that this flu strain is expected to continue to circulate as a seasonal virus "for some years to come." The objective of this study is to describe the chest radiographic and computed tomography (CT) findings of patients with severe H1N1 pneumonia admitted to the intensive care unit (ICU) during the 2009 pandemic.

HYPOTHESIS

Patients with severe H1N1 pneumonia requiring ICU admission have extensive radiographic and CT abnormalities.

METHODS

Eighteen patients, aged 23 to 62 (mean 41), admitted to the ICU at UCLA-Olive View Medical Center with a primary diagnosis of pandemic H1N1 infection, confirmed either via rapid influenza detection test or by real-time reverse transcriptase polymerase chain reaction assay, formed the study population. All patients had chest x-ray (CXR) within 24 hours of admission and 5 patients had CT examinations. In this retrospective study, images were evaluated for the pattern (ground-glass opacities, consolidation, reticular opacities, and nodular opacities), distribution (unilateral/bilateral, upper/middle/lower lung zone, and central/peripheral/peribronchovascular), and extent (focal/multifocal/diffuse; number of lung zones) of abnormalities.

RESULTS

All (100%) patients had abnormal CXR and CT studies. The predominant radiographic findings were ground-glass opacities (16 of 18; 89%), consolidation (16 of 18; 89%), and reticular opacities (6 of 18, 33%). The radiographic abnormalities were bilateral in 17 (94%) patients; involved lower lung distribution in 18 (100%) patients, and mid and lower lung distribution in 16 (89%) patients. Radiographic abnormalities were peribronchovascular in 11 (61%) patients and multifocal in 10 (56%). Sixteen (89%) patients had extensive abnormalities involving 3 or more lung zones. The patients requiring mechanical ventilation had a higher incidence of bilateral, diffuse consolidation in a peribronchovascular distribution on chest radiographs. The predominant CT abnormalities were consolidation (5 of 5; 100%), ground-glass opacities (5 of 5; 100%), and nodular opacities (3 of 5, 60%). The CT findings were peribronchovascular and multifocal in 4 (80%) patients and extensive and bilateral in all (100%) patients.

CONCLUSIONS

Patients with H1N1 pneumonia admitted to the ICU had bilateral, extensive CXR, and CT abnormalities. Consolidations and ground-glass opacities were the most common imaging findings, predominantly affecting mid and lower lung zones. Imaging abnormalities were peribronchovascular and multifocal in a majority of patients.

Interim estimates of 2013/14 influenza clinical severity and vaccine effectiveness in the prevention of laboratory-confirmed influenza-related hospitalisation, Canada, February 2014

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A conceptual approach to improving care in pandemics and beyond: severe lung injury centers

The events of the 2009 influenza pandemic sparked discussion regarding the need to optimize delivery of care to those most severely ill. We propose in this conceptual study that a tiered regionalization care system be instituted for patients with severe acute respiratory distress syndrome. Such system would be a component of national pandemic plans and could also be used in day-to-day operations.