Predominant role of bacterial pneumonia as a cause of death in pandemic influenza: implications for pandemic influenza preparedness

The 1918 influenza pandemic hastened the decline of tuberculosis in the United States: an age, period, cohort analysis

The effect of the 1918 influenza pandemic on other diseases is a neglected topic in historical epidemiology. This paper takes up the hypothesis that the influenza pandemic affected the long-term decline of tuberculosis through selective mortality, such that many people with tuberculosis were killed in 1918, depressing subsequent tuberculosis mortality and transmission. Regularly collected vital statistics data on mortality of influenza and tuberculosis in the US are presented and analyzed demographically. The available population-level data fail to contradict the selection hypothesis. More work is needed to understand fully the role of multiple morbidities in the 1918 influenza pandemic.

Successive influenza virus infection and Streptococcus pneumoniae stimulation alter human dendritic cell function

BACKGROUND

Influenza virus is a major cause of respiratory disease worldwide and Streptococcus pneumoniae infection associated with influenza often leads to severe complications. Dendritic cells are key antigen presenting cells but its role in such co-infection is unclear.

METHODS

In this study, human monocyte derived-dentritic cells were either concurrently or successively challenged with the combination of live influenza virus and heat killed pneumococcus to mimic the viral pneumococcal infection. Dendritic cell viability, phenotypic maturation and cytokine production were then examined.

RESULTS

The challenge of influenza virus and pneumococcus altered dendritic cell functions dependent on the time interval between the successive challenge of influenza virus and pneumococcus, as well as the doses of pneumococcus. When dendritic cells were exposed to pneumococcus at 6 hr, but not 0 hr nor 24 hr after influenza virus infection, both virus and pneumococcus treated dendritic cells had greater cell apoptosis and expressed higher CD83 and CD86 than dendritic cells infected with influenza virus alone. Dendritic cells produced pro-inflammatory cytokines: TNF-α, IL-12 and IFN-γ synergistically to the successive viral and pneumococcal challenge. Whereas prior influenza virus infection suppressed the IL-10 response independent of the timing of the subsequent pneumococcal stimulation.

CONCLUSIONS

Our results demonstrated that successive challenge of dendritic cells with influenza virus and pneumococcus resulted in synergistic up-regulation of pro-inflammatory cytokines with simultaneous down-regulation of anti-inflammatory cytokine, which may explain the immuno-pathogenesis of this important co-infection.

The possible roles of solar ultraviolet-B radiation and vitamin D in reducing case-fatality rates from the 1918-1919 influenza pandemic in the United States

Deaths during the 1918-1919 influenza pandemic have been linked to both the influenza virus and secondary bacterial lung infections. Case fatality rates and percentage of influenza cases complicated by pneumonia were available from survey data for twelve United States locations in the 1918-1919 pandemic. This study analyzes case fatality rates and cases complicated by pneumonia with respect to estimated summertime and wintertime solar ultraviolet-B (UVB) doses as indicators of population mean vitamin D status. Substantial correlations were found for associations of July UVB dose with case fatality rates (r = -0.72, p = 0.009) and rates of pneumonia as a complication of influenza (r = -0.77, p = 0.005). Similar results were found for wintertime UVB. Vitamin D upregulates production of human cathelicidin, LL-37, which has both antimicrobial and antiendotoxin activities. Vitamin D also reduces the production of proinflammatory cytokines, which could also explain some of the benefit of vitamin D since H1N1 infection gives rise to a cytokine storm. The potential role of vitamin D status in reducing secondary bacterial infections and loss of life in pandemic influence requires further evaluation.

Swine flu: lessons we need to learn from our global experience

There are important lessons to be learnt from the recent 'Swine Flu' pandemic. Before we call it a pandemic, we need to have appropriate trigger points that involve not only the spread of the virus but also its level of virulence. This was not done for H1N1 (swine flu). We need to ensure that we improve the techniques used in trying to decrease the spread of infection-both in the community and within our hospitals. This means improved infection control and hygiene, and the use of masks, alcohol hand rubs and so on. We also need to have a different approach to vaccines. Effective vaccines were produced only after the epidemic had passed and therefore had relatively little impact in preventing many infections. Mass population strategies involving vaccines and antivirals also misused large amounts of scarce medical resources.

Association of bacterial pneumonia and respiratory failure in children with community-acquired influenza infection

OBJECTIVE

To investigate the association of bacterial pneumonia and respiratory failure in children with community-acquired influenza infection presenting to a pediatric intensive care unit.

DESIGN

Retrospective cohort study.

SETTING

Pediatric intensive care unit at an urban academic tertiary-care children's hospital.

PATIENTS

All patients aged <18 yrs admitted to our pediatric intensive care unit with laboratory-confirmed influenza infection between October 2002 and September 2008.

INTERVENTIONS

All patients who met our clinical definitions of respiratory failure and bacterial pneumonia were identified. Patients were stratified by presence or absence of chronic medical conditions associated with an increased risk of influenza-related complications.

MEASUREMENTS AND MAIN RESULTS

There were 59 patients admitted to the pediatric intensive care unit with laboratory-confirmed community-acquired influenza during the period of study. Twenty-four patients (41%) had respiratory failure and 14 patients (24%) met the definition of bacterial pneumonia. The risk of respiratory failure was increased in the presence of bacterial pneumonia (p = .04). Adjusting for age and chronic medical conditions, patients with bacterial pneumonia had a 3.7 times greater odds (p = .04) of respiratory failure.

CONCLUSIONS

Our findings suggest that bacterial pneumonia was associated with increased odds of respiratory failure in both previously healthy children and those with chronic medical conditions. Early aggressive therapy should be considered for patients with severe influenza.

Toll-Like Receptors Dysregulation after Influenza Virus Infection: Insights into Pathogenesis of Subsequent Bacterial Pneumonia

The innate immune system utilizes an intricate network to aid in fighting foreign invaders. Recent insight and understanding of toll-like receptors (TLRs) has been critical in providing key information about early responses to infection, and more recently, understanding dysregulation of TLRs has shed light on pathogenic states. This paper addresses the importance of innate immunity and TLR regulation of immune responses to the presence of influenza infection and its role in the subsequent bacterial infections.

Contribution of cytokines to pathology and protection in virus infection

Acute and chronic viral infections greatly contribute to global health burden. While concerted action of multiple elements of the immune system help the host cope with most viruses, some infections lead to host damage or death. Cytokines are central drivers and controllers of both immune-mediated virus elimination and of immunopathology. Here, we review recent progress in understanding the protective and damaging roles in viral infections of cytokines and chemokines associated with innate, regulatory, and Th1, Th2 and Th17 responses.

Family and community concerns about post-mortem needle biopsies in a Muslim society

Background

Post-mortem needle biopsies have been used in resource-poor settings to determine cause of death and there is interest in using them in Bangladesh. However, we did not know how families and communities would perceive this procedure or how they would decide whether or not to consent to a post-mortem needle biopsy. The goal of this study was to better understand family and community concerns and decision-making about post-mortem needle biopsies in this low-income, predominantly Muslim country in order to design an informed consent process.

Methods

We conducted 16 group discussions with family members of persons who died during an outbreak of Nipah virus illness during 2004-2008 and 11 key informant interviews with their community and religious leaders. Qualitative researchers first described the post-mortem needle biopsy procedure and asked participants whether they would have agreed to this procedure during the outbreak. Researchers probed participants about the circumstances under which the procedure would be acceptable, if any, their concerns about the procedure, and how they would decide whether or not to consent to the procedure.

Results

Overall, most participants agreed that post-mortem needle biopsies would be acceptable in some situations, particularly if they benefitted society. This procedure was deemed more acceptable than full autopsy because it would not require major delays in burial or remove organs, and did not require cutting or stitching of the body. It could be performed before the ritual bathing of the body in either the community or hospital setting. However, before consent would be granted for such a procedure, the research team must gain the trust of the family and community which could be difficult. Although consent may only be provided by the guardians of the body, decisions about consent for the procedure would involve extended family and community and religious leaders.

Conclusions

The possible acceptability of this procedure during outbreaks represents an important opportunity to better characterize cause of death in Bangladesh which could lead to improved public health interventions to prevent these deaths. Obstacles for research teams will include engaging all major stakeholders in decision-making and quickly building a trusting relationship with the family and community, which will be difficult given the short window of time prior to the ritual bathing of the body.

Successful use of venovenous extracorporeal membrane oxygenation for complicated H1N1 pneumonia refractory to mechanical ventilation

In April 2009, novel H1N1 influenza A pneumonia was initially identified in young adults by the Mexican Health Ministry. Previously healthy patients progressing to multisystem organ failure were common. Worldwide, hospitals reported surges in intensive care admissions during the initial phase of the pandemic. In patients with H1N1 pneumonia refractory to mechanical ventilation, centers were initially reporting low survival rates despite the use of extracorporeal membrane oxygenation (ECMO). The initial poor outcomes and protracted ECMO treatment epochs resulted in centers limiting or withholding the use of ECMO in this population. With respect to children with H1N1 infection there was uncertainty concerning optimal incorporation of ECMO as a therapeutic option. In children with rapidly progressive pneumonia and hypoxia refractory to mechanical ventilation, venovenous (VV) ECMO has been successfully used with survival ranging from 40-60% depending on the etiology. We report the successful use of VV ECMO in two children with confirmed novel H1N1 complicated by bacterial pneumonia or morbid obesity. Our Institutional Review Board waived the need for consent. Prompt initiation of VV ECMO resulted in rapid clinical improvement, radiographic resolution of diffuse consolidation, and return of full neurocognitive function. For children with rapidly progressive respiratory distress on conventional ventilation, VV ECMO can be used to improve outcomes when initiated early in the disease process even in children with a significant co-morbidity.

Temporal association between rhinovirus circulation in the community and invasive pneumococcal disease in children

BACKGROUND

Mucosal coinfections with respiratory viruses and Streptococcus pneumoniae are common, but the role of rhinovirus infections in the development of invasive pneumococcal disease (IPD) in children has not been studied.

METHODS

During 1995 and 2007, we analyzed the association of IPD in children less than 5 years of age with respiratory virus epidemics by combining data from the National Infectious Disease Register, 3 prospective epidemiologic studies, and the database of the Department of Virology, University of Turku, Finland.

RESULTS

The mean IPD rate in children younger than 5 years of age in Finland was 2.9 cases per week (95% confidence interval [CI], 2.5-3.3) during periods of high rhinovirus activity, and 1.4 (95% CI, 1.2-1.6) during periods of low rhinovirus activity (P < 0.001). The IPD rate correlated with the rhinovirus activity recorded at the Department of Virology (correlation coefficient, 0.23; P = 0.001) and in the epidemiologic studies (correlation coefficients, 0.28, 0.25, and 0.31). The IPD rate was moderately increased during periods of high respiratory syncytial virus activity (mean, 2.1 cases per week; 95% CI, 1.8-2.3) compared with periods of low respiratory syncytial virus activity (mean, 1.7; 95% CI, 1.6-1.9; P = 0.008). There were no differences in the IPD rate between the periods of high and low influenza activity.

CONCLUSIONS

Rhinovirus circulation in the community had an association with IPD in children younger than 5 years of age. This study suggests that rhinovirus infection may be a contributor in the development of IPD in the population of young children.

Airway immune homeostasis and implications for influenza-induced inflammation

The lung is exposed to a myriad of innocuous antigens on a daily basis and must maintain a state of immune ignorance or tolerance to these harmless stimuli to retain pulmonary homeostasis and to prevent potentially fatal immunopathology. Here, we examine how, in the lower airways, resident cell populations contribute to the immune regulatory strategies that restrain inflammation. During influenza infection, these suppressive signals must be overcome to elicit a protective immune response that eliminates the virus. We also discuss how, after resolution of infection, the lung does not return to the original homeostatic state, and how the induced altered state can persist for long periods, which leaves the lung more susceptible to other infectious insults.

FluCAN 2009: initial results from sentinel surveillance for adult influenza and pneumonia in eight Australian hospitals

OBJECTIVE

To describe the epidemiology of adult patients hospitalised with influenza or pneumonia during a pandemic season in a sentinel network in Australia.

DESIGN, PARTICIPANTS AND SETTING

Prospective case series of adult hospital admissions to eight acute care general public hospitals (Influenza Complications Alert Network [Flu CAN] sentinel hospitals) in six Australian jurisdictions, 1 July to 4 December 2009.

MAIN OUTCOME MEASURES

Demographic, clinical and outcome measures in patients admitted with laboratory-confirmed pandemic (H1N1) 2009 influenza in the sentinel hospitals compared with data from national notifications and intensive care unit (ICU) surveillance; admissions for influenza and pneumonia over time in each jurisdiction.

RESULTS

During 190 hospital-weeks of observation, there were 538 influenza admissions. Of these, 465 patients (86.4%) had the pandemic strain, representing 9.3% of total admissions with pandemic (H1N1) 2009 influenza (n = 4992) recorded nationally in 2009. Of these patients, 250/465 (53.8%) were women, 67/453 (14.8%) were Indigenous, and the median age was 46 years (interquartile range, 29-58 years). Comorbidities were present in 354/464 patients (76.3%), and 40 were pregnant (30.3% of women aged 15-49 years). FluCAN reported that 102 patients (21.9%) were admitted to ICUs, and of patients admitted to hospital, 26 (5.6%) died. FluCAN results were very similar to national notification data and published ICU admissions data. Of those who were followed to 30 days after discharge, 30 (6.5%) were readmitted. Of 1468 patients hospitalised with pneumonia, 718 (48.9%) were tested for influenza and 163 (11.1%) were co-infected with the pandemic strain.

CONCLUSIONS

Sentinel surveillance systems can provide important and reliable information in a timely fashion and can monitor changes in severity of influenza during a pandemic season.

Inactivated and live, attenuated influenza vaccines protect mice against influenza: Streptococcus pyogenes super-infections

Mortality associated with influenza virus super-infections is frequently due to secondary bacterial complications. To date, super-infections with Streptococcus pyogenes have been studied less extensively than those associated with Streptococcus pneumoniae. This is significant because a vaccine for S. pyogenes is not clinically available, leaving vaccination against influenza virus as our only means for preventing these super-infections. In this study, we directly compared immunity induced by two types of influenza vaccine, either inactivated influenza virus (IIV) or live, attenuated influenza virus (LAIV), for the ability to prevent super-infections. Our data demonstrate that both IIV and LAIV vaccines induce similar levels of serum antibodies, and that LAIV alone induces IgA expression at mucosal surfaces. Upon super-infection, both vaccines have the ability to limit the induction of pro-inflammatory cytokines within the lung, including IFN-γ which has been shown to contribute to mortality in previous models of super-infection. Limiting expression of these pro-inflammatory cytokines within the lungs subsequently limits recruitment of macrophages and neutrophils to pulmonary surfaces, and ultimately protects both IIV- and LAIV-vaccinated mice from mortality. Despite their overall survival, both IIV- and LAIV-vaccinated mice demonstrated levels of bacteria within the lung tissue that are similar to those seen in unvaccinated mice. Thus, influenza virus:bacteria super-infections can be limited by vaccine-induced immunity against influenza virus, but the ability to prevent morbidity is not complete.

Pre-admission statin use and in-hospital severity of 2009 pandemic influenza A(H1N1) disease

BACKGROUND

Statins are drugs that are used to lower plasma cholesterol levels. Recently, contradictory claims have been made about possible additional effects of statins on progression of a variety of inflammatory disorders, including infections. We therefore examined the clinical course of patients admitted to hospital with 2009 pandemic influenza A(H1N1), who were or weren't taking statins at time of admission.

METHODS

A retrospective case-control study was performed using the United Kingdom Influenza Clinical Information Network (FLU-CIN) database, containing detailed information on 1,520 patients admitted to participating hospitals with confirmed 2009 pandemic influenza A(H1N1) infection between April 2009 and January 2010. We confined our analysis to those aged over 34 years. Univariate analysis was used to calculate unadjusted odds ratios (OR) and 95 percent confidence intervals (95%CI) for factors affecting progression to severe outcome (high dependency or intensive care unit level support) or death (cases); two multivariable logistic regression models were then established for age and sex, and for age, sex, obesity and "indication for statin" (e.g., heart disease or hypercholesterolaemia).

RESULTS

We found no statistically significant association between pre-admission statin use and severity of outcome after adjustment for age and sex [adjusted OR: 0.81 (95% CI: 0.46-1.38); n = 571]. After adjustment for age, sex, obesity and indication for statin, the association between pre-admission statin use and severe outcome was not statistically significant; point estimates are compatible with a small but clinically significant protective effect of statin use [adjusted OR: 0.72 (95% CI: 0.38-1.33)].

CONCLUSIONS

In this group of patients hospitalized with pandemic influenza, a significant beneficial effect of pre-admission statin use on the in-hospital course of illness was not identified. Although the database from which these observations are derived represents the largest available suitable UK hospital cohort, a larger study would be needed to confirm whether there is any benefit in this setting.

Increased mortality of solid organ transplant recipients with H1N1 infection: a single center experience

Immunosuppressed solid organ transplant recipients are included in the cohort at increased risk for complications of viral infections such as the newly encountered H1N1. A retrospective review was performed to collect data on patients hospitalized during a recent H1N1 epidemic. H1N1 was suspected based on symptoms and real-time reverse-transcriptase-polymerase-chain-reaction assay confirmed the diagnosis. From August through October of 2009, 89 patients were admitted to The Methodist Hospital, Houston, Texas, with H1N1. Eighteen were solid organ transplant recipients with an age range of 34-69 yr. This group included nine kidney, five lung, one kidney-pancreas, one liver, and two heart recipients. Severe cardiac or pulmonary comorbidities existed in over half of non-transplant patients, while only eight of these non-transplant patients were otherwise healthy. Eighty-nine percent of transplant patients presented with fever or chills, 72% with cough, and 56% with gastrointestinal distress. Symptoms were similar to non-transplant patients. All transplant patients were treated with oseltamivir. Two non-transplant patients and three transplant patients died. Thirty-day survival was 97% in non-transplant and 83% in transplant patients (p=0.02). In the context of an initial epidemic of H1N1, infection was associated with increased risk of complications and mortality in solid organ transplant recipients.

The ability of pandemic influenza virus hemagglutinins to induce lower respiratory pathology is associated with decreased surfactant protein D binding

Pandemic influenza viral infections have been associated with viral pneumonia. Chimeric influenza viruses with the hemagglutinin segment of the 1918, 1957, 1968, or 2009 pandemic influenza viruses in the context of a seasonal H1N1 influenza genome were constructed to analyze the role of hemagglutinin (HA) in pathogenesis and cell tropism in a mouse model. We also explored whether there was an association between the ability of lung surfactant protein D (SP-D) to bind to the HA and the ability of the corresponding chimeric virus to infect bronchiolar and alveolar epithelial cells of the lower respiratory tract. Viruses expressing the hemagglutinin of pandemic viruses were associated with significant pathology in the lower respiratory tract, including acute inflammation, and showed low binding activity for SP-D. In contrast, the virus expressing the HA of a seasonal influenza strain induced only mild disease with little lung pathology in infected mice and exhibited strong in vitro binding to SP-D.

Viral pneumonia

About 200 million cases of viral community-acquired pneumonia occur every year-100 million in children and 100 million in adults. Molecular diagnostic tests have greatly increased our understanding of the role of viruses in pneumonia, and findings indicate that the incidence of viral pneumonia has been underestimated. In children, respiratory syncytial virus, rhinovirus, human metapneumovirus, human bocavirus, and parainfluenza viruses are the agents identified most frequently in both developed and developing countries. Dual viral infections are common, and a third of children have evidence of viral-bacterial co-infection. In adults, viruses are the putative causative agents in a third of cases of community-acquired pneumonia, in particular influenza viruses, rhinoviruses, and coronaviruses. Bacteria continue to have a predominant role in adults with pneumonia. Presence of viral epidemics in the community, patient's age, speed of onset of illness, symptoms, biomarkers, radiographic changes, and response to treatment can help differentiate viral from bacterial pneumonia. However, no clinical algorithm exists that will distinguish clearly the cause of pneumonia. No clear consensus has been reached about whether patients with obvious viral community-acquired pneumonia need to be treated with antibiotics. Apart from neuraminidase inhibitors for pneumonia caused by influenza viruses, there is no clear role for use of specific antivirals to treat viral community-acquired pneumonia. Influenza vaccines are the only available specific preventive measures. Further studies are needed to better understand the cause and pathogenesis of community-acquired pneumonia. Furthermore, regional differences in cause of pneumonia should be investigated, in particular to obtain more data from developing countries.

The influenza pandemic of 2009: lessons and implications

Influenza is a moving target, which evolves in unexpected directions and is recurrent annually. The 2009 influenza A/H1N1 pandemic virus was unlike the 2009 seasonal virus strains and originated in pigs prior to infecting humans. Three strains of viruses gave rise to the pandemic virus by antigenic shift, reassortment, and recombination, which occurred in pigs as 'mixing vessels'. The three strains of viruses had originally been derived from birds, pigs, and humans. The influenza hemagglutinin (HA) and neuraminidase (NA) external proteins are used to categorize and group influenza viruses. The internal proteins (PB1, PB1-F2, PB2, PA, NP, M, and NS) are involved in the pathogenesis of influenza infection. A major difference between the 1918 and 2009 pandemic viruses is the lack of the pathogenic protein PB1-F2 in the 2009 pandemic strains, which was present in the more virulent 1918 pandemic strains. We provide an overview of influenza infection since 1847 and the advent of influenza vaccination since 1944. Vaccines and chemotherapy help reduce the spread of influenza, reduce morbidity and mortality, and are utilized by the global rapid-response organizations associated with the WHO. Immediate identification of impending epidemic and pandemic strains, as well as sustained vigilance and collaboration, demonstrate continued success in combating influenza.

Role of procalcitonin and C-reactive protein in differentiation of mixed bacterial infection from 2009 H1N1 viral pneumonia

Please cite this paper as: Ahn et al. (2011) Role of procalcitonin and C‐reactive protein in differentiation of mixed bacterial infection from 2009 H1N1 viral pneumonia. Influenza and Other Respiratory Viruses 5(6), 398–403.

Background  Mixed bacterial infection is an important contributor to morbidity and mortality during influenza pandemics. We evaluated procalcitonin (PCT) and C‐reactive protein (CRP) in differentiating pneumonia caused by mixed bacterial and 2009 H1N1 influenza infection from 2009 H1N1 influenza infection alone.

Methods  Data were collected retrospectively over a 7‐month period during the 2009 H1N1 influenza pandemic. Patients visiting emergency department and diagnosed as community‐acquired pneumonia caused by 2009 H1N1 infection were included (n = 60).

Results  Mixed bacterial and viral infection pneumonia (n = 16) had significantly higher PCT and CRP levels than pneumonia caused by 2009 H1N1 influenza alone (n = 44, P = 0·019, 0·022 respectively). The sensitivity and specificity for detection of mixed bacterial infection pneumonia was 56% and 84% for PCT > 1·5 ng/ml, and 69% and 63% for CRP > 10 mg/dl. Using PCT and CRP in combination, the sensitivity and specificity were 50% and 93%, respectively.

Conclusion  Procalcitonin and CRP alone and their combination had a moderate ability to detect pneumonia of mixed bacterial infection during the 2009 H1N1 pandemic. Considering high specificity, combination of low CRP and PCT result may suggest that pneumonia is unlikely to be caused by mixed bacterial infection.

Molecular imaging of influenza and other emerging respiratory viral infections

Research on the pathogenesis and therapy of influenza and other emerging respiratory viral infections would be aided by methods that directly visualize pathophysiologic processes in patients and laboratory animals. At present, imaging of diseases, such as swine-origin H1N1 influenza, is largely restricted to chest radiograph and computed tomography (CT), which can detect pulmonary structural changes in severely ill patients but are more limited in characterizing the early stages of illness, differentiating inflammation from infection or tracking immune responses. In contrast, imaging modalities, such as positron emission tomography, single photon emission CT, magnetic resonance imaging, and bioluminescence imaging, which have become useful tools for investigating the pathogenesis of a range of disease processes, could be used to advance in vivo studies of respiratory viral infections in patients and animals. Molecular techniques might also be used to identify novel biomarkers of disease progression and to evaluate new therapies.

Co-detection of pandemic (H1N1) 2009 virus and other respiratory pathogens

From May through October 2009, a total of 10,624 clinical samples from 23 US states were screened for multiple respiratory pathogen gene targets. Of 3,110 (29.3%) samples positive for pandemic (H1N1) 2009 virus, 28% contained ≥ 1 other pathogen, most commonly Staphylococcus aureus (14.7%), Streptococcus pneumoniae (10.2%), and Haemophilus influenzae (3.5%).

Immunotherapy with a combination of intravenous immune globulin and p4 peptide rescues mice from postinfluenza pneumococcal pneumonia

Alternate therapies are needed for treatment of secondary bacterial pneumonia following influenza. The immunomodulatory peptide P4 has shown promise in mouse models of primary pneumococcal infection. Mice infected with influenza virus and then challenged with Streptococcus pneumoniae were treated with a combination of P4 peptide and intravenous immune globulin. Survival was improved from 20% to 80% in treated mice relative to controls. Clinical cure correlated with increased clearance of bacteria and decreased lung consolidation. Greater trafficking of professional phagocytic cells to the site of pneumococcal infection coupled with enhanced opsonophagocytosis as manifest by decreased surface display of Fcγ receptors (FcγR) on neutrophils and macrophages were associated with P4 peptide treatment. This suggests that the mechanism of action for improved clearance of bacteria engendered by P4 is through improved uptake by phagocytes mediated by IgG Fc-Fcγ receptor interactions following antibody-mediated opsonophagocytosis of bacteria. Antibody-based therapies, when coupled with immune modulators, such as P4 peptide, may be an effective tool together with antibiotics in our armamentarium against severe pneumonia.

Computer-aided diagnosis of pulmonary infections using texture analysis and support vector machine classification

RATIONALE AND OBJECTIVES

The purpose of this study was to develop and test a computer-assisted detection method for the identification and measurement of pulmonary abnormalities on chest computed tomographic (CT) imaging in cases of infection, such as novel H1N1 influenza. The method developed could be a potentially useful tool for classifying and quantifying pulmonary infectious disease on CT imaging.

MATERIALS AND METHODS

Forty chest CT examinations were studied using texture analysis and support vector machine classification to differentiate normal from abnormal lung regions on CT imaging, including 10 patients with immunohistochemistry-proven infection, 10 normal controls, and 20 patients with fibrosis.

RESULTS

Statistically significant differences in the receiver-operating characteristic curves for detecting abnormal regions in H1N1 infection were obtained between normal lung and regions of fibrosis, with significant differences in texture features of different infections. These differences enabled the quantification of abnormal lung volumes on CT imaging.

CONCLUSION

Texture analysis and support vector machine classification can distinguish between areas of abnormality in acute infection and areas of chronic fibrosis, differentiate lesions having consolidative and ground-glass appearances, and quantify those texture features to increase the precision of CT scoring as a potential tool for measuring disease progression and severity.

Hospitalized children with 2009 influenza a (H1N1) infection in Shenzhen, China, November-December 2009

OBJECTIVES

During the winter outbreak of 2009 influenza A (H1N1) infection in China, the number of confirmed cases and the fatal cases has grown rapidly. We describe the clinical characteristics of hospitalized children with 2009 influenza A (H1N1) infection in Shenzhen, China, November-December 2009.

METHODS

Using a standardized form, we collected data on 148 hospitalized children. 2009 influenza A (H1N1) infection was confirmed in nasopharyngeal swab specimens with the use of a real-time reverse transcriptase-polymerase chain reaction assay.

RESULTS

Of the 148 hospitalized children with 2009 influenza A (H1N1) infection, 81 (55%) were 5 years of age or older and 85% of the patients were previously healthy. The common presenting symptoms were fever (94%), cough (89%), runny nose (36.5%), vomiting (24%), sore throat (19.6%), wheezing (18%), abdominal pain (16%), mental status changes (9%), seizures (6%), diarrhea (6%), myalgia (6%), and chest pain (4%). Twenty-nine (20%) patients were admitted to an ICU, 10 (7%) patients required mechanical ventilation. The overall complication rate was 65.5%, they were pneumonia in 94 (64%), neurologic complications in 18 (12%), parapneumonic effusion in 12 (8%) and myocarditis in 7 (5%). One hundred seven (72%) patients received oseltamivir treatment, 34 (23%) received within 48 hr after the onset of symptoms. All patients received antibiotics before admission or on admission. One hundred forty-four (97%) patients were discharged; four (3%) previously healthy patients died, three died from severe encephalopathy, one died from secondary fungal meningitis.

CONCLUSION

Hospitalized children with 2009 influenza A (H1N1) infection can have a wide range of presentation and clinical complications including neurologic complications. The severe cases and deaths concentrate in previously healthy older children.

Clinical and laboratory features distinguishing pandemic H1N1 influenza-related pneumonia from interpandemic community-acquired pneumonia in adults

BACKGROUND

Early identification of patients with H1N1 influenza-related pneumonia is desirable for the early instigation of antiviral agents. A study was undertaken to investigate whether adults admitted to hospital with H1N1 influenza-related pneumonia could be distinguished clinically from patients with non-H1N1 community-acquired pneumonia (CAP).

METHODS

Between May 2009 and January 2010, clinical and epidemiological data of patients with confirmed H1N1 influenza infection admitted to 75 hospitals in the UK were collected by the Influenza Clinical Information Network (FLU-CIN). Adults with H1N1 influenza-related pneumonia were identified and compared with a prospective study cohort of adults with CAP hospitalised between September 2008 and June 2010, excluding those admitted during the period of the pandemic.

RESULTS

Of 1046 adults with confirmed H1N1 influenza infection in the FLU-CIN cohort, 254 (25%) had H1N1 influenza-related pneumonia on admission to hospital. In-hospital mortality of these patients was 11.4% compared with 14.0% in patients with inter-pandemic CAP (n=648). A multivariate logistic regression model was generated by assigning one point for each of five clinical criteria: age ≤ 65 years, mental orientation, temperature ≥ 38 °C, leucocyte count ≤ 12 × 10(9)/l and bilateral radiographic consolidation. A score of 4 or 5 predicted H1N1 influenza-related pneumonia with a positive likelihood ratio of 9.0. A score of 0 or 1 had a positive likelihood ratio of 75.7 for excluding it.

CONCLUSION

There are substantial clinical differences between H1N1 influenza-related pneumonia and inter-pandemic CAP. A model based on five simple clinical criteria enables the early identification of adults admitted with H1N1 influenza-related pneumonia.

A review of mathematical models of influenza A infections within a host or cell culture: lessons learned and challenges ahead

Most mathematical models used to study the dynamics of influenza A have thus far focused on the between-host population level, with the aim to inform public health decisions regarding issues such as drug and social distancing intervention strategies, antiviral stockpiling or vaccine distribution. Here, we investigate mathematical modeling of influenza infection spread at a different scale; namely that occurring within an individual host or a cell culture. We review the models that have been developed in the last decades and discuss their contributions to our understanding of the dynamics of influenza infections. We review kinetic parameters (e.g., viral clearance rate, lifespan of infected cells) and values obtained through fitting mathematical models, and contrast them with values obtained directly from experiments. We explore the symbiotic role of mathematical models and experimental assays in improving our quantitative understanding of influenza infection dynamics. We also discuss the challenges in developing better, more comprehensive models for the course of influenza infections within a host or cell culture. Finally, we explain the contributions of such modeling efforts to important public health issues, and suggest future modeling studies that can help to address additional questions relevant to public health.

Pneumonia in patients with novel influenza A (H1N1) virus in Southeastern Turkey

The objective of this study was to describe the clinical characteristics and the radiological and laboratory findings of the hospitalised patients who had novel, laboratory-confirmed, swine-origin influenza A virus (S-OIV) infection with pneumonia. Between October and December 2009, 56 patients hospitalised for pneumonia who were tested for S-OIV infection were retrospectively evaluated. Thirty-three patients had positive S-OIV infections. In addition, 23 of the 56 patients who had negative test results for S-OIV infection were compared with the positive group. The mortality rate amongst the patients with S-OIV infection was 24.2%. Of the 33 patients, 42.4% had at least one underlying medical condition and 4 (12%) patients were pregnant or postpartum. Fourteen patients (42.4%) with S-OIV infection were followed up in an intensive care unit. The most common symptom was dyspnea. The mean peak body temperature during hospital stay (39.42 ± 0.70) was higher in this group than in the negative group (38.51 ± 1.05) (p = 0.001). Thrombocytopenia, increased creatine kinase and elevated lactate dehydrogenase levels were statistically significant. Bilateral infiltration was more common in the patients with S-OIV infection. Although some laboratory, radiological and clinical data show a significant difference between the patients with S-OIV pneumonia and the negative group, each patient presenting with signs of pneumonia during pandemia should be tested for Influenza A.

Isolation of Aspergillus in three 2009 H1N1 influenza patients

Please cite this paper as: Adalja et al. (2011) Isolation of Aspergillus in three 2009 H1N1 influenza patients. Influenza and Other Respiratory Viruses 5(4), 225–229

Objectives:  To describe the association of Aspergillus with influenza.

Design/Setting/Sample  Three case reports of ICU patients with influenza complicated by the isolation of Aspergillus species are described and a review of the literature on the topic was performed.

Conclusions:  Severe influenza cases can be complicated by Aspergillus infection.

Severe pandemic 2009 H1N1 influenza disease due to pathogenic immune complexes

Pandemic influenza viruses often cause severe disease in middle-aged adults without preexisting comorbidities. The mechanism of illness associated with severe disease in this age group is not well understood. Here we find preexisting serum antibodies that cross-react with, but do not protect against, 2009 H1N1 influenza virus in middle-aged adults. Nonprotective antibody is associated with immune complex-mediated disease after infection. We detected high titers of serum antibody of low avidity for H1-2009 antigen, and low-avidity pulmonary immune complexes against the same protein, in severely ill individuals. Moreover, C4d deposition--a marker of complement activation mediated by immune complexes--was present in lung sections of fatal cases. Archived lung sections from middle-aged adults with confirmed fatal influenza 1957 H2N2 infection revealed a similar mechanism of illness. These observations provide a previously unknown biological mechanism for the unusual age distribution of severe cases during influenza pandemics.

Effect of 1918 PB1-F2 expression on influenza A virus infection kinetics

Relatively little is known about the viral factors contributing to the lethality of the 1918 pandemic, although its unparalleled virulence was likely due in part to the newly discovered PB1-F2 protein. This protein, while unnecessary for replication, increases apoptosis in monocytes, alters viral polymerase activity in vitro, enhances inflammation and increases secondary pneumonia in vivo. However, the effects the PB1-F2 protein have in vivo remain unclear. To address the mechanisms involved, we intranasally infected groups of mice with either influenza A virus PR8 or a genetically engineered virus that expresses the 1918 PB1-F2 protein on a PR8 background, PR8-PB1-F2(1918). Mice inoculated with PR8 had viral concentrations peaking at 72 hours, while those infected with PR8-PB1-F2(1918) reached peak concentrations earlier, 48 hours. Mice given PR8-PB1-F2(1918) also showed a faster decline in viral loads. We fit a mathematical model to these data to estimate parameter values. The model supports a higher viral production rate per cell and a higher infected cell death rate with the PR8-PB1-F2(1918) virus. We discuss the implications these mechanisms have during an infection with a virus expressing a virulent PB1-F2 on the possibility of a pandemic and on the importance of antiviral treatments.

Multidrug-resistant 2009 pandemic influenza A(H1N1) viruses maintain fitness and transmissibility in ferrets

BACKGROUND

The 2009 influenza A(H1N1) pandemic called attention to the limited influenza treatment options available, especially in individuals at high risk of severe disease. Neuraminidase inhibitor-resistant seasonal H1N1 viruses have demonstrated the ability to transmit well despite early data indicating that resistance reduces viral fitness. 2009 H1N1 pandemic viruses have sporadically appeared containing resistance to neuraminidase inhibitors and the adamantanes, but the ability of these viruses to replicate, transmit, and cause disease in mammalian hosts has not been fully characterized.

METHODS

Two pretreatment wild-type viruses and 2 posttreatment multidrug-resistant viruses containing the neuraminidase H275Y mutation collected from immunocompromised patients infected with pandemic influenza H1N1 were tested for viral fitness, pathogenicity, and transmissibility in ferrets.

RESULTS

The pretreatment wild-type viruses and posttreatment resistant viruses containing the H275Y mutation all demonstrated significant pathogenicity and equivalent viral fitness and transmissibility.

CONCLUSIONS

The admantane-resistant 2009 pandemic influenza A(H1N1) virus can develop the H275Y change in the neuraminidase gene conferring resistance to both oseltamivir and peramivir without any loss in fitness, transmissibility, or pathogenicity. This suggests that the dissemination of widespread multidrug resistance similar to neuraminidase inhibitor resistance in seasonal H1N1 is a significant threat.

Influenza virus primes mice for pneumonia from Staphylococcus aureus

Superinfections from Staphylococcus aureus following influenza are an increasing concern. We assessed several laboratory and clinical strains in a mouse coinfection model with influenza virus. A methicillin-resistant USA300 clone and several recent clinical strains from patients with necrotizing pneumonia caused high mortality following influenza virus infection in mice. Both viral and bacterial lung titers were enhanced during coinfections compared with single infections. However, differences in titers did not correspond with differences in disease outcomes in a comparison of superinfections from a highly pathogenic strain with those from a poorly pathogenic strain. These strains did differ, however, in expression of Panton-Valentine leukocidin and in the degree of inflammatory lung damage each engendered. The viral cytotoxin PB1-F2 contributed to the negative outcomes. These data suggest that additional study of specific bacterial virulence factors involved in the pathogenesis of inflammation and lung damage during coinfections is needed.

Overview/reflections on the 2009 H1N1 pandemic

The Influenza A H1N1 2009 pandemic was a test of the global public health response. Strategies that worked included mass vaccine production and antivirals while quarantine and isolation proved futile. Among the lessons learned was the importance of severity in the definition of a pandemic.

Glucose depletion in the airway surface liquid is essential for sterility of the airways

Diabetes mellitus predisposes the host to bacterial infections. Moreover, hyperglycemia has been shown to be an independent risk factor for respiratory infections. The luminal surface of airway epithelia is covered by a thin layer of airway surface liquid (ASL) and is normally sterile despite constant exposure to bacteria. The balance between bacterial growth and killing in the airway determines the outcome of exposure to inhaled or aspirated bacteria: infection or sterility. We hypothesized that restriction of carbon sources--including glucose--in the ASL is required for sterility of the lungs. We found that airway epithelia deplete glucose from the ASL via a novel mechanism involving polarized expression of GLUT-1 and GLUT-10, intracellular glucose phosphorylation, and low relative paracellular glucose permeability in well-differentiated cultures of human airway epithelia and in segments of airway epithelia excised from human tracheas. Moreover, we found that increased glucose concentration in the ASL augments growth of P. aeruginosa in vitro and in the lungs of hyperglycemic ob/ob and db/db mice in vivo. In contrast, hyperglycemia had no effect on intrapulmonary bacterial growth of a P. aeruginosa mutant that is unable to utilize glucose as a carbon source. Our data suggest that depletion of glucose in the airway epithelial surface is a novel mechanism for innate immunity. This mechanism is important for sterility of the airways and has implications in hyperglycemia and conditions that result in disruption of the epithelial barrier in the lung.

Intranasal vaccination with pneumococcal surface protein A plus poly(I:C) protects against secondary pneumococcal pneumonia in mice

Effective pneumococcal vaccines are required for preventing secondary bacterial pneumonia, a life-threatening condition, during epidemics of influenza. We examined whether nasal administration of a low dose of pneumococcal surface protein A (PspA) plus polyinosinic-polycytidylic acid (poly(I:C)) could protect against a fatal secondary pneumococcal pneumonia after influenza A virus infection in mice. PspA-specific IgG but not IgA level was higher in the airways and blood of mice nasally administered a low dose of PspA plus poly(I:C) than in mice nasally administered PspA alone or poly(I:C) alone. Binding of PspA-specific IgG increased C3 deposition on the bacterial surface. The survival rate during secondary infection was higher in mice immunized with PspA plus poly(I:C) than in mice immunized with poly(I:C) alone. The significant reduction in bacterial density in the lung and blood was associated with increased survival of immunized mice with secondary pneumonia. Passive transfer of sera from mice immunized with PspA plus poly(I:C) increased the survival of mice infected with secondary pneumonia. Our data suggest that an intranasal PspA vaccine has promising protective effects against secondary pneumonia after influenza and that PspA-specific IgG plays a critical role in this protection.

Are there any differences in clinical and laboratory findings on admission between H1N1 positive and negative patients with flu-like symptoms?

Background

The World Health Organization alert for the H1N1 influenza pandemic led to the implementation of certain measures regarding admission of patients with flu-like symptoms. All these instructions were adopted by the Greek National Health System. The aim of this study was to retrospectively examine the characteristics of all subjects admitted to the Unit of Infectious Diseases with symptoms indicating H1N1 infection, and to identify any differences between H1N1 positive or negative patients. Patients from the ED (emergency department) with flu-like symptoms (sore throat, cough, rhinorhea, or nasal congestion) and fever >37.5°C were admitted in the Unit of Infectious diseases and gave pharyngeal or nasopharyngeal swabs. Swabs were tested with real-time reverse-transcriptase-polymerase-chain-reaction (RT-PCR).

Findings

Patients were divided into two groups. Group A comprised 33 H1N1 positive patients and Group B (control group) comprised of 27 H1N1 negative patients. The two groups did not differ in terms of patient age, co-morbidities, length of hospitalization, temperature elevation, hypoxemia, as well as renal and liver function. There were also no significant differences in severity on admission. C-reactive protein (CRP) (mean 12.8 vs. 5.74) and white blood count (WBC) (mean 10.528 vs. 7.114) were significantly higher in group B than in group A upon admission. Obesity was noted in 8 patients of Group A (mean 31.67) and 14 patients of Group B (mean 37.78). Body mass index (BMI) was lower in H1N1 positive than in H1N1 negative patients (mean 31.67 vs. 37.78, respectively; p = 0.009).

Conclusions

The majority of patients in both groups were young male adults. CRP, WBC and BMI were higher among H1N1 negative patients. Finally, clinical course of patients in both groups was mild and uneventful.

Promoting life course vaccination

Infectious diseases remain a significant cause of morbi-mortality in adults aged over 60 years, and many of these diseases are vaccine-preventable (VPDs). There is a pressing need to promote a lifelong vaccine schedule to increase vaccination against VPDs during the different stages of life. We outline the impact of vaccines on the burden of common infectious diseases and consider the negative clinical impact of VPDs in the unvaccinated population. We further illustrate that vaccine uptake is associated with a reduction in the burden of VPDs at any age of life, due to herd immunity. Disability-free and healthy aging is closely linked to childhood health and medical conditions in young adulthood. The midlife vaccine gap drastically impacts health in later life, especially in unvaccinated and older populations. These arguments underline the need for a preventive lifelong health perspective from childhood through old age.

Virulence determinants of pandemic influenza viruses

Influenza A viruses cause recurrent, seasonal epidemics and occasional global pandemics with devastating levels of morbidity and mortality. The ability of influenza A viruses to adapt to various hosts and undergo reassortment events ensures constant generation of new strains with unpredictable degrees of pathogenicity, transmissibility, and pandemic potential. Currently, the combination of factors that drives the emergence of pandemic influenza is unclear, making it impossible to foresee the details of a future outbreak. Identification and characterization of influenza A virus virulence determinants may provide insight into genotypic signatures of pathogenicity as well as a more thorough understanding of the factors that give rise to pandemics.

Influenza pandemics

The recent H1N1 pandemic that emerged in 2009 has illustrated how swiftly a new influenza virus can circulate the globe. Here we explain the origins of the 2009 pandemic virus, and other twentieth century pandemics. We also consider the impact of the 2009 pandemic in the human population and the use of vaccines and antiviral drugs. Thankfully this outbreak was much less severe than that associated with Spanish flu in 1918. We describe the viral factors that affect virulence of influenza and speculate on the future course of this virus in humans and animals.

Preventing and treating secondary bacterial infections with antiviral agents

Bacterial super-infections contribute to the significant morbidity and mortality associated with influenza and other respiratory virus infections. There are robust animal model data, but only limited clinical information on the effectiveness of licensed antiviral agents for the treatment of bacterial complications of influenza. The association of secondary bacterial pathogens with fatal pneumonia during the recent H1N1 influenza pandemic highlights the need for new development in this area. Basic and clinical research into viral-bacterial interactions over the past decade has revealed several mechanisms that underlie this synergism. By applying these insights to antiviral drug development, the potential exists to improve outcomes by means other than direct inhibition of the virus.

The airway epithelium: soldier in the fight against respiratory viruses

The airway epithelium acts as a frontline defense against respiratory viruses, not only as a physical barrier and through the mucociliary apparatus but also through its immunological functions. It initiates multiple innate and adaptive immune mechanisms which are crucial for efficient antiviral responses. The interaction between respiratory viruses and airway epithelial cells results in production of antiviral substances, including type I and III interferons, lactoferrin, β-defensins, and nitric oxide, and also in production of cytokines and chemokines, which recruit inflammatory cells and influence adaptive immunity. These defense mechanisms usually result in rapid virus clearance. However, respiratory viruses elaborate strategies to evade antiviral mechanisms and immune responses. They may disrupt epithelial integrity through cytotoxic effects, increasing paracellular permeability and damaging epithelial repair mechanisms. In addition, they can interfere with immune responses by blocking interferon pathways and by subverting protective inflammatory responses toward detrimental ones. Finally, by inducing overt mucus secretion and mucostasis and by paving the way for bacterial infections, they favor lung damage and further impair host antiviral mechanisms.