pH1N1 Influenza Research Articles

Molecular Evolutionary Analysis of pH1N1 2009 Influenza Virus in Reunion Island, South West Indian Ocean Region: A Cohort Study

Background/ObjectivesMolecular epidemiology is a powerful tool to decipher the dynamics of viral transmission, quasispecies temporal evolution and origins. Little is known about the pH1N1 molecular dynamics in general population. A prospective study (CoPanFlu-RUN) was carried out in Reunion Island to characterize pH1N1 genetic variability and molecular evolution occurring in population during the pH1N1 Influenza pandemic in 2009.MethodologyWe directly amplified pH1N1 genomes from 28 different nasal swabs (26 individuals from 21 households). Fifteen strains were fully sequenced and 13 partially. This includes pairs of sequences from different members of 5 separate households; and two pairs from individuals, collected at different times. We assessed the molecular evolution of pH1N1 by genetic variability and phylogenetic analyses.Principal FindingsWe found that i) Reunion pH1N1 sequences stemmed from global “clade 7” but shaped two phylogenetic sub-clades; ii) D239E mutation was identified in the hemagglutinin protein of all Reunion sequences, a mutation which has been associated elsewhere with mild-, upper-respiratory tract pH1N1 infecting strains; iii) Date estimates from molecular phylogenies predicted clade emergence some time before the first detection of pH1N1 by the epidemiological surveillance system; iv) Phylogenetic relatedness was observed between Reunion pH1N1 viruses and those from other countries in South-western Indian Ocean area; v) Quasispecies populations were observed within households and individuals of the cohort-study.ConclusionsSurveillance and/or prevention systems presently based on Influenza virus sequence variation should take into account that the majority of studies of pH1N1 Influenza generate genetic data for the HA/NA viral segments obtained from hospitalized-patients, which is potentially non-representative of the overall viral diversity within whole populations. Our observations highlight the importance of collecting unbiased data at the community level and conducting whole genome analysis to accurately understand viral dynamics.

A method for analyzing clustered interval‐censored data based on Cox's model

Methods for analyzing interval-censored data are well established. Unfortunately, these methods are inappropriate for the studies with correlated data. In this paper, we focus on developing a method for analyzing clustered interval-censored data. Our method is based on Cox's proportional hazard model with piecewise-constant baseline hazard function. The correlation structure of the data can be modeled by using Clayton's copula or independence model with proper adjustment in the covariance estimation. We establish estimating equations for the regression parameters and baseline hazards (and a parameter in copula) simultaneously. Simulation results confirm that the point estimators follow a multivariate normal distribution, and our proposed variance estimations are reliable. In particular, we found that the approach with independence model worked well even when the true correlation model was derived from Clayton's copula. We applied our method to a family-based cohort study of pandemic H1N1 influenza in Taiwan during 2009-2010. Using the proposed method, we investigate the impact of vaccination and family contacts on the incidence of pH1N1 influenza.

Searching for Sharp Drops in the Incidence of Pandemic A/H1N1 Influenza by Single Year of Age

BackgroundDuring the 2009 H1N1 pandemic (pH1N1), morbidity and mortality sparing was observed among the elderly population; it was hypothesized that this age group benefited from immunity to pH1N1 due to cross-reactive antibodies generated from prior infection with antigenically similar influenza viruses. Evidence from serologic studies and genetic similarities between pH1N1 and historical influenza viruses suggest that the incidence of pH1N1 cases should drop markedly in age cohorts born prior to the disappearance of H1N1 in 1957, namely those at least 52–53 years old in 2009, but the precise range of ages affected has not been delineated.Methods and FindingsTo test for any age-associated discontinuities in pH1N1 incidence, we aggregated laboratory-confirmed pH1N1 case data from 8 jurisdictions in 7 countries, stratified by single year of age, sex (when available), and hospitalization status. Using single year of age population denominators, we generated smoothed curves of the weighted risk ratio of pH1N1 incidence, and looked for sharp drops at varying age bandwidths, defined as a significantly negative second derivative. Analyses stratified by hospitalization status and sex were used to test alternative explanations for observed discontinuities. We found that the risk of laboratory-confirmed infection with pH1N1 declines with age, but that there was a statistically significant leveling off or increase in risk from about 45 to 50 years of age, after which a sharp drop in risk occurs until the late fifties. This trend was more pronounced in hospitalized cases and in women and was independent of the choice in smoothing parameters. The age range at which the decline in risk accelerates corresponds to the cohort born between 1951–1959 (hospitalized) and 1953–1960 (not hospitalized).ConclusionsThe reduced incidence of pH1N1 disease in older individuals shows a detailed age-specific pattern consistent with protection conferred by exposure to influenza A/H1N1 viruses circulating before 1957.

Erratum to: Elevation of creatine kinase is associated with worse outcomes in 2009 pH1N1 influenza A infection

Erratum to: Elevation of creatine kinase is associated with worse outcomes in 2009 pH1N1 influenza A infection

In Vitro Reassortment between Endemic H1N2 and 2009 H1N1 Pandemic Swine Influenza Viruses Generates Attenuated Viruses

The pandemic H1N1 (pH1N1) influenza virus was first reported in humans in the spring of 2009 and soon thereafter was identified in numerous species, including swine. Reassortant viruses, presumably arising from the co-infection of pH1N1 and endemic swine influenza virus (SIV), were subsequently identified from diagnostic samples collected from swine. In this study, co-infection of swine testicle (ST) cells with swine-derived endemic H1N2 (MN745) and pH1N1 (MN432) yielded two reassortant H1N2 viruses (R1 and R2), both possessing a matrix gene derived from pH1N1. In ST cells, the reassortant viruses had growth kinetics similar to the parental H1N2 virus and reached titers approximately 2 log10 TCID50/mL higher than the pH1N1 virus, while in A549 cells these viruses had similar growth kinetics. Intranasal challenge of pigs with H1N2, pH1N1, R1 or R2 found that all viruses were capable of infecting and transmitting between direct contact pigs as measured by real time reverse transcription PCR of nasal swabs. Lung samples were also PCR-positive for all challenge groups and influenza-associated microscopic lesions were detected by histology. Interestingly, infectious virus was detected in lung samples for pigs challenged with the parental H1N2 and pH1N1 at levels significantly higher than either reassortant virus despite similar levels of viral RNA. Results of our experiment suggested that the reassortant viruses generated through in vitro cell culture system were attenuated without gaining any selective growth advantage in pigs over the parental lineages. Thus, reassortant influenza viruses described in this study may provide a good system to study genetic basis of the attenuation and its mechanism.

Impact of the 2009 influenza A (H1N1) pandemic on Canadian health care workers: A survey on vaccination, illness, absenteeism, and personal protective equipment

Data are limited on the impact of the 2009 H1N1 influenza A pandemic on health care worker (HCW) vaccination, illness, absenteeism, and personal protective equipment (PPE) use. A survey was completed by HCWs from 14 hospitals participating in the Canadian Nosocomial Infection Surveillance Program who provided direct care to patients with pH1N1 influenza in high-risk units between September and December 2009. Surveys were returned from 986 HCWs (80% nurses, 14% respiratory therapists, and 6% physicians). HCWs working in an intensive care unit (78%) or a designated influenza ward (67%) were more compliant with wearing an N95 respirator for aerosol-generating medical procedures than those working in an emergency department (47%; P < .001). HCWs who worked in health care for >11 years were more compliant with wearing protective eyewear than those who worked for ≤11 years (69% vs 54%; P < .001). A total of 815 HCWs (83%) reported having received the pH1N1 influenza vaccine, and 372 (38%) reported having received the 2009-2010 seasonal influenza vaccine. Influenza-like illness was reported by 236 (24%) HCWs, 170 of whom (72%) reported missing work. Experience working in health care improves PPE use and HCWs in emergency departments should be targeted for interventions to improve PPE compliance. pH1N1 influenza vaccine coverage was high, but seasonal influenza vaccine coverage was low, and significant HCW illness and absenteeism were reported.

Influenza vaccination in the 2009–2010 pandemic season: The experience of primary care physicians

ObjectivesDetermine among a representative sample of pediatricians (Peds), family medicine (FM), and general internal medicine (GIM) physicians in the 2009–2010 influenza season physicians’: 1) practices and experiences with delivery of seasonal and pH1N1 influenza vaccines; and 2) anticipated and experienced barriers. MethodsTwo US national surveys administered 7/2009–10/2009 (before pH1N1 distribution) and 3/2010–6/2010 (after pH1N1 distribution) to 416 Peds, 424 FM and 432 GIM. ResultsOf respondents who received both surveys, 62% (776/1253) completed both. Overall, 98% reported administering seasonal influenza vaccine and 86% pH1N1, with 70% reporting that working with public health in delivery of pH1N1 was a positive experience. Due to limited supplies of pH1N1, 63% of providers reported prioritizing who received vaccine even within high risk groups. Pre-distribution, 71% perceived that patient/parental safety concerns about pH1N1 would be a barrier, and post-distribution 72% perceived it had been a barrier. Physician concern about safety decreased, with 44% reporting safety a barrier pre-distribution and 12% post-distribution (p<0.001). ConclusionsIn the setting of a pandemic most primary care physicians collaborated with public health in delivery of pH1N1. Physicians faced challenges with patient/parent safety concerns about pH1N1 and supply issues with pH1N1 that required physicians to prioritize who received vaccine.

Elevation of creatine kinase is associated with worse outcomes in 2009 pH1N1 influenza A infection

Current medical knowledge lacks specific information regarding creatine kinase (CK) elevation in influenza A pH1N1 (2009) infection. Primary endpoints were correlation between CK at intensive care unit (ICU) admission and ICU mortality. Secondary endpoints were ICU length of stay (LOS), mechanical ventilation (MV), and requirement of renal replacement techniques (RRT). A prospective multicenter register included all adults admitted for severe acute respiratory insufficiency (SARI) with confirmed pH1N1 in 148 ICUs. Clinical data including demographics, comorbidities, laboratory information, organ involvement, and prognostic data were registered. Post hoc classification of subjects was determined according to CK level. Data are expressed as median (interquartile range). Five hundred and five (505) patients were evaluable. Global ICU mortality was 17.8 % without documented differences between breakpoints. CK ≥500 UI/L was documented in 23.8 % of ICU admissions, being associated with greater renal dysfunction: acute kidney injury (AKI) was more frequent (26.1 versus 17.1 %, p < 0.05) and twofold requirement of RRT [11 versus 5.6 %, p < 0.05; odds ratio (OR) = 2.09 (95 % confidence interval [CI] 1.01-4.32)]. Increase of CK ≥1,000 UI/L was associated with two or more quadrant involvement on chest X-ray (63.2 versus 40.2 %, p < 0.01) and increased intubation risk (73.9 versus 56.7 %, p = 0.07) and duration of mechanical ventilation (median 15 days versus 11 days, p < 0.01). As a result, CK ≥1,000 UI/L was associated with 5 extra days of ICU and hospital LOS. CK is a biomarker of severity in pH1N1 infection. Elevation of CK was associated with more complications and increased ICU LOS and healthcare resources.

High mortality in patients with influenza A pH1N1 2009 admitted to a pediatric intensive care unit

To describe the clinical characteristics and outcome of patients admitted to pediatric intensive care with influenza A (pH1N1) 2009 in Argentina. Retrospective observational study. Thirteen pediatric intensive care units in Argentina. One hundred and forty-two patients with confirmed or suspected influenza A (H1N1). None. We included 142 critically ill patients. The median age was 19 months (range, 2-110 months) with 39% of the patients <24 months of age. Ninety-nine patients (70%) had an underlying disease. Influenza A (pH1N1) 2009 infection was confirmed in 90 patients and the remaining 52 had a positive direct immunofluorescence assay for influenza A. The median length of stay in the pediatric intensive care unit was 12 days (range, 2-52 days). One hundred eighteen patients (83%) received invasive mechanical ventilation and 19 patients were treated with noninvasive ventilation; however, seven of the patients receiving noninvasive ventilation later needed mechanical ventilation. Sixty-eight patients died (47%) with the most frequent cause refractory hypoxemia. Multivariate logistic regression analysis showed that age <24 months (odds ratio, 2.87; 2.35-3.93), asthma (odds ratio, 1.34; 1.20-2.91), and respiratory coinfection with respiratory syncytial virus (odds ratio, 2.92; 1.20-4.10) were associated with higher mortality. As expected, mechanical ventilation and treatment with inotropes were also associated with increased mortality. The mortality of children admitted to the pediatric intensive care unit with 2009 pH1N1 influenza was high (47%) in our population. Age <24 months, asthma, respiratory coinfection, need of mechanical ventilation, and treatment with inotropes were predictors of poorer outcome.

Clinical features and risk factors for severe and critical pregnant women with 2009 pandemic H1N1 influenza infection in China.

Background2009 pandemic H1N1 (pH1N1) influenza posed an increased risk of severe illness among pregnant women. Data on risk factors associated with death of pregnant women and neonates with pH1N1 infections are limited outside of developed countries.MethodsRetrospective observational study in 394 severe or critical pregnant women admitted to a hospital with pH1N1 influenza from Sep. 1, 2009 to Dec. 31, 2009. rRT-PCR testing was used to confirm infection. In-hospital mortality was the primary endpoint of this study. Univariable logistic analysis and multivariate logistic regression analysis were used to investigate the potential factors on admission that might be associated with the maternal and neonatal mortality.Results394 pregnant women were included, 286 were infected with pH1N1 in the third trimester. 351 had pneumonia, and 77 died. A PaO2/FiO2 ≤ 200 (odds ratio (OR), 27.16; 95% confidence interval (CI), 2.64-279.70) and higher BMI (i.e. ≥ 30) on admission (OR, 1.26; 95% CI, 1.09 to 1.47) were independent risk factors for maternal death. Of 211 deliveries, 146 neonates survived. Premature delivery (OR, 4.17; 95% CI, 1.19-14.56) was associated neonatal mortality. Among 186 patients who received mechanical ventilation, 83 patients were treated with non-invasive ventilation (NIV) and 38 were successful with NIV. The death rate was lower among patients who initially received NIV than those who were initially intubated (24/83, 28.9% vs 43/87, 49.4%; p = 0.006). Septic shock was an independent risk factor for failure of NIV.ConclusionsSevere hypoxemia and higher BMI on admission were associated with adverse outcomes for pregnant women. Preterm delivery was a risk factor for neonatal death among pregnant women with pH1N1 influenza infection. NIV may be useful in selected pregnant women without septic shock.

Antiviral Therapy and Outcomes of Patients with Pneumonia Caused by Influenza A Pandemic (H1N1) Virus

BackgroundThere is limited data on the clinical outcome of patients with pandemic H1N1 (pH1N1) pneumonia who received oseltamivir treatment, especially when the treatment was administered more than 48 hours after symptom onset.MethodsDuring the pandemic in 2009, a cohort of pH1N1 influenza pneumonia was built in China, and their clinical information was collected systematically, and analyzed with Cox models.Results920 adults and 541 children with pneumonia who didn't receive corticosteroids were analyzed. In-hospital mortality was higher in adults who did not receive antiviral therapy (18.2%) than those with who received oseltamivir ≤ 2days (2.9%), between 2–5 days (4.6%) and >5 days after illness onset (4.9%), p<0.01. A similar trend was observed in pediatric patients. Cox regression showed that at 60 days after symptoms onset, 11 patients (10.8%) who did not receive antivirals died versus 4 (1.8%), 18 (3.3%), and 23 (3.7%) patients whose oseltamivir treatment was started ≤ 2days, between 2–5days, and >5 days, respectively. For males patients, aged ≥ 14 years and baseline PaO2/FiO2<200, oseltamivir administration reduced the mortality risk by 92.1%, 88% and 83.5%, respectively. Higher doses of oseltamivir (>3.8 mg/kg/d) did not improve clinical outcome (mortality, higher dose 2.5% vs standard dose 2.8%, p>0.05).ConclusionsAntiviral therapy might reduce mortality of patients with pH1N1 pneumonia, even when initiated more than 48 hours after onset of illness. Greater protective effects might be in males, patients aged 14–60 years, and patients with PaO2/FiO2<200.

Viral load and epidemiological profile of patients infected by pandemic influenza a (H1N1) 2009 and seasonal influenza a virus in Southern Brazil

Correlation between virologic profile and clinical features of patients infected by influenza virus provides important information for epidemiological control and clinical management of future disease outbreaks. Samples from patients in Southern Brazil, from June to December 2009, were examined and the viral load was correlated with epidemiological data. All samples were analyzed by qRT-PCR for detection of the 2009-pandemic Influenza A (H1N1). Relative viral loads were assessed based on the 2(-ΔCT) method and epidemiological data were obtained for each patient, following ethical policies. A total of 933 samples were positive for pH1N1 (2009) influenza; 172 were positive for seasonal influenza A; 13 were undetermined; 1992 samples were negative for influenza A. Combined molecular and epidemiological data were available for 38 seasonal and 198 pandemic samples. The median viral load was higher in pandemic than in seasonal influenza samples; in patients infected with pH1N1 (2009), viral load associated positively with chills, myalgia and rhinorrhea, and negatively with dyspnea, but no association was observed with other symptoms, nor with clinical conditions such as pregnancy, smoking, immunodepression and co-morbidities. Regarding patients infected with seasonal influenza, viral loads did not show statistically significant association with any of the symptoms. This is the first study in Brazil that examines epidemiological and molecular data from the 2009 influenza pandemic. The results may serve as a basis for developing strategies to control human-to-human infection and viral dissemination, and for implementing effective measures and public health policies against future novel disease outbreaks.

Comparative study of pandemic (H1N1) 2009, swine H1N1, and avian H3N2 influenza viral infections in quails

Quail has been proposed to be an intermediate host of influenza A viruses. However, information on the susceptibility and pathogenicity of pandemic H1N1 2009 (pH1N1) and swine influenza viruses in quails is limited. In this study, the pathogenicity, virus shedding, and transmission characteristics of pH1N1, swine H1N1 (swH1N1), and avian H3N2 (dkH3N2) influenza viruses in quails was examined. Three groups of 15 quails were inoculated with each virus and evaluated for clinical signs, virus shedding and transmission, pathological changes, and serological responses. None of the 75 inoculated (n = 45), contact exposed (n = 15), or negative control (n = 15) quails developed any clinical signs. In contrast to the low virus shedding titers observed from the swH1N1-inoculated quails, birds inoculated with dkH3N2 and pH1N1 shed relatively high titers of virus predominantly from the respiratory tract until 5 and 7 DPI, respectively, that were rarely transmitted to the contact quails. Gross and histopathological lesions were observed in the respiratory and intestinal tracts of quail inoculated with either pH1N1 or dkH3N2, indicating that these viruses were more pathogenic than swH1N1. Sero-conversions were detected 7 DPI in two out of five pH1N1-inoculated quails, three out of five quails inoculated with swH1N1, and four out of five swH1N1-infected contact birds. Taken together, this study demonstrated that quails were more susceptible to infection with pH1N1 and dkH3N2 than swH1N1.

Staphylococcal Enterotoxin B Toxic Shock Syndrome Induced by Community-acquired Methicillin-resistant &lt;i&gt;Staphylococcus aureus&lt;/i&gt; (CA-MRSA)

We herein report a case of toxic shock syndrome (TSS) associated with the 2009 pandemic H1N1 (pH1N1) influenza virus and a community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) infection in a 16-year-old Vietnamese girl. Staphylococcal enterotoxin B (SEB) was detected in the patient's serum, and the level of anti-SEB antibodies was found to be elevated. A flow cytometric analysis showed evidence of activated SEB-reactive Vβ3+ and Vβ12+ T cells. These data suggest that the CA-MRSA-induced activation of SEB-reactive T cells may cause TSS in patients with pH1N1 virus infection. Moreover, this is the first report describing immunological confirmation of SEB contributing directly to TSS in a patient fulfilling the diagnostic criteria of TSS.

A retrospective cross-sectional study of risk factors and clinical spectrum of children admitted to hospital with pandemic H1N1 influenza as compared to influenza A

ObjectiveTo compare risk factors for severe disease as measured by admission to hospital and intensive care unit (ICU) and other clinical outcomes in children with pandemic H1N1 (pH1N1) versus those...

Risk Factors and Outcomes for Pandemic H1N1 Influenza Compared with Seasonal Influenza in Hospitalized Children in China

To compare clinical features and outcomes of children hospitalized in China with pandemic (p)H1N1 between 2009 and 2010 versus seasonal influenza A between 2008 and 2009. Systematic review of laboratory-confirmed admissions to the Children's Hospital, Soochow University (Suzhou, China). Seventy-five children younger than 14 years of age were admitted with pH1N1, 70 with H3N2 and three with seasonal H1N1. With pH1N1, the mean age was older (36 months versus seven months), the length of stay was longer (nine days versus seven days), underlying conditions were more common (29% versus 15%), anemia was more common (11% versus 0%) (P<0.05), with trends toward more secondary bacterial pneumonia and intensive care unit care, compared with seasonal influenza. Two of the 75 children with pH1N1 died versus no deaths in children with seasonal influenza. None of the children had received pH1N1, seasonal influenza, conjugated pneumococal or Haemophilus influenzae b vaccines. In China, children hospitalized with pH1N1 influenza differed from case series in Canada, Argentina and the United States, suggesting that locale, background and health care system influenced the presentation and outcomes of pandemic and seasonal influenza.

2009 pandemic H1N1 influenza virus elicits similar clinical course but differential host transcriptional response in mouse, macaque, and swine infection models

BackgroundThe 2009 pandemic H1N1 influenza virus emerged in swine and quickly became a major global health threat. In mouse, non human primate, and swine infection models, the pH1N1 virus efficiently replicates in the lung and induces pro-inflammatory host responses; however, whether similar or different cellular pathways were impacted by pH1N1 virus across independent infection models remains to be further defined. To address this we have performed a comparative transcriptomic analysis of acute phase responses to a single pH1N1 influenza virus, A/California/04/2009 (CA04), in the lung of mice, macaques and swine.ResultsDespite similarities in the clinical course, we observed differences in inflammatory molecules elicited, and the kinetics of their gene expression changes across all three species. We found genes associated with the retinoid X receptor (RXR) signaling pathway known to control pro-inflammatory and metabolic processes that were differentially regulated during infection in each species, though the heterodimeric RXR partner, pathway associated signaling molecules, and gene expression patterns varied among the three species.ConclusionsBy comparing transcriptional changes in the context of clinical and virological measures, we identified differences in the host transcriptional response to pH1N1 virus across independent models of acute infection. Antiviral resistance and the emergence of new influenza viruses have placed more focus on developing drugs that target the immune system. Underlying overt clinical disease are molecular events that suggest therapeutic targets identified in one host may not be appropriate in another.

Serological Survey of the Novel Influenza A H1N1 in Inner City Winnipeg, Manitoba, 2009

Little is known about the determinants of pandemic H1N1 (pH1N1) infection in Canada among low-income, inner city populations. To inform future influenza planning, the seroprevalence of pH1N1 antibodies among inner city clinic attendees in Winnipeg (Manitoba) according to sociodemographic and risk factor characteristics were estimated and vaccination rates were explored. Adults presenting to three inner city community clinics in Winnipeg from October 2009 to December 2009 were recruited as study participants (n=458). A questionnaire was administered to collect demographic, risk factor and symptom information, and a venous blood sample was collected for hemagglutination inhibition assay testing to detect the presence of antibodies against pH1N1. Approximately one-half (53%) of the study participants reported an annual household income of <$10,000/year, and 65% identified as Aboriginal. pH1N1 positivity was 5.7% among those enrolled early in the study and 15.5% among those enrolled later in the study. Positivity was higher among participants who were female, Aboriginal and in contact with children ≤5 years of age. The overall pH1N1 vaccination rate was 28%. pH1N1 positivity was high among low-income adults accessing clinics in Winnipeg's inner city compared with the general population. Of further concern were the low rates of uptake of both seasonal and pH1N1 influenza vaccinations. When planning for future influenza outbreaks, it is important to incorporate strategies for the prevention, control, and care of influenza among low-income and inner city adults.

Transmissibility of the 2009 H1N1 pandemic in remote and isolated Canadian communities: a modelling study

ObjectivesDuring the first wave of the 2009 influenza pH1N1, disease burden was distributed in a geographically heterogeneous fashion. It was particularly high in some remote and isolated Canadian communities when...

Successful Treatment of Novel H1N1 Influenza related Fulminant Myocarditis with Extracorporeal Life Support

The prevalence of myocardial involvement in influenza infection ranges from 0% to 12%. The 2009 pH1N1 influenza virus, formerly known as swine flu, first appeared in Mexico and the United States of America in March and April 2009 and has swept the globe with unprecedented speed. We report a case of fulminant myocarditis associated with this virus treated successfully using extra-corporal membrane oxygenator.