Pdm09 Virus Infection Research Articles

Clinicopathologic, Immunohistochemical, and Ultrastructural Findings of a Fatal Case of Middle East Respiratory Syndrome Coronavirus Infection in the United Arab Emirates, April 2014

Middle East respiratory syndrome coronavirus (MERS-CoV) infection causes an acute respiratory illness and is associated with a high case fatality rate; however, the pathogenesis of severe and fatal MERS-CoV infection is unknown. We describe the histopathologic, immunohistochemical, and ultrastructural findings from the first autopsy performed on a fatal case of MERS-CoV in the world, which was related to a hospital outbreak in the United Arab Emirates in April 2014. The main histopathologic finding in the lungs was diffuse alveolar damage. Evidence of chronic disease, including severe peripheral vascular disease, patchy cardiac fibrosis, and hepatic steatosis, was noted in the other organs. Double staining immunoassays that used anti–MERS-CoV antibodies paired with immunohistochemistry for cytokeratin and surfactant identified pneumocytes and epithelial syncytial cells as important targets of MERS-CoV antigen; double immunostaining with dipeptidyl peptidase 4 showed colocalization in scattered pneumocytes and syncytial cells. No evidence of extrapulmonary MERS-CoV antigens were detected, including the kidney. These results provide critical insights into the pathogenesis of MERS-CoV in humans.

Production impact of influenza A(H1N1)pdm09 virus infection on fattening pigs in Norway.

Newly emerged influenza A(H1N1)pdm09 virus infection in Norwegian pigs, although often observed in a subclinical form, can lower the pig's growth performance by reducing feed efficiency in terms of a poorer feed conversion ratio. Infected pigs would consume more feed and require protracted production time to reach market weight. In our observational longitudinal study, growth performance data from 728 control pigs and 193 infected pigs with known viral shedding time points were analyzed using mixed linear regression models to give estimates of the marginal effects of infection. Gaussian curves describing the variability of the estimates at the individual pig level formed the fundamental inputs to our stochastic models. The models were constructed to simulate the summed negative effects of the infection at the batch level of 150 fattening pigs growing from 33 to 100 kg. Other inputs of variability and uncertainty were 1) batch transmission points, 2) pig infection points to reflect the disease transmission dynamics of the virus, and 3) final prevalence of infected pigs in the batch. Monte Carlo random sampling gave 5,000 estimates on the outputs of the marginal effects for each pig. These results were summed up to provide estimates for a batch size of 150 pigs. This figure was adjusted by our final prevalence distribution function, which was also derived from the longitudinal study with 12 cohorts of infected pigs. For a 150-fattening-pig herd randomly selected from the population, the marginal effects of the infection were 1) 835 kg (fifth percentile) to 1,350 kg (95th percentile) increased feed intake and 2) 194 (fifth percentile) to 334 (95th percentile) pig days in excess of expected figures for an uninfected batch. A batch infected during growth phase 3 (81 to 100 kg BW) gave the worst results since the longitudinal study showed that a pig infected during growth phase 3 required more feed and a greater protracted production time compared to younger infected pigs. Sensitivity analysis showed that final prevalence had the greatest impact on the conditional mean and variation of the marginal effects of infections. Batch transmission point was the next most influential factor. Lowering the final prevalence and preventing older fattening pigs from being infected will have the greatest benefit in saving feed cost and reducing delay in getting the pigs to the market.

Impact of neuraminidase inhibitors on influenza A(H1N1)pdm09-related pneumonia: an individual participant data meta-analysis.

BackgroundThe impact of neuraminidase inhibitors (NAIs) on influenza‐related pneumonia (IRP) is not established. Our objective was to investigate the association between NAI treatment and IRP incidence and outcomes in patients hospitalised with A(H1N1)pdm09 virus infection.MethodsA worldwide meta‐analysis of individual participant data from 20 634 hospitalised patients with laboratory‐confirmed A(H1N1)pdm09 (n = 20 021) or clinically diagnosed (n = 613) ‘pandemic influenza’. The primary outcome was radiologically confirmed IRP. Odds ratios (OR) were estimated using generalised linear mixed modelling, adjusting for NAI treatment propensity, antibiotics and corticosteroids.ResultsOf 20 634 included participants, 5978 (29·0%) had IRP; conversely, 3349 (16·2%) had confirmed the absence of radiographic pneumonia (the comparator). Early NAI treatment (within 2 days of symptom onset) versus no NAI was not significantly associated with IRP [adj. OR 0·83 (95% CI 0·64–1·06; P = 0·136)]. Among the 5978 patients with IRP, early NAI treatment versus none did not impact on mortality [adj. OR = 0·72 (0·44–1·17; P = 0·180)] or likelihood of requiring ventilatory support [adj. OR = 1·17 (0·71–1·92; P = 0·537)], but early treatment versus later significantly reduced mortality [adj. OR = 0·70 (0·55–0·88; P = 0·003)] and likelihood of requiring ventilatory support [adj. OR = 0·68 (0·54–0·85; P = 0·001)].ConclusionsEarly NAI treatment of patients hospitalised with A(H1N1)pdm09 virus infection versus no treatment did not reduce the likelihood of IRP. However, in patients who developed IRP, early NAI treatment versus later reduced the likelihood of mortality and needing ventilatory support.

A Clinical Comparison of Hospitalized Pediatric Patients with Influenza A(H1N1)Pdm09 Virus Infection of the Years 2009/10 and 2012/13

A Clinical Comparison of Hospitalized Pediatric Patients with Influenza A(H1N1)Pdm09 Virus Infection of the Years 2009/10 and 2012/13

Characterization of the Localized Immune Response in the Respiratory Tract of Ferrets following Infection with Influenza A and B Viruses.

The burden of infection with seasonal influenza viruses is significant. Each year is typically characterized by the dominance of one (sub)type or lineage of influenza A or B virus, respectively. The incidence of disease varies annually, and while this may be attributed to a particular virus strain or subtype, the impacts of prior immunity, population differences, and variations in clinical assessment are also important. To improve our understanding of the impacts of seasonal influenza viruses, we directly compared clinical symptoms, virus shedding, and expression of cytokines, chemokines, and immune mediators in the upper respiratory tract (URT) of ferrets infected with contemporary A(H1N1)pdm09, A(H3N2), or influenza B virus. Gene expression in the lower respiratory tract (LRT) was also assessed. Clinical symptoms were minimal. Overall cytokine/chemokine profiles in the URT were consistent in pattern and magnitude between animals infected with influenza A and B viruses, and peak expression levels of interleukin-1α (IL-1α), IL-1β, IL-6, IL-12p40, alpha interferon (IFN-α), IFN-β, and tumor necrosis factor alpha (TNF-α) mRNAs correlated with peak levels of viral shedding. MCP1 and IFN-γ were expressed after the virus peak. Granzymes A and B and IL-10 reached peak expression as the virus was cleared and seroconversion was detected. Cytokine/chemokine gene expression in the LRT following A(H1N1)pdm09 virus infection reflected the observations seen for the URT but was delayed 2 or 3 days, as was virus replication. These data indicate that disease severities and localized immune responses following infection with seasonal influenza A and B viruses are similar, suggesting that other factors are likely to modulate the incidence and impact of seasonal influenza. Both influenza A and B viruses cocirculate in the human population, and annual influenza seasons are typically dominated by an influenza A virus subtype or an influenza B virus lineage. Surveillance data indicate that the burden of disease is higher in some seasons, yet it is unclear whether this is due to specific virus strains or to other factors, such as cross-reactive immunity or clinical definitions of influenza. We directly compared disease severities and localized inflammatory responses to different seasonal influenza virus strains, including the 2009 pandemic strain, in healthy naive ferrets. We found that the disease severities and the cytokine and chemokine responses were similar irrespective of the seasonal strain or the location of the infection in the respiratory tract. This suggests that factors other than the immune response to a particular virus (sub)type contribute to the variable impact of influenza virus infection in a population.

TNF, IL6, and IL1B Polymorphisms Are Associated with Severe Influenza A (H1N1) Virus Infection in the Mexican Population.

BackgroundHypercytokinemia is the main immunopathological mechanism contributing to a more severe clinical course in influenza A (H1N1) virus infections. Most patients infected with the influenza A (H1N1) pdm09 virus had increased systemic levels of pro-inflammatory cytokines; including interleukin IL-6, IL-8, and tumor necrosis factor-alpha (TNF-α). We propose that single-nucleotide polymorphisms (SNPs) in the promoter regions of pro-inflammatory genes are associated with the severity of influenza A (H1N1) pdm09 virus infection.Methods145 patients with influenza A (H1N1) (pA/H1N1), 133 patients with influenza-like illness (ILI), and 360 asymptomatic healthy contacts (AHCs) were included. Eleven SNPs were genotyped in six genes (TNF, LT, IL1B, IL6, CCL1, and IL8) using real-time PCR; the ancestral genotype was used for comparison. Genotypes were correlated with 27 clinical severity variables. Ten cytokines (GM-CSF, TNF-α, IL-2, IL-1β, IL-6, IL-8, IFN-γ, IL-10, IL-5, and IL-4) were measured on a Luminex 100.ResultsThe IL6 rs1818879 (GA) heterozygous genotype was associated with severe influenza A (H1N1) virus infection (odds ratio [OR] = 5.94, 95% confidence interval [CI] 3.05–11.56), and two IL1B SNPs, rs16944 AG and rs3136558 TC, were associated with a decreased risk of infection (OR = 0.52 and OR = 0.51, respectively). Genetic susceptibility was determined (pA/H1N1 vs. AHC): the LTA rs909253 TC heterozygous genotype conferred greater risk (OR = 1.9), and a similar association was observed with the IL1B rs3136558 CC genotype (OR = 1.89). Additionally, severely ill patients were compared with moderately ill patients. The TNF-238 GA genotype was associated with an increased risk of disease severity (OR = 16.06, p = 0.007). Compared with ILIs, patients with severe pA/H1N1 infections exhibited increased serum IL-5 (p <0.001) and IL-6 (p = 0.007) levels.ConclusionsThe TNF gene was associated with disease severity, whereas IL1B and IL6 SNPs were associated with influenza A (H1N1) virus infection.

Post-pandemic influenza A (H1N1) 2009 virus infection in pregnant women in Ceará, Brazil.

ObjectiveThe aim of this study was to present results of the post-pandemic phase of A(H1N1)pdm09 virus infection in pregnant women in Ceará, Brazil, during the January–June 2012 influenza season.ResultsOne hundred and fifty-four nasopharyngeal swab samples were collected from pregnant women admitted to hospitals with suspected severe acute respiratory infection (SARI). Fifty-three (34·4%) had laboratory-confirmed A(H1N1)pdm09 virus infection with 15 (28·3%) outpatients and 38 (71·7%) hospitalized. Five (9·4%) women were in the first trimester of pregnancy, 20 (37·7%) in the second trimester of pregnancy, and 24 (45·2%) in the third trimester of pregnancy. Three had no information about the time of pregnancy. Six samples from newborns were also analyzed, of which three were nasopharyngeal swab positive for A(H1N1)pdm09. These swabs were collected immediately after birth, with the exception of one that was collected on the day after birth.ConclusionOur findings suggest that transplacental transfer of influenza viruses could occur as a result of severe illness in pregnancy. It is therefore important to encourage women to be vaccinated against influenza in order to avoid pregnancy complications.

Pregnancy-Related Mortality Resulting From Influenza in the United States During the 2009-2010 Pandemic.

To estimate the burden of pregnancy-related mortality resulting from influenza A (H1N1)pdm09 virus infection during the 2009-2010 pandemic influenza season. Data from the Centers for Disease Control and Prevention's Pregnancy Mortality Surveillance System were used to identify women whose death during or shortly after pregnancy was attributed or likely attributed to the influenza A (H1N1)pdm09 virus from April 15, 2009, through June 30, 2010. We report the characteristics of these women and enumerate cases resulting in death as the pandemic began, peaked, and resolved. During the pandemic season, we identified 915 pregnancy-related deaths and 4,911,297 live births. Seventy-five (8.2%) women died as a result of confirmed influenza A (H1N1)pdm09 infection deaths and 34 (3.7%) women as a result of possible influenza A (H1N1)pdm09 infection deaths. The pregnancy-related mortality ratio for confirmed and possible (combined) influenza A (H1N1)pdm09 infection deaths was 2.2 per 100,000 live births. Most deaths occurred during the 2009 calendar year with the peak of the distribution of deaths over time occurring in October 2009. Twelve percent of pregnancy-related deaths were attributed to confirmed or possible influenza A (H1N1)pdm09 infection during the 2009-2010 pandemic season. Because prediction of pandemics is difficult, planning for prevention of influenza and care for those women affected are critical for preventing associated severe maternal morbidity and mortality. III.

Clinical findings in 10 children with H275Y influenza A(H1N1)pdm09 virus infection.

Little is known about the clinical effectiveness of neuraminidase inhibitors against H275Y influenza A(H1N1)pdm09 virus. A cluster of H275Y influenza A(H1N1)pdm09 virus with cross-resistance to oseltamivir and peramivir was detected among untreated community patients in Hokkaido, Japan, during the 2013-2014 influenza season. This was a retrospective observational study. Specimens from nasopharyngeal swabs underwent rapid testing and single-nucleotide polymorphism identification on real-time polymerase chain reaction. We collected clinical data from the H275Y group and a 275H wild-type comparison group. All children were given one of four neuraminidase inhibitors. Twenty-eight children infected with influenza A(H1N1)pdm09 virus were analyzed. Ten viruses had the H275Y substitution, while the other 18 had wild-type 275H. Mean fever duration after treatment and after onset was 25.3 h (95%CI: 14.1-36.5) and 48.9 h (95%CI: 34.4-63.3) in the H275Y group, respectively, and 26.1 h (95%CI: 18.7-33.6) and 46.3 h (95%CI: 35.7-56.8) in the 275H group, respectively. In the H275Y group, three patients were treated with oseltamivir, one with peramivir, five with zanamivir, and one with laninamivir. All of them had mild symptoms and received only outpatient care. Fever duration was 7.5-21.0 h and 18.0-66.0 h after treatment and after onset, respectively, in the patients treated with oseltamivir and peramivir, and 20.5-42.0 h and 42.0-88.0 h, respectively, in those treated with zanamivir and laninamivir. Fever in the H275Y children treated with oseltamivir and peramivir resolved rapidly during the 2013-2014 influenza season.

TGF-β Blood Levels Distinguish Between Influenza A (H1N1)pdm09 Virus Sepsis and Sepsis due to Other Forms of Community-Acquired Pneumonia.

There is a strong interest in finding adequate biomarkers to aid in the diagnosis and prognosis of influenza A (H1N1)pdm09 virus infection. In this study, serum levels of inflammatory cytokines and laboratory markers were evaluated to assess their usefulness as biomarkers of influenza A (H1N1)pdm09 and their association with fatal cases. Serum samples of consecutive patients with a clinical presentation suggestive of influenza A (H1N1)pdm09 and progression to sepsis were evaluated. Serum inflammatory cytokines and routine laboratory tests were performed and correlated with positivity for influenza A (H1N1)pdm09 influenza by real time reverse transcription polymerase chain reaction and the results of three clinical severity scores (Sequential Organ Failure Assessment [SOFA], CURB-65, and Acute Physiology and Chronic Health Evaluation II [APACHE II]). High SOFA scores and some of its individual components, but not CURB-65 or APACHE II scores, correlate with fatal cases regardless of etiology. Total and unconjugated bilirubin, Ca(++), Cl(-), prothrombin times, and partial thromboplastin times discriminate influenza A (H1N1)pdm09 from other causes of community-acquired pneumonia. High levels of IL-8, IL-10, and IL-17 were increased in influenza A (H1N1)pdm09 patients when compared with controls (p<0.05). IL-6 levels were significantly elevated in influenza A (H1N1)pdm09 patients and non-(H1N1)pdm09 patients when compared with controls (p<0.05). TGF-β serum levels discern between healthy controls, influenza A (H1N1)pdm09 patients, and patients with other causes of community-acquired pneumonia. TGF-β levels were negatively correlated with SOFA on admission in influenza A (H1N1)pdm09 patients. TGF-β levels are a useful tool for differentiating influenza A (H1N1)pdm09 from other causes of pneumonia progressing to sepsis.

Severity of influenza A(H1N1) illness and emergence of D225G variant, 2013-14 influenza season, Florida, USA.

Despite a regional decline in influenza A(H1N1)pdm09 virus infections during 2013–14, cases at a Florida hospital were more severe than those during 2009–10. Examined strains had a hemagglutinin polymorphism associated with enhanced binding to lower respiratory tract receptors. Genetic changes in this virus must be monitored to predict the effect of future pandemic viruses.

Identification of amino acid substitutions supporting antigenic change of influenza A(H1N1)pdm09 viruses.

The majority of currently circulating influenza A(H1N1) viruses are antigenically similar to the virus that caused the 2009 influenza pandemic. However, antigenic variants are expected to emerge as population immunity increases. Amino acid substitutions in the hemagglutinin protein can result in escape from neutralizing antibodies, affect viral fitness, and change receptor preference. In this study, we constructed mutants with substitutions in the hemagglutinin of A/Netherlands/602/09 in an attenuated backbone to explore amino acid changes that may contribute to emergence of antigenic variants in the human population. Our analysis revealed that single substitutions affecting the loop that consists of amino acid positions 151 to 159 located adjacent to the receptor binding site caused escape from ferret and human antibodies elicited after primary A(H1N1)pdm09 virus infection. The majority of these substitutions resulted in similar or increased replication efficiency in vitro compared to that of the virus carrying the wild-type hemagglutinin and did not result in a change of receptor preference. However, none of the substitutions was sufficient for escape from the antibodies in sera from individuals that experienced both seasonal and pandemic A(H1N1) virus infections. These results suggest that antibodies directed against epitopes on seasonal A(H1N1) viruses contribute to neutralization of A(H1N1)pdm09 antigenic variants, thereby limiting the number of possible substitutions that could lead to escape from population immunity. Influenza A viruses can cause significant morbidity and mortality in humans. Amino acid substitutions in the hemagglutinin protein can result in escape from antibody-mediated neutralization. This allows the virus to reinfect individuals that have acquired immunity to previously circulating strains through infection or vaccination. To date, the vast majority of A(H1N1)pdm09 strains remain antigenically similar to the virus that caused the 2009 influenza pandemic. However, antigenic variants are expected to emerge as a result of increasing population immunity. We show that single amino acid substitutions near the receptor binding site were sufficient to escape from antibodies specific for A(H1N1)pdm09 viruses but not from antibodies elicited in response to infections with seasonal A(H1N1) and A(H1N1)pdm09 viruses. This study identified substitutions in A(H1N1)pdm09 viruses that support escape from population immunity but also suggested that the number of potential escape variants is limited by previous exposure to seasonal A(H1N1) viruses.

Comparison of serum hemagglutinin and neuraminidase inhibition antibodies after 2010-2011 trivalent inactivated influenza vaccination in healthcare personnel.

Background. Most inactivated influenza vaccines contain purified and standardized hemagglutinin (HA) and residual neuraminidase (NA) antigens. Vaccine-associated HA antibody responses (hemagglutination inhibition [HAI]) are well described, but less is known about the immune response to the NA.Methods. Serum of 1349 healthcare personnel (HCP) electing or declining the 2010–2011 trivalent-inactivated influenza vaccine ([IIV3], containing A/California/7/2009 p(H1N1), A/Perth/16/2009 [H3N2], B/Brisbane/60/2008 strains) were tested for NA-inhibiting (NAI) antibody by a modified lectin-based assay using pseudotyped N1 and N2 influenza A viruses with an irrelevant (H5) HA. Neuraminidase-inhibiting and HAI antibody titers were evaluated approximately 30 days after vaccination and end-of-season for those with polymerase chain reaction (PCR)-confirmed influenza infection.Results. In 916 HCP (68%) receiving IIV3, a 2-fold increase in N1 and N2 NAI antibody occurred in 63.7% and 47.3%, respectively. Smaller responses occurred in HCP age >50 years and those without prior 2009–2010 IIV3 nor monovalent A(H1N1)pdm09 influenza vaccinations. Forty-four PCR-confirmed influenza infections were observed, primarily affecting those with lower pre-exposure HAI and NAI antibodies. Higher pre-NAI titers correlated with shorter duration of illness for A(H1N1)pdm09 virus infections.Conclusions. Trivalent-inactivated influenza vaccine is modestly immunogenic for N1 and N2 antigens in HCP. Vaccines eliciting robust NA immune responses may improve efficacy and reduce influenza-associated morbidity.

Emergence of influenza A (H1N1) PDM09 in the remote Islands of India--a molecular approach.

A disease outbreak of A (H1N1) PDM09 was reported in Andaman and Nicobar islands in 2009 with an attack rate of 33.5% among settler population and 26.3% among the aboriginal Nicobarese tribe. During the ongoing outbreak of A (H1N1) PDM09 disease in different parts of the world, a subject working in Dubai city of Saudi Arabia, came to Port Blair, following which the pandemic triggered for the first time in these Islands. During the period August 2009 to January 2011, 30 confirmed cases of Influenza A (H1N1) PDM09 virus infection was detected. To understand the genetic relationship, the NA gene sequences of the viruses were phylogenetically analysed together along with the virus sequence isolated from other parts of the world. Formation of multiple clusters were observed, with the sequences of Andaman Islands, mainland India, Mexico, Saudi Arabia and few other counties clustering together. The sequence analysis data revealed that there was no specific mutation conferring resistance to oseltamivir among the Andaman A (H1N1) PDM09 virus isolates. The result of phylogenetic analysis have also revealed that the A (H1N1) PDM09 virus might have spread in these remote Islands of India via the subject from Saudi Arabia/Dubai. A (H1N1) PDM09 Influenza outbreak have highlighted the need to strengthen the region-specific pandemic preparedness plans and surveillance strategies.

Adverse effects of Influenza A(H1N1)pdm09 virus infection on growth performance of Norwegian pigs - a longitudinal study at a boar testing station.

BackgroundInfluenza A(H1N1)pdm09 virus infection in Norwegian pigs was largely subclinical. This study tested the hypothesis that the infection causes negligible impact on pigs’ growth performance in terms of feed conversion efficiency, daily feed intake, daily growth, age on reaching 100 kg bodyweight and overall feed intake. A sample of 1955 pigs originating from 43 breeding herds was classified into five infection status groups; seronegative pigs (n = 887); seropositive pigs (n = 874); pigs positive for virus at bodyweight between 33 kg and 60 kg (n = 123); pigs positive for virus at bodyweight between 61 kg and 80 kg (n = 34) and pigs positive for virus at bodyweight between 81 kg and 100 kg (n = 37). Each pig had daily recordings of feed intake and bodyweight from 33 kg to 100 kg. Marginal effects of the virus infection on the outcomes were estimated by multi-level linear regression, which accounted for known fixed effects (breed, birthdate, average daily feed intake and growth phase) and random effects (cluster effects of pig and herd).ResultsThe seropositive and virus positive pigs had decreased (P value<0.05) growth performance compared to seronegative pigs even though feed intake was not decreased. Reduced feed conversion efficiency led to lower average daily growth, additional feed requirement and longer time needed to reach the 100 kg bodyweight. The effects were more marked (P value<0.03) in pigs infected at a younger age and lasted a longer period. Despite increased feed intake observed, their growth rates were lower and they took more time to reach 100 kg bodyweight compared to the seronegative pigs.ConclusionOur study rejected the null hypothesis that the virus infection had negligible adverse effects on growth performance of Norwegian pigs.

Influenza A(H1N1)pdm09 resistance and cross-decreased susceptibility to oseltamivir and zanamivir antiviral drugs.

Neuraminidase inhibitors (NAIs) oseltamivir and zanamivir are currently the only effective antiviral drugs available worldwide for the management of influenza. The potential development of resistance is continually threatening their use, rationalizing and highlighting the need for a close and sustained evaluation of virus susceptibility. This study aimed to analyze and characterize the phenotypic and genotypic NAIs susceptibility profiles of A(H1N1)pdm09 viruses circulating in Portugal from 2009 to 2010/2011. A total of 144 cases of A(H1N1)pdm09 virus infection from community and hospitalized patients were studied, including three suspected cases of clinical resistance to oseltamivir. Oseltamivir resistance was confirmed for two of the suspected cases. Neuraminidase (NA) H275Y resistant marker was found in viruses from both cases but for one it was only present in 26.2% of virus population, raising questions about the minimal percentage of resistant virus that should be considered relevant. Cross-decreased susceptibility to oseltamivir and zanamivir (2-4 IC50 fold-change) was detected on viruses from two potentially linked community patients from 2009. Both viruses harbored the NA I223V mutation. NA Y155H mutation was found in 18 statistical non-outlier viruses from 2009, having no impact on virus susceptibility. The mutations at NA N369K and V241I may have contributed to the significantly higher baseline IC50 value obtained to oseltamivir for 2010/2011 viruses, compared to viruses from the pandemic period. These results may contribute to a better understanding of the relationship between phenotype and genotype, which is currently challenging, and to the global assessment of A(H1N1)pdm09 virus susceptibility profile and baseline level to NAIs.

Outcomes of influenza A(H1N1)pdm09 virus infection: results from two international cohort studies.

BackgroundData from prospectively planned cohort studies on risk of major clinical outcomes and prognostic factors for patients with influenza A(H1N1)pdm09 virus are limited. In 2009, in order to assess outcomes and evaluate risk factors for progression of illness, two cohort studies were initiated: FLU 002 in outpatients and FLU 003 in hospitalized patients.Methods and FindingsBetween October 2009 and December 2012, adults with influenza-like illness (ILI) were enrolled; outpatients were followed for 14 days and inpatients for 60 days. Disease progression was defined as hospitalization and/or death for outpatients, and hospitalization for >28 days, transfer to intensive care unit (ICU) if enrolled from general ward, and/or death for inpatients. Infection was confirmed by RT-PCR. 590 FLU 002 and 392 FLU 003 patients with influenza A (H1N1)pdm09 were enrolled from 81 sites in 17 countries at 2 days (IQR 1–3) and 6 days (IQR 4–10) following ILI onset, respectively. Disease progression was experienced by 29 (1 death) outpatients (5.1%; 95% CI: 3.4–7.2%) and 80 inpatients [death (32), hospitalization >28 days (43) or ICU transfer (20)] (21.6%; 95% CI: 17.5–26.2%). Disease progression (death) for hospitalized patients was 53.1% (26.6%) and 12.8% (3.8%), respectively, for those enrolled in the ICU and general ward. In pooled analyses for both studies, predictors of disease progression were age, longer duration of symptoms at enrollment and immunosuppression. Patients hospitalized during the pandemic period had a poorer prognosis than in subsequent seasons.ConclusionsPatients with influenza A(H1N1)pdm09, particularly when requiring hospital admission, are at high risk for disease progression, especially if they are older, immunodeficient, or admitted late in infection. These data reinforce the need for international trials of novel treatment strategies for influenza infection and serve as a reminder of the need to monitor the severity of seasonal and pandemic influenza epidemics globally.Trial RegistrationClinicalTrials.gov Identifiers: FLU 002- NCT01056354, FLU 003- NCT01056185.

IgM, IgG, and IgA antibody responses to influenza A(H1N1)pdm09 hemagglutinin in infected persons during the first wave of the 2009 pandemic in the United States.

The novel influenza A(H1N1)pdm09 virus caused an influenza pandemic in 2009. IgM, IgG, and IgA antibody responses to A(H1N1)pdm09 hemagglutinin (HA) following A(H1N1)pdm09 virus infection were analyzed to understand antibody isotype responses. Age-matched control sera collected from U.S. residents in 2007 and 2008 were used to establish baseline levels of cross-reactive antibodies. IgM responses often used as indicators of primary virus infection were mainly detected in young patient groups (≤5 years and 6 to 15 years old), not in older age groups, despite the genetic and antigenic differences between the HA of A(H1N1)pdm09 virus and pre-2009 seasonal H1N1 viruses. IgG and IgA responses to A(H1N1)pdm09 HA were detected in all age groups of infected persons. In persons 17 to 80 years old, paired acute- and convalescent-phase serum samples demonstrated ≥4-fold increases in the IgG and IgA responses to A(H1N1)pdm09 HA in 80% and 67% of A(H1N1)pdm09 virus-infected persons, respectively. The IgG antibody response to A(H1N1)pdm09 HA was cross-reactive with HAs from H1, H3, H5, and H13 subtypes, suggesting that infections with subtypes other than A(H1N1)pdm09 might result in false positives by enzyme-linked immunosorbent assay (ELISA). Lower sensitivity compared to hemagglutination inhibition and microneutralization assays and the detection of cross-reactive antibodies against homologous and heterologous subtype are major drawbacks for the application of ELISA in influenza serologic studies.

Relationships between A(H1N1)pdm09 influenza infection and infections with other respiratory viruses

BackgroundA(H1N1)pdm09, a new influenza pandemic virus emerged in 2009. The A(H1N1)pdm09 infection had several unique characteristics which included rapid transmissibility and high morbidity in obese individuals, pregnant women and individuals suffering from chronic diseases.ObjectivesTo study the relationships between A(H1N1)pdm09 influenza infection and infections with other respiratory viruses such as respiratory syncytial virus (RSV), human metapneumo virus (hMPV), adenovirus and seasonal influenza.MethodsSamples (nasopharyngeal swabs or aspirates) collected between 2007 until 2012 from patients of various ages that were hospitalized due to respiratory virus infections were analyzed for the presence of various respiratory viruses, using qRT-PCR.ResultsIn 2009–2010, when the pandemic influenza A(H1N1)pdm09 first appeared, two major infection peaks were noted and individuals of various ages were infected. Following the decline of the A(H1N1)pdm09 virus infection, the percentages of patients infected with adenovirus and hMPV increased, while infection frequency with RSV B and with seasonal influenza virus decreased. Furthermore, RSV infections were delayed and very few percentages of patients were co-infected with more than one virus. Interestingly, the A(H1N1)pdm09 virus lost its dominancy when it reappeared in the winter of 2010–2011, and at this time, only the incidence of RSV infections was affected by the A(H1N1)pdm09 virus.ConclusionsThe A(H1N1)pdm09 virus had distinct effects on other respiratory viruses when it first appeared versus later, when it evolved from being a pandemic to a seasonal virus.

Evidence for Subclinical Influenza A(H1N1)pdm09 Virus Infection among Dogs in Guangdong Province, China

During 2012, we identified sampled dogs with elevated levels of antibodies (≥1:40) against A(H1N1)pdm09 virus by using a hemagglutination inhibition (HI) assay (seroprevalence, 24.7%) and a microneutralization (MN) assay (seroprevalence, 10.8%). These high seroprevalences of A(H1N1)pdm09 among dogs without clinical signs of influenza support the premise that dogs may play a role in the human influenza ecology in China.