Rate and influence of respiratory virus co-infection on pandemic (H1N1) influenza disease

Objectives

Many patients with influenza have more than one viral agent with co-infection frequencies reported as high as 20%. The impact of respiratory virus copathogens on influenza disease is unclear. We sought to determine if respiratory virus co-infection with pandemic H1N1 altered clinical disease.

Methods

Respiratory samples from 229 and 267 patients identified with and without H1N1 influenza respectively were screened for the presence of 13 seasonal respiratory viruses by multiplex RT-PCR. Disease severity between coinfected and monoinfected H1N1 patients were quantified using a standardized clinical severity scale. Influenza viral load was calculated by quantitative RT-PCR.

Results

Thirty (13.1%) influenza samples screened positive for the presence of 31 viral copathogens. The most prominent copathogens included rhinovirus (61.3%), and coronaviruses (16.1%). Median clinical severity of both monoinfected and coinfected groups were 1. Patients coinfected with rhinovirus tended to have lower clinical severity (median 0), whereas non-rhinovirus co-infections had substantially higher clinical severity (median 2). No difference in H1N1 viral load was observed between coinfected and monoinfected groups.

Conclusions

Respiratory viruses co-infect patients with influenza disease. Patients coinfected with rhinovirus had less severe disease while non-rhinovirus co-infections were associated with substantially higher severity without changes in influenza viral titer.     

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

Background

A(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.

Objectives

To 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.

Methods

Samples (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.

Results

In 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.

Conclusions

The 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.     

Viral detection profile in children with severe acute respiratory infection

Objectives

The role of viral co-detection in children with severe acute respiratory infection is not clear. We described the viral detection profile and its association with clinical characteristics in children admitted to the Pediatric Intensive Care Unit (PICU) during the 2009 influenza A(H1N1) pandemic.

Respiratory viral infections among hospitalized adults: experience of a single tertiary healthcare hospital

Background

Following the 2009 H1N1 pandemic, there have been a large number of studies focusing on the epidemiology and outcomes of influenza A infection; however, there have been fewer studies focused on other respiratory viral infections.

Objectives

To define the epidemiology and outcomes of non-influenza respiratory viral infections in hospitalized adults.

Patients/Methods

Data on all patients ≥18 years of age with a positive molecular respiratory viral assay who were hospitalized at a single tertiary healthcare system in Chicago, IL, from retrospectively collected and analyzed.

Results

Over the study period, 503 of 46 024 (1·1%) admitted patients had a positive RVP result. Human rhinovirus was the most commonly detected virus followed by influenza A, human metapneumovirus, respiratory syncytial virus, and parainfluenza virus, adenovirus, and influenza B, respectively. Infection in immunocompromised patients was associated with a higher rate of progression to pneumonia and death.

Conclusions

Non-influenza respiratory viral infections are commonly detected among adults admitted to the hospital and can cause serious illness. The data can inform the prioritization of research into novel antiviral therapies for these infections.     

Pandemic A/H1N1 influenza: Transmission of the first cases in Spain

Introduction

Pandemic A/H1N1 influenza emerged in Mexico at the end of March 2009. Since then, it is still important to provide evidences that contributed to the international spread of the virus and to ascertain the attack rate of this new strain of influenza among the first cases in Spain that led to identify the first transmission in Europe.

Methods

Three pandemic A/H1N1 influenza groups related to an overseas flight were studied: 71 student group, 94 remaining passengers, and 68 contacts of confirmed cases. The attack rate with their 95% confidence interval (CI) among the student group and contacts was calculated. On April 26th, when the first cases were notified, strong preventive measures were implemented among the student group and the contacts of the confirmed cases.

Results

On 27th April, the first pandemic A/H1N1 influenza cases confirmed in Spain were three students that came back from Mexico by airplane. A student generated the first native case in Spain and one of the first cases in Europe. Similar attack rates were found between the student group (14.1%; CI: 12.1–16.1) and their contacts (13.2%; CI: 4.4–22.0), but no cases among remaining passengers were detected, suggesting low transmission risk during air travel.

Conclusion

The first cases of pandemic A/H1N1 influenza in Spain were imported by airplane from Mexico. Preventive efforts to reduce the impact of the influenza influenced that primary and secondary rates were lower than first estimations by WHO.     

Community‐acquired respiratory viruses and co‐infection among patients of Ontario sentinel practices,April 2009 to February 2010

Please cite this paper as: Peci et al. (2012) Community‐acquired respiratory viruses and co‐infection among patients of Ontario Sentinel practices, April 2009 to February 2010. Influenza and Other Respiratory Viruses 7(4), 559–566. Background Respiratory viruses are known to cocirculate but this has not been described in detail during an influenza pandemic. Objectives To describe respiratory viruses, including co‐infection and associated attributes such as age, sex or comorbidity, in patients presenting with influenza‐like illness to a community sentinel network, during the pandemic A(H1N1)pdm09 in Ontario, Canada. Methods Respiratory samples and epidemiologic details were collected from 1018 patients with influenza‐like illness as part of respiratory virus surveillance and a multiprovincial case–control study of influenza vaccine effectiveness. Results At least one virus was detected in 668 (65·6%) of 1018 samples; 512 (50·3%) had single infections and 156 (15·3%) co‐infections. Of single infections, the most common viruses were influenza A in 304 (59·4%) samples of which 275 (90·5%) were influenza A(H1N1)pdm09, and enterovirus/rhinovirus in 149 (29·1%) samples. The most common co‐infections were influenza A and respiratory syncytial virus B, and influenza A and enterovirus/rhinovirus. In multinomial logistic regression analyses adjusted for age, sex, comorbidity, and timeliness of sample collection, single infection was less often detected in the elderly and co‐infection more often in patients <30 years of age. Co‐infection, but not single infection, was more likely detected in patients who had a sample collected within 2 days of symptom onset as compared to 3–7 days. Conclusions Respiratory viral co‐infections are commonly detected when using molecular techniques. Early sample collection increases likelihood of detection of co‐infection. Further studies are needed to better understand the clinical significance of viral co‐infection.     

Acute Respiratory Distress Syndrome as a presenting manifestation in young patients infected with H1N1 influenza virus

Introduction

The new strain of influenza A (H1N1) 2009, often referred to colloquially as “swine flu”, which was first detected in April 2009, raised to a pandemic of which the impact was not completely predictable. As reported, numerous cases with severe respiratory failure were also seen among young previously healthy people.

Patients

In the present study, we report eight cases of influenza A (H1N1) 2009 admitted to our medical intensive care with severe respiratory failure between November and December 2009 and in January 2011. All patients were older than 30 but younger than 50 years, had clinical and radiological evidence of an Acute Respiratory Distress Syndrome (ARDS) and needed invasive ventilatory support.

Results

Six of the eight patients had no relevant underlying disease; one had a pre-existing idiopathic lung fibrosis and another had a chronic obstructive pulmonary disease (COPD), an abuse of alcohol and an adiposities grade 3. Four patients needed an extracorporeal membrane oxygenation (ECMO) due to severe respiratory failure with global respiratory insufficiency that could not be treated by conservative ventilatory support. The one patient with a pre-existing lung fibrosis died shortly after lung transplantation despite use of an extracorporeal membrane oxygenation. One other patient died due to a subarachnoidal bleeding under the anticoagulatory regime during ECMO therapy. The adipose COPD-patient died due to septic shock with multiple organ failure without possibility for ECMO support.

Conclusions

The clinical course of severe cases of influenza A (H1N1) 2009-infection is markedly different from the disease pattern seen during epidemics of seasonal influenza. Most of the patients admitted to our intensive care unit due to influenza A (H1N1) 2009 associated ARDS were previously healthy young people.     

Distribution of influenza and other acute respiratory viruses during the first year after the 2009–2010 influenza pandemic in the English‐ and Dutch‐speaking Caribbean countries

Background

Limited specimen collection and testing for influenza occurred in the English and Dutch‐speaking Caribbean countries prior to the 2009/2010 influenza pandemic. Caribbean Epidemiology Centre (CAREC) member countries rapidly mobilized to collect specimens during the pandemic and a vast majority of confirmed cases during the pandemic period were influenza A(H1N1)pdm09.

Objectives

To describe the aetiology and distribution of acute respiratory illness (ARI) among laboratory confirmed cases during the first year after the 2009/2010 influenza pandemic in the English‐ and Dutch‐speaking Caribbean.

Results

In total, 774 specimens were tested and 394 (52.7%) cases had positive laboratory confirmation. Respiratory syncytial virus (RSV) (28.4%) and influenza A(H3N2) (23.1%) were most frequently detected. RSV activity peaked in July 2011 while influenza A(H3N2) peaked in October 2010. Influenza was responsible for illness in greater numbers in persons 15–64 years while RSV was seen in primarily in children <5 years and adults >65 years. Other agents confirmed include rhinovirus (12.9%), influenza B (10.9%) and influenza A(H1N1)pdm09 (9.4%).

Conclusions

RSV and influenza A(H3N2) were the most common viruses identified during the first year after the influenza A(H1N1)pdm09 pandemic. Influenza was detected every month with peak activity corresponding to that typically seen in North America (October to March). In order to determine the seasonality of influenza and RSV, laboratory data from subsequent years and increased specimen submission is needed.     

Modified vaccinia virus Ankara expressing the hemagglutinin of pandemic (H1N1) 2009 virus induces cross‐protective immunity against Eurasian ‘avian‐like’ H1N1 swine viruses in mice

Objectives

To examine cross-reactivity between hemagglutinin (HA) derived from A/California/7/09 (CA/09) virus and that derived from representative Eurasian “avian-like” (EA) H1N1 swine viruses isolated in Italy between 1999 and 2008 during virological surveillance in pigs.

Design

Modified vaccinia virus Ankara (MVA) expressing the HA gene of CA/09 virus (MVA-HA-CA/09) was used as a vaccine to investigate cross-protective immunity against H1N1 swine viruses in mice.

Sample

Two classical swine H1N1 (CS) viruses and four representative EA-like H1N1 swine viruses previously isolated during outbreaks of respiratory disease in pigs on farms in Northern Italy were used in this study.

Setting

Female C57BL/6 mice were vaccinated with MVA/HA/CA/09 and then challenged intranasally with H1N1 swine viruses.

Main outcome measures

Cross-reactive antibody responses were determined by hemagglutination- inhibition (HI) and virus microneutralizing (MN) assays of sera from MVA-vaccinated mice. The extent of protective immunity against infection with H1N1 swine viruses was determined by measuring lung viral load on days 2 and 4 post-challenge.

Results and Conclusions

Systemic immunization of mice with CA/09-derived HA, vectored by MVA, elicited cross-protective immunity against recent EA-like swine viruses. This immune protection was related to the levels of cross-reactive HI antibodies in the sera of the immunized mice and was dependent on the similarity of the antigenic site Sa of H1 HAs. Our findings suggest that the herd immunity elicited in humans by the pandemic (H1N1) 2009 virus could limit the transmission of recent EA-like swine HA genes into the influenza A virus gene pool in humans.     

Epidemiological and clinical features of respiratory viral infections in hospitalized children during the circulation of influenza virus A(H1N1) 2009

Please cite this paper as: Zuccotti et al. (2011) Epidemiological and clinical features of respiratory viral infections in hospitalized children during the circulation of influenza virus A(H1N1) 2009. Influenza and Other Respiratory Viruses 5(6), e528–e534. Background Seasonal influenza viruses and respiratory syncytial virus (RSV) are primary causes of acute respiratory tract infections (ARTIs) in children. New respiratory viruses including human metapneumovirus (hMPV), human bocavirus (hBoV), and influenza 2009 A(H1N1) virus have a strong impact on the pediatric population. Objectives To evaluate epidemiological and clinical features of ARTIs in hospitalized children. Methods From December 1, 2008, to December 31, 2009, all children under age fifteen (n = 575) hospitalized for ARTIs were investigated for influenza A (subtype H1N1, H3N2, and 2009 H1N1) and B, RSV A and B, hMPV, and hBoV by PCR. Results Fifty‐one percent of samples were positive for these respiratory viruses. The frequencies of virus detection were RSV 34·1%, hBoV 6·8%, hMPV 5%, seasonal influenza A 5%, and seasonal influenza B 0%. From April 2009, 11·6% of collected samples were influenza 2009 A(H1N1) positive. Respiratory syncytial virus activity peaked in January, hBoV in February, and hMPV in April. Seasonal influenza A was detected only between January and April 2009, while influenza 2009 A(H1N1) peaked in November. Respiratory syncytial virus and hMPV were mainly associated with lower respiratory tract infections (LRTIs) and with necessity of O₂ administration. The 2009 pandemic influenza was more frequently detected in elder children (P < 0·001) and was associated with higher, longer‐lasting fevers compared with other viral infections (P < 0·05). Conclusions All considered viruses were involved in LRTIs. The primary clinical relevance of RSV and a similar involvement of both seasonal influenza and emerging viruses investigated were observed on the pediatric population.     

Zoonotic Influenza and Human Health—Part 1: Virology and Epidemiology of Zoonotic Influenzas

Purpose of Review

Zoonotic influenza viruses are those that cross the animal-human barrier and can cause disease in humans, manifesting from minor respiratory illnesses to multiorgan dysfunction. They have also been implicated in the causation of deadly pandemics in recent history. The increasing incidence of infections caused by these viruses worldwide has necessitated focused attention to improve both diagnostic as well as treatment modalities. In this first part of a two-part review, we describe the structure of zoonotic influenza viruses, the relationship between mutation and pandemic capacity, pathogenesis of infection, and also discuss history and epidemiology.

Recent Findings

We are currently witnessing the fifth and the largest wave of the avian influenza A(H7N9) epidemic. Also in circulation are a number of other zoonotic influenza viruses, including avian influenza A(H5N1) and A(H5N6); avian influenza A(H7N2); and swine influenza A(H1N1)v, A(H1N2)v, and A(H3N2)v viruses. Most recently, the first human case of avian influenza A(H7N4) infection has been documented.

Summary

By understanding the virology and epidemiology of emerging zoonotic influenzas, we are better prepared to face a new pandemic. However, continued effort is warranted to build on this knowledge in order to efficiently combat the constant threat posed by the zoonotic influenza viruses.

     

Zoonotic Influenza and Human Health—Part 2: Clinical Features,Diagnosis, Treatment,and Prevention Strategies

Purpose of Review

Zoonotic influenza viruses are those influenza viruses that cross the animal-human barrier and can cause disease in humans, manifesting from minor respiratory illnesses to multiorgan dysfunction. The increasing incidence of infections caused by these viruses worldwide has necessitated focused attention to improve both diagnostic as well as treatment modalities. In this second part of a two-part review, we discuss the clinical features, diagnostic modalities, and treatment of zoonotic influenza, and provide an overview of prevention strategies.

Recent Findings

Illnesses caused by novel reassortant avian influenza viruses continue to be detected and described; most recently, a human case of avian influenza A(H7N4) has been described from China. We continue to witness increasing rates of A(H7N9) infections, with the latest (fifth) wave, from late 2016 to 2017, being the largest to date. The case fatality rate for A(H7N9) and A(H5N1) infections among humans is much higher than that of seasonal influenza infections. Since the emergence of the A(H1N1) 2009 pandemic, and subsequently A(H7N9), testing and surveillance for novel influenzas have become more effective. Various newer treatment options, including peramivir, favipiravir (T-705), and DAS181, and human or murine monoclonal antibodies have been evaluated in vitro and in animal models.

Summary

Armed with robust diagnostic modalities, antiviral medications, vaccines, and advanced surveillance systems, we are today better prepared to face a new influenza pandemic and to limit the burden of zoonotic influenza than ever before. Sustained efforts and robust research are necessary to efficiently deal with the highly mutagenic zoonotic influenza viruses.

     

Epidemiological and viral genome characteristics of the first human H7N9 influenza infection in Guangdong Province,China

Background

The first H7N9 human case in south of China was confirmed in Guangdong Province on August 2013, outside of the typical influenza season. For investigating the H7N9 virus source and transmission in the local community, we analyze the epidemiology and genome features of the virus isolated from the first human infection detected in Guangdong Province.

Methods

The data including medical records, exposure history and time line of events for the H7N9 patient and close contacts was collected. Variation and genetic signatures of H7N9 virus in Guangdong was analyzed using ClustalW algorithm and comparison with mutations associated with changes in biological characteristics of the virus.

Results

The female patient had a history of poultry exposure, and she was transferred from a local primary hospital to an intensive care unit (ICU) upon deterioration. No additional cases were reported. Similar to previous infections with avian influenza A (H7N9) virus, the patient presented with both upper and lower respiratory tract symptoms. Respiratory failure progressed quickly, and the patient recovered 4 weeks after the onset of symptoms. Genome analysis of the virus indicated that the predicted antigen city and internal genes of the virus are similar to previously reported H7N9 viruses. The isolated virus is susceptible to neuraminidase (NA) inhibitors but resistant to adamantine. Although this virus contains some unique mutations that were only detected in avian or environment-origin avian influenza A (H7N9) viruses, it is still quite similar to other human H7N9 isolates.

Conclusions

The epidemiological features and genome of the first H7N9 virus in Guangdong Province are similar to other human H7N9 infections. This virus may have existed in the environment and live poultry locally; therefore, it is important to be alert of the risk of H7N9 re-emergence in China, including emergence outside the typical influenza season.     

Prevalence,genetics, and transmissibility in ferrets of Eurasian avian-like H1N1 swine influenza viruses

Pigs are important intermediate hosts for generating novel influenza viruses. The Eurasian avian-like H1N1 (EAH1N1) swine influenza viruses (SIVs) have circulated in pigs since 1979, and human cases associated with EAH1N1 SIVs have been reported in several countries. However, the biologic properties of EAH1N1 SIVs are largely unknown. Here, we performed extensive influenza surveillance in pigs in China and isolated 228 influenza viruses from 36,417 pigs. We found that 139 of the 228 strains from pigs in 10 provinces in China belong to the EAH1N1 lineage. These viruses formed five genotypes, with two distinct antigenic groups, represented by A/swine/Guangxi/18/2011 and A/swine/Guangdong/104/2013, both of which are antigenically and genetically distinct from the current human H1N1 viruses. Importantly, the EAH1N1 SIVs preferentially bound to human-type receptors, and 9 of the 10 tested viruses transmitted in ferrets by respiratory droplet. We found that 3.6% of children (≤10 y old), 0% of adults, and 13.4% of elderly adults (≥60 y old) had neutralization antibodies (titers ≥40 in children and ≥80 in adults) against the EAH1N1 A/swine/Guangxi/18/2011 virus, but none of them had such neutralization antibodies against the EAH1N1 A/swine/Guangdong/104/2013 virus. Our study shows the potential of EAH1N1 SIVs to transmit efficiently in humans and suggests that immediate action is needed to prevent the efficient transmission of EAH1N1 SIVs to humans.Pigs play a pivotal role in the ecology of influenza A viruses, being regarded as intermediate hosts for the generation of novel and potentially dangerous influenza viruses for humans. Cellular receptors containing α-2,3–linked sialic acids (Sias) (avian-like receptors) and α-2,6–linked Sias (human-like receptors) in the pig trachea favor the productive replication of viruses from both the avian and mammalian lineages (1). Influenza viruses of the subtypes H1N1, H1N2, and H3N2 are circulating in pigs globally (2). Two lineages of H1N1 swine influenza viruses (SIVs), classical H1N1 SIVs and Eurasian avian-like H1N1 (EAH1N1) SIVs, have been circulating in pigs since 1918 and 1979, respectively (3, 4). The classical H1N1 SIVs emerged in humans as a reassortant (2009/H1N1) and caused the 2009 H1N1 influenza pandemic (5). The EAH1N1 SIVs have been detected in pigs in many Eurasian countries (6) and have caused several human infections in European countries and also in China (7–11), where a fatal case was reported (11). EAH1N1 SIVs are reported to be most prevalent in pigs that have been brought into Hong Kong since 2005 (12). However, the evolution and biologic properties of the EAH1N1 SIVs are largely unknown.China is the largest pork-producing country in the world. Pigs in China are not vaccinated against influenza, and therefore, influenza viruses can spread freely once they are introduced into pig herds. In this study, we performed active surveillance in pigs and found that the EAH1N1 SIVs are predominant in the pig population in China; we further found that the EAH1N1 SIVs pose an imminent threat with regard to their ability to cause a human influenza pandemic.     

Early occurrence of influenza A epidemics coincided with changes in occurrence of other respiratory virus infections

Background

Viral interaction in which outbreaks of influenza and other common respiratory viruses might affect each other has been postulated by several short studies. Regarding longer time periods, influenza epidemics occasionally occur very early in the season, as during the 2009 pandemic. Whether early occurrence of influenza epidemics impacts outbreaks of other common seasonal viruses is not clear.

Objectives

We investigated whether early occurrence of influenza outbreaks coincides with shifts in the occurrence of other common viruses, including both respiratory and non‐respiratory viruses.

Methods

We investigated time trends of and the correlation between positive laboratory diagnoses of eight common viruses in the Netherlands over a 10‐year time period (2003–2012): influenza viruses types A and B, respiratory syncytial virus (RSV), rhinovirus, coronavirus, norovirus, enterovirus, and rotavirus. We compared trends in viruses between early and late influenza seasons.

Results

Between 2003 and 2012, influenza B, RSV, and coronavirus showed shifts in their occurrence when influenza A epidemics occurred earlier than usual (before week 1). Although shifts were not always consistently of the same type, when influenza type A hit early, RSV outbreaks tended to be delayed, coronavirus outbreaks tended to be intensified, and influenza virus type B tended not to occur at all. Occurrence of rhinovirus, norovirus, rotavirus, and enterovirus did not change.

Conclusion

When influenza A epidemics occured early, timing of the epidemics of several respiratory winter viruses usually occurring close in time to influenza A was affected, while trends in rhinoviruses (occurring in autumn) and trends in enteral viruses were not.     

Distribution of antibodies against influenza virus in pigs from farrow‐to‐finish farms in Minas Gerais state,Brazil

Background

Swine influenza virus (SIV) is the cause of an acute respiratory disease that affects swine worldwide. In Brazil, SIV has been identified in pigs since 1978. After the emergence of pandemic H1N1 in 2009 (H1N1pdm09), few studies reported the presence of influenza virus in Brazilian herds.

Objectives

The objective of this study was to evaluate the serological profile for influenza virus in farrow-to-finish pig farms in Minas Gerais state, Brazil.

Methods

Thirty farms with no SIV vaccination history were selected from the four larger pig production areas in Minas Gerais state (Zona da Mata, Triângulo Mineiro/Alto Paranaíba, South/Southwest and the Belo Horizonte metropolitan area). At each farm, blood samples were randomly collected from 20 animals in each production cycle category: breeding animals (sows and gilts), farrowing crate (2–3 weeks), nursery (4–7 weeks), grower pigs (8–14 weeks), and finishing pigs (15–16 weeks), with 100 samples per farm and a total of 3000 animals in this study. The samples were tested for hemagglutination inhibition activity against H1N1 pandemic strain (A/swine/Brazil/11/2009) and H3N2 SIV (A/swine/Iowa/8548-2/98) reference strain.

Results

The percentages of seropositive animals for H1N1pdm09 and H3N2 were 26·23% and 1·57%, respectively, and the percentages of seropositive herds for both viruses were 96·6% and 13·2%, respectively.

Conclusions

The serological profiles differed for both viruses and among the studied areas, suggesting a high variety of virus circulation around the state, as well as the presence of seronegative animals susceptible to influenza infection and, consequently, new respiratory disease outbreaks.     

Characterizing wild bird contact and seropositivity to highly pathogenic avian influenza A (H5N1) virus in Alaskan residents

Background

Highly pathogenic avian influenza A (HPAI) H5N1 viruses have infected poultry and wild birds on three continents with more than 600 reported human cases (59% mortality) since 2003. Wild aquatic birds are the natural reservoir for avian influenza A viruses, and migratory birds have been documented with HPAI H5N1 virus infection. Since 2005, clade 2.2 HPAI H5N1 viruses have spread from Asia to many countries.

Objectives

We conducted a cross-sectional seroepidemiological survey in Anchorage and western Alaska to identify possible behaviors associated with migratory bird exposure and measure seropositivity to HPAI H5N1.

Methods

We enrolled rural subsistence bird hunters and their families, urban sport hunters, wildlife biologists, and a comparison group without bird contact. We interviewed participants regarding their exposures to wild birds and collected blood to perform serologic testing for antibodies against a clade 2.2 HPAI H5N1 virus strain.

Results

Hunters and wildlife biologists reported exposures to wild migratory birds that may confer risk of infection with avian influenza A viruses, although none of the 916 participants had evidence of seropositivity to HPAI H5N1.

Conclusions

We characterized wild bird contact among Alaskans and behaviors that may influence risk of infection with avian influenza A viruses. Such knowledge can inform surveillance and risk communication surrounding HPAI H5N1 and other influenza viruses in a population with exposure to wild birds at a crossroads of intercontinental migratory flyways.