Protective measures and human antibody response during an avian influenza H7N3 outbreak in poultry in British Columbia, Canada

The Alarming Situation of Highly Pathogenic Avian Influenza Viruses in 2019-2023

Avian influenza viruses (AIVs) have the potential to cause severe illness in wild birds, domestic poultry, and humans. The ongoing circulation of highly pathogenic avian influenza viruses (HPAIVs) has presented significant challenges to global poultry industry and public health in recent years. This study aimed to elucidate the circulation of HPAIVs during 2019 to 2023. Specifically, we assess the alarming global spread and continuous evolution of HPAIVs. Moreover, we discuss their transmission and prevention strategies to provide valuable references for future prevention and control measures against AIVs.

Safety and immunogenicity of an alum-adjuvanted whole-virion H7N9 influenza vaccine: a randomized, blinded, clinical trial

OBJECTIVES

A case of H7N9 influenza virus infection was first identified in China in 2013. This virus is considered to have high pandemic potential. Here we developed an H7N9 influenza vaccine containing an aluminium adjuvant and evaluated the safety and immunogenicity of the vaccine.

METHODS

From October 2017 through August 2018 we conducted a randomized, double-blinded, single-centre phase I clinical trial in China among 360 participants aged ≥12 years. All participants received two doses of the vaccine (7.5, 15 or 30 μg haemagglutinin antigen) or placebo at an interval of 21 days. Adverse event data were collected for 30 days after vaccination. Serum samples were collected on days 0, 21 and 42 for the haemagglutinin inhibition (HI) antibody assay.

RESULTS

A total of 347 participants (347/360, 96.4%) completed the study. The proportions of vaccine-related adverse events after one injection were 56.7% (34/60) in the 7.5-μg group, 86.7% (52/60) in the 15-μg group and 86.7% (52/60) in the 30-μg group. The proportions of adverse events after two injections were less than those reported after the first dose. None of the serious adverse events were related to the vaccine. After receiving two doses of the 7.5-μg vaccine, the proportion of participants achieving an HI titre of ≥40 was 98.2% (55/56, 95%CI 72.3~100.0%), with a geometric mean titre (GMT) of 192.6 (95%CI 162.9~227.8).

CONCLUSIONS

The alum-adjuvanted H7N9 whole-virion inactivated vaccine was safe and strongly immunogenic in a population aged ≥12 years.

Specific memory B cell response in humans upon infection with highly pathogenic H7N7 avian influenza virus

H7 avian influenza viruses represent a major public health concern, and worldwide outbreaks raise the risk of a potential pandemic. Understanding the memory B cell response to avian (H7) influenza virus infection in humans could provide insights in the potential key to human infection risks. We investigated an epizootic of the highly pathogenic A(H7N7) in the Netherlands, which in 2003 led to infection of 89 persons and one fatal case. Subtype-specificity of antibodies were determined for confirmed H7N7 infected individuals (cases) (n = 19), contacts of these cases (n = 21) and a comparison group controls (n = 16), by microarray, using recombinant hemagglutinin (HA)1 proteins. The frequency and specificity of memory B cells was determined by detecting subtype-specific antibodies in the culture supernatants from in vitro stimulated oligoclonal B cell cultures, from peripheral blood of cases and controls. All cases (100%) had high antibody titers specific for A(H7N7)2003 (GMT > 100), whereas H7-HA1 antigen binding was detected in 29% of contacts and 31% of controls, suggesting that some of the H7 reactivity stems from cross reactive antibodies. To unravel homotypic and heterotypic responses, the frequency and specificity of memory B cells were determined in 2 cases. Ten of 123 HA1 reactive clones isolated from the cases bound to only H7- HA1, whereas 5 bound both H7 and other HA1 antigens. We recovered at least four different epitopal reactivities, though none of the H7 reactive antibodies were able to neutralize H7 infections in vitro. Our study serologically confirms the infection with H7 avian influenza viruses, and shows that H7 infection triggers a mixture of strain -specific and cross-reactive antibodies.

NEUTRALIZING ANTIBODIES TO TYPE A INFLUENZA VIRUSES IN SHOREBIRDS AT DELAWARE BAY, NEW JERSEY, USA

Influenza A virus (IAV) infections in shorebirds at Delaware Bay, New Jersey, US, have historically included avian hemagglutinin (HA) subtypes H1-13 and H16. In a given year, infections are characterized by a limited number of HA and neuraminidase subtypes and a dominant HA subtype that often represents >50% of all isolates. Predominant HA subtypes shift between consecutive years. In addition, infection prevalence is consistently higher in Ruddy Turnstones (RUTU; Arenaria interpres morinella) compared to Red Knots (REKN; Calidris canutus rufa), despite comparable rates of exposure. To investigate a potential immunological basis for this phenomenon, a virus microneutralization assay was used to detect subtype-specific, neutralizing antibodies to H1-H12 in sera collected from RUTUs from 2012-16 and REKNs in 2012, 2013, and 2016. Neutralizing antibodies to one or more subtypes were detected in 36% (222/611) of RUTUs. Prevalence of antibodies to subtypes H6 and H11 remained high throughout the study, and these virus subtypes were isolated every year, suggesting a continual source of exposure. Antibody prevalence was intermediate for most IAV subtypes that were isolated in 2-3 of 5 yr (H1, H3, H5, H9, H10, and H12) but was low for H7 viruses, despite the isolation of this virus subtype in 3 of 5 yr. This suggests a reduced antigenicity of H7 IAVs compared to other subtypes. Antibody prevalence was low for H4 virus that was isolated once, and H2 and H8 viruses that were never isolated. Neutralizing antibodies were detected in 66% (169/257) of REKNs and subtype-specific antibody prevalences were higher in REKNs than RUTUs with few exceptions. The results suggest that population immunity influences which species is infected at Delaware Bay, indicate that IAV dynamics are subtype-dependent, and demonstrate the utility of the microneutralization assay as a supportive tool for field research.

The eyes have it: influenza virus infection beyond the respiratory tract

Avian and human influenza A viruses alike have shown a capacity to use the eye as a portal of entry and cause ocular disease in human beings. However, whereas influenza viruses generally represent a respiratory pathogen and only occasionally cause ocular complications, the H7 virus subtype stands alone in possessing an ocular tropism. Clarifying what confers such non-respiratory tropism to a respiratory virus will permit a greater ability to identify, treat, and prevent zoonotic human infection following ocular exposure to influenza viruses; especially those within the H7 subtype, which continue to cause avian epidemics on many continents.

Low risk of avian influenza A (H5N6) transmission to depopulation workers in Korea

An outbreak of highly pathogenic avian influenza A (H5N6) virus occurred between November 20, 2016, and March 1, 2017 in poultry farms, in the Gyeonggi Province, Republic of Korea. To identify the risk of transmission of H5N6 to depopulation workers, active and passive surveillance was conducted. Virological testing of respiratory swabs with real‐time reverse transcription‐polymerase chain reaction was performed for workers who reported respiratory symptoms. Among 4633 depopulation workers, 22 reported respiratory symptoms, but all tested negative for H5N6. Personal protective equipment in addition to antiviral prophylaxis was adequate to limit transmission of H5N6 from poultry to humans.

Inactivated H7 Influenza Virus Vaccines Protect Mice despite Inducing Only Low Levels of Neutralizing Antibodies

Avian influenza viruses of the H7 hemagglutinin (HA) subtype present a significant public health threat, as evidenced by the ongoing outbreak of human A(H7N9) infections in China. When evaluated by hemagglutination inhibition (HI) and microneutralization (MN) assays, H7 viruses and vaccines are found to induce lower level of neutralizing antibodies (nAb) than do their seasonal counterparts, making it difficult to develop and evaluate prepandemic vaccines. We have previously shown that purified recombinant H7 HA appear to be poorly immunogenic in that they induce low levels of HI and MN antibodies. In this study, we immunized mice with whole inactivated reverse genetics reassortant (RG) viruses expressing HA and neuraminidase (NA) from 3 different H7 viruses [A/Shanghai/2/2013(H7N9), A/Netherlands/219/2003(H7N7), and A/New York/107/2003(H7N2)] or with human A(H1N1)pdm09 (A/California/07/2009-like) or A(H3N2) (A/Perth16/2009) viruses. Mice produced equivalent titers of antibodies to all viruses as measured by enzyme-linked immunosorbent assay (ELISA). However, the antibody titers induced by H7 viruses were significantly lower when measured by HI and MN assays. Despite inducing very low levels of nAb, H7 vaccines conferred complete protection against homologous virus challenge in mice, and the serum antibodies directed against the HA head region were capable of mediating protection. The apparently low immunogenicity associated with H7 viruses and vaccines may be at least partly related to measuring antibody titers with the traditional HI and MN assays, which may not provide a true measure of protective immunity associated with H7 immunization. This study underscores the need for development of additional correlates of protection for prepandemic vaccines.IMPORTANCE H7 avian influenza viruses present a serious risk to human health. Preparedness efforts include development of prepandemic vaccines. For seasonal influenza viruses, protection is correlated with antibody titers measured by hemagglutination inhibition (HI) and virus microneutralization (MN) assays. Since H7 vaccines typically induce low titers in HI and MN assays, they have been considered to be poorly immunogenic. We show that in mice H7 whole inactivated virus vaccines (WIVs) were as immunogenic as seasonal WIVs, as they induced similar levels of overall serum antibodies. However, a larger fraction of the antibodies induced by H7 WIV was nonneutralizing in vitro Nevertheless, the H7 WIV completely protected mice against homologous viral challenge, and antibodies directed against the HA head were the major contributor toward immune protection. Vaccines against H7 avian influenza viruses may be more effective than HI and virus neutralization assays suggest, and such vaccines may need other methods for evaluation.

Review of Nonfoodborne Zoonotic and Potentially Zoonotic Poultry Diseases

Emerging and re-emerging diseases are continuously diagnosed in poultry species. A few of these diseases are known to cross the species barrier, thus posing a public health risk and an economic burden. We identified and synthesized global evidence for poultry nonfoodborne zoonoses to better understand these diseases in people who were exposed to different poultry-related characteristics (e.g., occupational or nonoccupational, operational types, poultry species, outbreak conditions, health status of flocks). This review builds on current knowledge on poultry zoonoses/potentially zoonotic agents transmitted via the nonfoodborne route. It also identifies research gaps and potential intervention points within the poultry industry to reduce zoonotic transmission by using various knowledge synthesis tools such as systematic review (SR) and qualitative (descriptive) and quantitative synthesis methods (i.e., meta-analysis). Overall, 1663 abstracts were screened and 156 relevant articles were selected for further review. Full articles (in English) were retrieved and critically appraised using routine SR methods. In total, eight known zoonotic diseases were reviewed: avian influenza (AI) virus (n = 85 articles), Newcastle disease virus (n = 8), West Nile virus (WNV, n = 2), avian Chlamydia (n = 24), Erysipelothrix rhusiopathiae (n = 3), methicillin-resistant Staphylococcus aureus (MRSA, n = 15), Ornithonyssus sylvarium (n = 4), and Microsporum gallinae (n = 3). In addition, articles on other viral poultry pathogens (n = 5) and poultry respiratory allergens derived from mites and fungi (n = 7) were reviewed. The level of investigations (e.g., exposure history, risk factor, clinical disease in epidemiologically linked poultry, molecular studies) to establish zoonotic linkages varied across disease agents and across studies. Based on the multiple outcome measures captured in this review, AI virus seems to be the poultry zoonotic pathogen that may have considerable and significant public health consequences; however, epidemiologic reports have only documented severe human cases clustered in Asia and not in North America. In contrast, avian Chlamydia and MRSA reports clustered mainly in Europe and less so in North America and other regions. Knowledge gaps in other zoonoses or other agents were identified, including potential direct (i.e., nonmosquito-borne) transmission of WNV from flocks to poultry workers, the public health and clinical significance of poultry-derived (livestock-associated) MRSA, the zoonotic significance of other viruses, and the role of poultry allergens in the pathophysiology of respiratory diseases of poultry workers. Across all pathogens reviewed, the use of personal protective equipment was commonly cited as the most important preventive measure to reduce the zoonotic spread of these diseases and the use of biosecurity measures to reduce horizontal transmission in flock populations. The studies also emphasized the need for flock monitoring and an integrated approach to prevention (i.e., veterinary-public health coordination with regard to diagnosis, and knowledge translation and education in the general population) to reduce zoonotic transmission.

Induction of Broadly Cross-Reactive Stalk-Specific Antibody Responses to Influenza Group 1 and Group 2 Hemagglutinins by Natural H7N9 Virus Infection in Humans

Background

The outbreak of novel avian H7N9 influenza virus infections in China in 2013 has demonstrated the continuing threat posed by zoonotic pathogens. Deciphering the immune response during natural infection will guide future vaccine development.

Methods

We assessed the induction of heterosubtypic cross-reactive antibodies induced by H7N9 infection against a large panel of recombinant hemagglutinins and neuraminidases by quantitative enzyme-linked immunosorbent assay, and novel chimeric hemagglutinin constructs were used to dissect the anti-stalk or -head humoral immune response.

Results

H7N9 infection induced strong antibody responses against divergent H7 hemagglutinins. Interestingly, we also found induction of antibodies against heterosubtypic hemagglutinins from both group 1 and group 2 and a boost in heterosubtypic neutralizing activity in the absence of hemagglutination inhibitory activity. Kinetic monitoring revealed that heterosubtypic binding/neutralizing antibody responses typically appeared and peaked earlier than intrasubtypic responses, likely mediated by memory recall responses.

Conclusions

Our results indicate that cross-group binding and neutralizing antibody responses primarily targeting the stalk region can be elicited after natural influenza virus infection. These data support our understanding of the breadth of the postinfection immune response that could inform the design of future, broadly protective influenza virus vaccines.

Weighing serological evidence of human exposure to animal influenza viruses - a literature review

Assessing influenza A virus strains circulating in animals and their potential to cross the species barrier and cause human infections is important to improve human influenza surveillance and preparedness. We reviewed studies describing serological evidence of human exposure to animal influenza viruses. Comparing serological data is difficult due to a lack of standardisation in study designs and in laboratory methods used in published reports. Therefore, we designed a scoring system to assess and weigh specificity of obtained serology results in the selected articles. Many studies report reliable evidence of antibodies to swine influenza viruses among persons occupationally exposed to pigs. Most avian influenza studies target H5, H7 and H9 subtypes and most serological evidence of human exposure to avian influenza viruses is reported for these subtypes. Avian influenza studies receiving a low grade in this review often reported higher seroprevalences in humans compared with studies with a high grade. Official surveillance systems mainly focus on avian H5 and H7 viruses. Swine influenza viruses and avian subtypes other than H5 and H7 (emphasising H9) should be additionally included in official surveillance systems. Surveillance efforts should also be directed towards understudied geographical areas, such as Africa and South America.

Human-livestock contacts and their relationship to transmission of zoonotic pathogens, a systematic review of literature

BACKGROUND

Micro-organisms transmitted from vertebrate animals - including livestock - to humans account for an estimated 60% of human pathogens. Micro-organisms can be transmitted through inhalation, ingestion, via conjunctiva or physical contact. Close contact with animals is crucial for transmission. The role of intensity and type of contact patterns between livestock and humans for disease transmission is poorly understood. In this systematic review we aimed to summarise current knowledge regarding patterns of human-livestock contacts and their role in micro-organism transmission.

METHODS

We included peer-reviewed publications published between 1996 and 2014 in our systematic review if they reported on human-livestock contacts, human cases of livestock-related zoonotic diseases or serological epidemiology of zoonotic diseases in human samples. We extracted any information pertaining the type and intensity of human-livestock contacts and associated zoonoses.

RESULTS

1522 papers were identified, 75 were included: 7 reported on incidental zoonoses after brief animal-human contacts (e.g. farm visits), 10 on environmental exposures and 15 on zoonoses in developing countries where backyard livestock keeping is still customary. 43 studies reported zoonotic risks in different occupations. Occupations at risk included veterinarians, culling personnel, slaughterhouse workers and farmers. For culling personnel, more hours exposed to livestock resulted in more frequent occurrence of transmission. Slaughterhouse workers in contact with live animals were more often positive for zoonotic micro-organisms compared to co-workers only exposed to carcasses. Overall, little information was available about the actual mode of micro-organism transmission.

CONCLUSIONS

Little is known about the intensity and type of contact patterns between livestock and humans that result in micro-organism transmission. Studies performed in occupational settings provide some, but limited evidence of exposure response-like relationships for livestock-human contact and micro-organism transmission. Better understanding of contact patterns driving micro-organism transmission from animals to humans is needed to provide options for prevention and thus deserves more attention.

Avian Influenza A(H7N9) Virus Infection in 2 Travelers Returning from China to Canada, January 2015

In January 2015, British Columbia, Canada, reported avian influenza A(H7N9) virus infection in 2 travelers returning from China who sought outpatient care for typical influenza-like illness. There was no further spread, but serosurvey findings showed broad population susceptibility to H7N9 virus. Travel history and timely notification are critical to emerging pathogen detection and response.

A systematic review of factors affecting intended and actual adherence with antiviral medication as treatment or prophylaxis in seasonal and pandemic flu

The aim of this review was to identify factors predicting actual or intended adherence to antivirals as treatment or prophylaxis for influenza. Literature from inception to March 2015 was systematically reviewed to find studies reporting predictors of adherence to antivirals and self‐reported reasons for non‐adherence to antivirals. Twenty‐six studies were included in the review; twenty identified through the literature search and six through other means. Of these studies, 18 assessed predictors of actual adherence to antivirals, whereas eight assessed predictors of intended adherence. The most commonly found predictor of, and self‐reported reason for, non‐adherence was the occurrence of side effects. Other predictors include perceptions surrounding self‐efficacy, response efficacy and perceived personal consequences as well as social influences of others' experiences of taking antivirals. Predictors identified in this review can be used to help inform communications to increase adherence to antivirals in both seasonal and pandemic influenza.

Public health response to outbreaks of Avian Influenza A(H5N2) and (H5N1) among poultry - British Columbia, December 2014-February 2015

In December 2014, the first detection in Canada of a highly pathogenic avian influenza A (HPAI) virus was reported in poultry within the Fraser Health Authority of British Columbia. It was the second outbreak of HPAI from Eurasian H5 reassortment viruses in North America. The Fraser Health Authority provided the lead public health coordination for this response as well as consultation and support to the occupational health response. The public health response focused on contact tracing, monitoring and follow-up for household, farm worker and other community contacts exposed on the affected farms. A total of 50 contacts were identified. Contacts received daily active monitoring by public health nurses for seven days from their last exposure and were advised to self-monitor until day 10. All contacts and other household members were recommended seasonal influenza vaccination to protect against further possible reassortment with human influenza viruses circulating within the community at the time. A total of 26 (52%) contacts were recommended chemoprophylaxis for ongoing exposure to the affected barns and flocks, of whom only 11 (42%) initiated this. During the seven-day active surveillance period, four contacts developed acute respiratory symptoms and influenza B was identified in one individual. Local area health care providers and acute care facilities were alerted to the outbreak and public messaging was provided regarding the human health risks from avian influenza. Collaboration between health and agriculture at the local, regional, provincial and federal levels was key to a rapid response to this outbreak.

Emerging Influenza Strains in the Last Two Decades: A Threat of a New Pandemic?

In the last 20 years, novel non-seasonal influenza viruses have emerged, most of which have originated from birds. Despite their apparent inability to cause pandemics, with the exception of H1N1 swine influenza virus, these viruses still constitute a constant threat to public health. While general concern has decreased after the peak of the H5N1 virus, in recent years several novel reassorted influenza viruses (e.g., H7N9, H9N2, H10N8) have jumped the host-species barrier and are under surveillance by the scientific community and public health systems. It is still unclear whether these viruses can actually cause pandemics or just isolated episodes. The purpose of this review is to provide an overview of old and novel potential pandemic strains of recent decades.

Personal Protective Equipment Use and Handwashing Among Animal Farmers: A Multi-site Assessment

The goal of this study was to compare and contrast the use of personal protective equipment (PPE) and the practice of handwashing among participants of four studies assessing poultry and swine farms in the midwestern United States and in Thailand. This largely descriptive exercise was designed to assess and compare the frequency of these protective practices among the study populations. There were a total of 1113 surveys analyzed across the four studies. The respondents included workers in direct contact with animals as well as flock owners and veterinarians tending to farms. Handwashing was the most common practice observed among all participants with 42% "always" and 35% "sometimes" washing their hands after contact with the animals. This practice was least common among Minnesota swine workers. Even Thai poultry farmers, who demonstrated the lowest overall PPE use, reported a higher frequency of handwashing. Mask use during animal farming activities ("always" or "sometimes") was least commonly practiced, ranging from 1% in Thailand to 26% among backyard poultry farmers in Minnesota. Minnesota poultry and swine farmers had similar frequencies of mask (26%) and glove use (51% and 49%). All other comparisons differed significantly across the four sites (p-values <0.05). The use of PPE in animal farming differed by study location and is likely related to prevalent norms in the respective regions. Overall, the use of PPE did not appear to be influenced by the particular animal (poultry or swine) being farmed. These findings may prove useful to regulating bodies and farm owners in formulating policy or planning strategies for improving personal hygiene practices in animal farming and preparing for influenza and other potential zoonotic disease outbreaks.

Recombinant influenza H7 hemagglutinins induce lower neutralizing antibody titers in mice than do seasonal hemagglutinins

Background

Vaccines against avian influenza viruses often require high hemagglutinin (HA) doses or adjuvants to achieve serological titers associated with protection against disease. In particular, viruses of the H7 subtype frequently do not induce strong antibody responses following immunization.

Objectives

To evaluate whether poor immunogenicity of H7 viruses is an intrinsic property of the H7 hemagglutinin.

Methods

We compared the immunogenicity, in naïve mice, of purified recombinant HA from two H7 viruses [A/Netherlands/219/2003(H7N7) and A/New York/107/2003(H7N2)] to that of HA from human pandemic [A/California/07/2009(H1N1pdm09)] and seasonal [A/Perth16/2009(H3N2)] viruses.

Results

After two intramuscular injections with purified hemagglutinin, mice produced antibodies to all HAs, but the response to the human virus HAs was greater than to H7 HAs. The difference was relatively minor when measured by ELISA, greater when measured by hemagglutination inhibition assays, and more marked still by microneutralization assays. H7 HAs induced little or no neutralizing antibody response in mice at either dose tested. Antibodies induced by H7 were of significantly lower avidity than for H3 or H1N1pdm09.

Conclusions

We conclude that H7 HAs may be intrinsically less immunogenic than HA from seasonal human influenza viruses.

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.

Relationship between domestic and wild birds in live poultry market and a novel human H7N9 virus in China

To trace the source of the avian H7N9 viruses, we collected 99 samples from 4 live poultry markets and the family farms of 3 patients in Hangzhou city of Zhejiang province, China. We found that almost all positive samples came from chickens and ducks in live poultry markets. These results strongly suggest that the live poultry markets are the major source of recent human infections with H7N9 in Hangzhou city, Zhejiang province of China. Therefore, control measures are needed, not only in the domestic bird population, but also in the live poultry markets to reduce human H7N9 infection risk.

Induction of cross-reactive antibodies to novel H7N9 influenza virus by recombinant Newcastle disease virus expressing a North American lineage H7 subtype hemagglutinin

Severe human disease caused by the emerging H7N9 influenza virus in China warrants a rapid response. Here, we present a recombinant Newcastle disease virus expressing a North American lineage H7 influenza virus hemagglutinin. Sera from immunized mice were cross-reactive to a broad range of H7 subtype viruses and inhibited hemagglutination by the novel H7 hemagglutinin. Immunized mice were protected against a heterologous H7 subtype challenge, and genetic analysis suggested that cross-protective antibodies recognize conserved antigenic sites.

Behind the mask: Determinants of nurse's adherence to facial protective equipment

BACKGROUND

As the predominant occupation in the health sector and as the health worker with the most patient interaction, nurses are at high risk for occupational transmission of communicable respiratory illness. The use of facial protective equipment (FPE) is an important strategy to prevent occupational transmission.

METHODS

A 2-phased study was conducted to examine nurse's adherence to recommended use of FPE. Phase 1 was a cross-sectional survey of nurses in selected units of 6 acute care hospitals in Toronto, Canada. Phase 2 was a direct observational study of critical care nurses.

RESULTS

Of the 1,074 nurses who completed surveys (82% response rate), 44% reported adherence to recommended use of FPE. Multivariable analysis revealed 6 predictors of adherence: unit type, frequency of equipment use, equipment availability, training, organizational support, and communication. Following the survey, 100 observations in 14 intensive care units were conducted that revealed a 44% competence rate with proper use of N95 respirators and knowledge as a significant predictor of competence.

CONCLUSION

Whereas increasing knowledge should enhance competence, strategies to improve adherence to recommended use of FPE in a busy and complex health care setting should focus on ready availability of equipment, training and fit testing, organizational support for worker health and safety, and good communication practices.

Use of personal protective measures by Thai households in areas with avian influenza outbreaks

Thailand has had multiple poultry outbreaks of highly pathogenic avian influenza (HPAI) H5N1 since its first emergence in 2004. Twenty-five human cases of HPAI H5N1 avian influenza have been reported in the country, including 17 fatalities, and contact with infected dead or dying poultry has been identified as a risk factor for human infection. This study assessed the use of protective equipment and hand hygiene measures by Thai poultry-owning households during activities involving poultry contact. Surveys conducted in 2008 included questions regarding poultry-related activities and protective measures used during an HPAI outbreak (2005) and 3 years after the study location's last reported outbreak (2008). For both time periods, poultry owners reported limited use of personal protective equipment (PPE) during all activities and inconsistent hand washing practices after carrying poultry and gathering eggs. This is the first time that PPE use in Thailand has been quantified for a large study group. These data are important for ongoing characterization of HPAI risk and for the crafting of educational messages.

Oseltamivir inhibits H7 influenza virus replication in mice inoculated by the ocular route

The majority of human infections associated with H7 influenza viruses have resulted in ocular and not respiratory disease. While oseltamivir has been prescribed to individuals presenting with conjunctivitis following H7 virus exposure, it is unknown if oseltamivir inhibits virus replication in ocular tissue. We demonstrate that H7 viruses possess sensitivity to neuraminidase inhibitors and that administration of oseltamivir before ocular virus challenge in mice inhibits H7N7 and H7N3 virus replication in ocular and respiratory tissues.

Effectiveness of personal protective equipment and oseltamivir prophylaxis during avian influenza A (H7N7) epidemic, the Netherlands, 2003

We analyzed the effectiveness of personal protective equipment and oseltamivir use during the 2003 avian influenza A (H7N7) epidemic in the Netherlands by linking databases containing information about farm visits, human infections, and use of oseltamivir and personal protective equipment. Using a stringent case definition, based on self-reported conjunctivitis combined with a positive hemagglutination-inhibition assay, we found that prophylactic treatment with oseltamivir significantly reduced the risk for infection per farm visit from 0.145 (95% confidence interval [CI] 0.078-0.233) to 0.031 (95% CI 0.008-0.073). The protective effect was ≈79% (95% CI 40%-97%). These results are comparable with the reported effect of prophylactic treatment with oseltamivir on human seasonal influenza. No significant protective effect was found for use of respirators or safety glasses, possibly because of limitations of the data.

Oseltamivir in human avian influenza infection

Avian influenza A viruses continue to cause disease outbreaks in humans, and extrapulmonary infection is characteristic. In vitro studies demonstrate the activity of oseltamivir against avian viruses of the H5, H7 and H9 subtypes. In animal models of lethal infection, oseltamivir treatment and prophylaxis limit viral replication and improve survival. Outcomes are influenced by the virulence of the viral strain, dosage regimen and treatment delay; it is also critical for the compound to act systemically. Observational data on oseltamivir treatment in the early stages of disease suggest it is useful for improving survival in patients infected with H5 viruses, and drug-selected resistance has only rarely been reported. The WHO strongly recommends oseltamivir for the treatment of confirmed or suspected cases of human H5 infection and prophylaxis of those at high risk of infection. In addition to oral dosing, nasogastric administration appears to be a viable option for the management of severely ill patients, as is the use of higher doses and prolonged schedules. F. Hoffmann-La Roche Ltd, the manufacturer of oseltamivir, is developing a mathematical model to allow rapid prediction of appropriate dosage regimens for any future pandemic. Roche is also funding the Avian Influenza Registry, an online database that aims to collect information from clinicians worldwide on the course of avian influenza in humans.

Protective measures and H5N1-seroprevalence among personnel tasked with bird collection during an outbreak of avian influenza A/H5N1 in wild birds, Ruegen, Germany, 2006

Background

In Germany, the first outbreak of highly pathogenic avian influenza A/H5N1 occurred among wild birds on the island of Ruegen between February and April 2006. The aim of this study was to investigate the use of recommended protective measures and to measure H5N1-seroprevalence among personnel tasked with bird collection.

Methods

Inclusion criteria of our study were participation in collecting wild birds on Ruegen between February and March 2006. Study participants were asked to complete a questionnaire, and to provide blood samples. For evaluation of the use of protective measures, we developed a personal protective equipment (PPE)-score ranging between 0 and 9, where 9 corresponds to a consistent and complete use of PPE. Sera were tested by plaque neutralization (PN) and microneutralization (MN) assays. Reactive sera were reanalysed in the World Health Organization-Collaborating Centre (WHO-CC) using MN assay.

Results

Of the eligible personnel, consisting of firemen, government workers and veterinarians, 61% (97/154) participated in the study. Of those, 13% reported having always worn all PPE-devices during bird collection (PPE-score: 9). Adherence differed between firemen (mean PPE-score: 6.6) and government workers (mean PPE-score: 4.5; p = 0.006). The proportion of personnel always adherent to wearing PPE was lowest for masks (19%). Of the participants, 18% had received seasonal influenza vaccination prior to the outbreak. There were no reports of influenza-like illness. Five sera initially H5-reactive by PN assay were negative by WHO-CC confirmatory testing.

Conclusion

Gaps and variability in adherence demonstrate the risk of exposure to avian influenza under conditions of wild bird collection, and justify serological testing and regular training of task personnel.

Pandemic influenza and farmworkers: the effects of employment, social, and economic factors

Employment, social, and economic factors have the potential to affect the magnitude of an influenza pandemic among farmworkers. Prevention efforts targeted toward livestock farmworkers, including increased access to seasonal influenza vaccine, risk reduction training, various forms of personal protection, and workplace sanitation, are needed. Crop and livestock farmworkers are at increased risk of exposure to influenza A viruses because of limited resources, substandard housing, immigration status, communication and cultural barriers, and discrimination. Recommendations were gathered from migrant clinicians, farmworker advocates, state and federal government agencies, industry stakeholders, and researchers to overcome these barriers, including surveillance of livestock farmworkers, inclusion of farmworker service organizations in planning efforts, and separation of immigration enforcement from emergency assistance.

Past, present, and possible future human infection with influenza virus A subtype H7

These viruses have resulted in >100 cases of human infection since 2002, and their pandemic potential should not be underestimated.

Influenza A subtype H7 viruses have resulted in >100 cases of human infection since 2002 in the Netherlands, Italy, Canada, the United States, and the United Kingdom. Clinical illness from subtype H7 infection ranges from conjunctivitis to mild upper respiratory illness to pneumonia. Although subtype H7 infections have resulted in a smaller proportion of hospitalizations and deaths in humans than those caused by subtype H5N1, some subtype H7 strains appear more adapted for human infection on the basis of their virus-binding properties and illness rates among exposed persons. Moreover, increased isolation of subtype H7 influenza viruses from poultry and the ability of this subtype to cause severe human disease underscore the need for continued surveillance and characterization of these viruses. We review the history of human infection caused by subtype H7. In addition, we discuss recently identified molecular correlates of subtype H7 virus pathogenesis and assess current measures to prevent future subtype H7 virus infection.

Partial direct contact transmission in ferrets of a mallard H7N3 influenza virus with typical avian-like receptor specificity

BACKGROUND

Avian influenza viruses of the H7 subtype have caused multiple outbreaks in domestic poultry and represent a significant threat to public health due to their propensity to occasionally transmit directly from birds to humans. In order to better understand the cross species transmission potential of H7 viruses in nature, we performed biological and molecular characterizations of an H7N3 virus isolated from mallards in Canada in 2001.

RESULTS

Sequence analysis that the HA gene of the mallard H7N3 virus shares 97% identity with the highly pathogenic avian influenza (HPAI) H7N3 virus isolated from a human case in British Columbia, Canada in 2004. The mallard H7N3 virus was able to replicate in quail and chickens, and transmitted efficiently in quail but not in chickens. Interestingly, although this virus showed preferential binding to analogs of avian-like receptors with sialic acid (SA) linked to galactose in an alpha2-3 linkage (SAalpha2-3Gal), it replicated to high titers in cultures of primary human airway epithelial (HAE) cells, comparable to an avian H9N2 influenza virus with human-like alpha2-6 linkage receptors (SAalpha2-6Gal). In addition, the virus replicated in mice and ferrets without prior adaptation and was able to transmit partially among ferrets.

CONCLUSION

Our findings highlight the importance and need for systematic in vitro and in vivo analysis of avian influenza viruses isolated from the natural reservoir in order to define their zoonotic potential.

A pilot study of the immune response to whole inactivated avian influenza H7N1 virus vaccine in mice

Background  Highly pathogenic avian influenza (HPAI) outbreaks in domestic poultry bring humans into close contact with new influenza subtypes and represent a threat to human health. In 1999, an HPAI outbreak of H7N1 virus occurred in domestic poultry in Italy, and a wild‐type virus isolate from this outbreak was chosen as a pandemic vaccine candidate.

Objectives  We conducted a pilot study to investigate the kinetics of the humoral immune response induced after immunisation with an egg grown whole inactivated H7N1 virus vaccine in BALB/c mice.

Methods  Mice were vaccinated with one or two doses of H7N1 vaccine (15 μg total protein) to investigate the influenza specific antibody secreting cell (IS‐ASC) and serum antibody responses.

Results  After the first dose of vaccine, only IgM IS‐ASC were detected in the spleen and bone marrow, whereas IgG, IgA and IgM IS‐ASC were found after the second dose. Low antibody titres were detected after the first immunisation, whilst the second dose of vaccine significantly boosted the HI (range 128–512), neutralising and IgG antibody titres. The IgG subclass response was dominated by IgG2a indicating a dominant Th1 response after the first vaccination, whereas a more mixed Th1/Th2 profile was observed after the second dose.

Conclusions  This pilot study shows the value of using a number of immunological methods to evaluate the quality of the immune response to potential pandemic candidate vaccines.

A cell-based H7N1 split influenza virion vaccine confers protection in mouse and ferret challenge models

BACKGROUND

In recent years, several avian influenza subtypes (H5, H7 and H9) have transmitted directly from birds to man, posing a pandemic threat.

OBJECTIVES

We have investigated the immunogenicity and protective efficacy of a cell based candidate pandemic influenza H7 vaccine in pre-clinical animal models.

METHODS

Mice and ferrets were immunised with two doses of the split virus vaccine (12-24 microg haemagglutinin) with or without aluminium hydroxide adjuvant and challenged 3 weeks after second dose with the highly pathogenic A/chicken/Italy/13474/99 (H7N1) virus. The H7N1-specific serum antibody response was also measured. After challenge, viral shedding, weight loss, disease signs and death (only mice) were recorded.

RESULTS

Low-to-modest serum antibody titres were detected after vaccination. Nevertheless, the vaccine induced significant protection from disease after challenge with the wild-type virus. In the murine lethal challenge model, vaccination effectively prevented death and, furthermore, formulation with adjuvant reduced excessive weight loss and viral shedding. In ferrets, vaccination reduced viral shedding and protected against systemic spread of the virus.

CONCLUSIONS

We have extended to the H7 subtype the finding that protective efficacy may not be directly correlated with the pre-challenge levels of serum antibodies, a finding which could be of great importance in assessing the potential effectiveness of pandemic influenza vaccines.

Personal protective equipment and risk for avian influenza (H7N3)

An outbreak of avian influenza (H7N3) among poultry resulted in laboratory-confirmed disease in 1 of 103 exposed persons. Incomplete use of personal protective equipment (PPE) was associated with conjunctivitis and influenza-like symptoms. Rigorous use of PPE by persons managing avian influenza outbreaks may reduce exposure to potentially hazardous infected poultry materials.

Protecting poultry workers from exposure to avian influenza viruses

Emerging zoonotic diseases are of increasing regional and global importance. Preventing occupational exposure to zoonotic diseases protects workers as well as their families, communities, and the public health. Workers can be protected from zoonotic diseases most effectively by preventing and controlling diseases in animals, reducing workplace exposures, and educating workers. Certain avian influenza viruses are potential zoonotic disease agents that may be transmitted from infected birds to humans. Poultry workers are at risk of becoming infected with these viruses if they are exposed to infected birds or virus-contaminated materials or environments. Critical components of worker protection include educating employers and training poultry workers about occupational exposure to avian influenza viruses. Other recommendations for protecting poultry workers include the use of good hygiene and work practices, personal protective clothing and equipment, vaccination for seasonal influenza viruses, antiviral medication, and medical surveillance. Current recommendations for protecting poultry workers from exposure to avian influenza viruses are summarized in this article.

Adherence with oseltamivir chemoprophylaxis among workers exposed to poultry during avian influenza outbreaks in southern Israel

OBJECTIVES

To determine adherence with recommended pre- and post-exposure oseltamivir prophylaxis (OP) among workers exposed to poultry during five simultaneous avian influenza (AI) H5N1 outbreaks in poultry farms in southern Israel in March 2006, as well as the efficiency of the distribution system of oseltamivir in the community.

DESIGN

Epidemiological investigation identified 201 workers exposed to poultry during AI outbreaks. They were interviewed by a public health nurse regarding adherence with recommended OP, symptoms, and possible side effects. Data were collected on type of exposure, age, sex, rate of adherence with OP, and reasons for non-adherence. For eight workers, paired sera were drawn for the determination of antibodies to H5. Data were collected on the efficiency of the distribution of oseltamivir tablets to workers in the community.

RESULTS

High adherence with OP (87.6%) was found among poultry workers during outbreaks of AI, with no difference by type of exposure, age, or sex. There was a low rate of side effects of OP (1.5%). No exposed workers developed AI and none of the eight who had paired sera drawn showed seroconversion. The distribution of OP in the community was inefficient, with 27.7% of the tablets 'lost' or returned unusable.

CONCLUSIONS

These data emphasize the importance of developing efficient targeted distribution systems in the community for OP, in order to prevent human infection during AI outbreaks.

Swine influenza (H3N2) infection in a child and possible community transmission, Canada

Seropositivity to the same strain was demonstrated in the child and in multiple other community members.

An influenza A virus (H3N2) of probable swine origin, designated A/Canada/1158/2006, was isolated from a 7-month-old hospitalized child who lived on a communal farm in Canada. The child recovered uneventfully. A serosurvey that used a hemagglutination-inhibition assay for A/Canada/1158/2006 was conducted on 54 of the 90 members of the farm. Seropositivity was demonstrated in the index patient, 4 of 7 household members, and 4 of 46 nonhousehold members; none had a history of hospital admission for respiratory illness in the preceding year. Serologic evidence for this strain of swine influenza was also found in 1 of 10 pigs (12 weeks–6 months of age) on the farm. Human infection with swine influenza virus is underrecognized in Canada, and because viral strains could adapt or reassort into a form that results in efficient human-to-human transmission, routine surveillance of swine workers should be considered as part of pandemic influenza preparedness.

Spatial clustering of swine influenza in Ontario on the basis of herd-level disease status with different misclassification errors

This approach maximizes sensitivity of serology-based monitoring systems by considering spatial clustering of herds classified as false positive by herd testing, allowing outbreaks to be detected in an early phase. The primary objective of this study was to determine whether swine herds infected with influenza viruses cluster in space, and if so, where they cluster. The secondary objective was to investigate the combining of a multivariate spatial scan statistic with herd test results to maximize the sensitivity of the surveillance system for swine influenza. We tested for spatial clustering of swine influenza using the Cuzick-Edwards test as a global test. The location of the most likely spatial clusters of cases for each subtype and strain in a sample of 65 sow and 72 finisher herds in 2001 (Ontario, Canada), and 76 sow herds in 2003 (Ontario, Canada) was determined by a spatial scan statistic in a purely spatial Bernoulli model based on single and multiple datasets. A case herd was defined by true herd-disease status for sow or finisher herds tested for H1N1, and by apparent herd-disease status for sow herds tested for two H3N2 strains (A/Swine/Colorado/1/77 (Sw/Col/77) and A/Swine/Texas/4199-2/98 (Sw/Tex/98)). In sow herds, there was no statistically significant clustering of H1N1 influenza after adjustment for pig-farm density. Similarly, spatial clustering was not found in finisher herds. In contrast, clustering of H3N2 Sw/Col/77 (prevalence ratio=12.5) and H3N2 Sw/Tex/98 (prevalence ratio=15) was identified in an area close to a region with documented isolation of avian influenza isolates from pigs. For the H1N1 subtype tested by ELISA, we used an approach that minimized overall misclassification at the herd level. This could be more applicable for detecting clusters of positive farms when herd prevalence is moderate to high than when herd prevalence is low. For the H3N2 strains we used an approach that maximized herd-level sensitivity by minimizing the herd cut-off. This is useful in situations where prevalence of the pathogen is low. The results of applying a multivariate spatial scan statistic approach, led us to generate the hypothesis that an unknown variant of influenza of avian origin was circulating in swine herds close to an area where avian strains had previously been isolated from swine. Maximizing herd sensitivity and linking it with the spatial information can be of use for monitoring of pathogens that exhibit the potential for rapid antigenic change, which, consequently, might then lead to diminished cross-reactivity of routinely used assays and lower test sensitivity for the newly emerged variants. Veterinary authorities might incorporate this approach into animal disease surveillance programs that either substantiate freedom from disease, or are aimed at detecting early incursion of a pathogen, such as influenza virus, or both.