Christine M. Szablewski’s research while affiliated with Centers for Disease Control and Prevention and other places

Since late 2021, outbreaks of highly pathogenic avian influenza virus have caused a record number of mortalities in wild birds, domestic poultry, and mammals in North America. Wetlands are plausible environmental reservoirs of avian influenza virus; however, the transmission and persistence of the virus in the aquatic environment are poorly understood. To explore environmental contamination with the avian influenza virus, a large-volume concentration method for detecting infectious avian influenza virus in waterbodies was developed. A variety of filtering, elution, and concentration methods were explored, in addition to testing filtering speeds using artificially amended 20 L water matrices (deionized water with sterile dust, autoclaved wetland water, and wetland water). The optimal protocol was dead-end ultrafiltration coupled with salt solution elution and centrifugation concentration. Using this method, infectious virus was recovered at 1 × 10⁻¹ 50% egg infectious dose per milliliter (EID50/mL), whereas viral RNA was detected inconsistently down to 1 × 10⁰ EID50/mL. This method will aid in furthering our understanding of the avian influenza virus in the environment and may be applicable to the environmental detection of other enveloped viruses.

Following the detection of highly pathogenic avian influenza (HPAI) virus in countries bordering Kenya to the west, we conducted surveillance among domestic and wild birds along the shores of Lake Victoria. In addition, between 2018 and 2020, we conducted surveillance among poultry and poultry workers in live bird markets and among wild migratory birds in various lakes that are resting sites during migration to assess introduction and circulation of avian influenza viruses in these populations. We tested 7464 specimens (oropharyngeal (OP) and cloacal specimens) from poultry and 6531 fresh fecal specimens from wild birds for influenza A viruses by real-time RT-PCR. Influenza was detected in 3.9% (n = 292) of specimens collected from poultry and 0.2% (n = 10) of fecal specimens from wild birds. On hemagglutinin subtyping, most of the influenza A positives from poultry (274/292, 93.8%) were H9. Of 34 H9 specimens randomly selected for further subtyping, all were H9N2. On phylogenetic analysis, these viruses were genetically similar to other H9 viruses detected in East Africa. Only two of the ten influenza A-positive specimens from the wild bird fecal specimens were successfully subtyped; sequencing analysis of one specimen collected in 2018 was identified as a low-pathogenicity avian influenza H5N2 virus of the Eurasian lineage, and the second specimen, collected in 2020, was subtyped as H11. A total of 18 OP and nasal specimens from poultry workers with acute respiratory illness (12%) were collected; none were positive for influenza A virus. We observed significant circulation of H9N2 influenza viruses in poultry in live bird markets in Kenya. During the same period, low-pathogenic H5N2 virus was detected in a fecal specimen collected in a site hosting a variety of migratory and resident birds. Although HPAI H5N8 was not detected in this survey, these results highlight the potential for the introduction and establishment of highly pathogenic avian influenza viruses in poultry populations and the associated risk of spillover to human populations.

Following the detection of highly pathogenic avian influenza (HPAI) virus in countries bordering Kenya to the west, we conducted surveillance among domestic and wild birds along the shores of Lake Victoria. In addition, between 2018 and 2020, we conducted surveillance among poultry and poultry workers in live bird markets and among wild migratory birds in various lakes that are resting sites during migration to assess introduction and circulation of avian influenza viruses in these populations. We tested 7,464 specimens (oropharyngeal and cloacal swabs) from poultry and 6,531 fresh fecal specimens from wild birds for influenza A viruses by real-time RT-PCR. Influenza was detected in 3.9% (n=292) of specimens collected from poultry and 0.2% (n=10) of fecal specimens from wild birds. On hemagglutinin subtyping, most of the influenza A positives from poultry (274/292, 93.8%) were H9. Of 34 H9 specimens randomly selected for further subtyping, all were H9N2. On phylogenetic analysis, these viruses were genetically similar to other H9 viruses detected in East Africa. Only two of the ten influenza A positive specimens from the wild bird fecal specimens were successfully subtyped; sequencing analysis of one specimen collected in 2018 was identified as low pathogenicity avian influenza H5N2 virus of the Eurasian lineage and the second specimen, collected in 2020, was subtyped as H11. A total of 18 OP/NS swabs from poultry workers with ARI (12%) were collected; none were positive for influenza A virus. We observed significant circulation of H9N2 influenza viruses in poultry in live bird markets in Kenya. During the same period, low pathogenic H5N2 virus was detected in a fecal specimen collected in a site hosting a variety of migratory and resident birds. Although HPAI H5N8 was not detected in this survey, these results highlight the potential for introduction and establishment of highly pathogenic avian influenza viruses in poultry populations and the associated risk of spillover to human populations.

Aims Swine are a mixing vessel for the emergence of novel reassortant influenza A viruses (IAV). Interspecies transmission of swine‐origin IAV poses a public health and pandemic risk. In the United States, the majority of zoonotic IAV transmission events have occurred in association with swine exposure at agricultural fairs. Accordingly, this human‐animal interface necessitates mitigation strategies informed by understanding of interspecies transmission mechanisms in exhibition swine. Likewise, the diversity of IAV in swine can be a source for novel reassortant or mutated viruses that pose a risk to both swine and human health. Methods and Results In an effort to better understand those risks, here we investigated the epidemiology of IAV in exhibition swine and subsequent transmission to humans by performing phylogenetic analyses using full genome sequences from 272 IAV isolates collected from exhibition swine and 23 A(H3N2)v viruses from human hosts during 2013–2015. Sixty‐seven fairs (24.2%) had at least one pig test positive for IAV with an overall estimated prevalence of 8.9% (95% CI: 8.3–9.6, Clopper‐Pearson). Of the 19 genotypes found in swine, 5 were also identified in humans. There was a positive correlation between the number of human cases of a genotype and its prevalence in exhibition swine. Additionally, we demonstrated that A(H3N2)v viruses clustered tightly with exhibition swine viruses that were prevalent in the same year. Conclusions These data indicate that multiple genotypes of swine‐lineage IAV have infected humans, and highly prevalent IAV genotypes in exhibition swine during a given year are also the strains detected most frequently in human cases of variant IAV. Continued surveillance and rapid characterization of IAVs in exhibition swine can facilitate timely phenotypic evaluation and matching of candidate vaccine strains to those viruses present at the human‐animal interface which are most likely to spillover into humans.

Avian influenza viruses (AIVs) infect both wild birds and domestic poultry, resulting in economically costly outbreaks that have the potential to impact public health. Currently, a knowledge gap exists regarding the detection of infectious AIVs in the aquatic environment. In response to the 2021–2022 Eurasian strain highly pathogenic avian influenza (HPAI) A/goose/Guangdong/1/1996 clade 2.3.4.4 lineage H5 outbreak, an AIV environmental outbreak response study was conducted using a One Health approach. An optimized method was used to temporally sample (April and May 2022) and analyze (culture and molecular methods) surface water from five water bodies (four wetlands and one lake used as a comparison location) in areas near confirmed HPAI detections in wild bird or poultry operations. Avian influenza viruses were isolated from water samples collected in April from all four wetlands (not from the comparison lake sample); HPAI H5N1 was isolated from one wetland. No virus was isolated from the May samples. Several factors, including increased water temperatures, precipitation, biotic and abiotic factors, and absence of AIV-contaminated fecal material due to fewer waterfowl present, may have contributed to the lack of virus isolation from May samples. Results demonstrate surface water as a plausible medium for transmission of AIVs, including the HPAI virus.

Background Avian influenza (AI) virus detections occurred frequently in 2022 and continue to pose a health, economic, and food security risk. The most recent global analysis of official reports of animal outbreaks and human infections with all reportable AI viruses was published almost a decade ago. Increased or renewed reports of AI viruses, especially high pathogenicity H5N8 and H5N1 in birds and H5N1, H5N8, and H5N6 in humans globally, have established the need for a comprehensive review of current global AI virus surveillance data to assess the pandemic risk of AI viruses. Objective This study aims to provide an analysis of global AI animal outbreak and human case surveillance information from the last decade by describing the circulating virus subtypes, regions and temporal trends in reporting, and country characteristics associated with AI virus outbreak reporting in animals; surveillance and reporting gaps for animals and humans are identified. Methods We analyzed AI virus infection reports among animals and humans submitted to animal and public health authorities from January 2013 to June 2022 and compared them with reports from January 2005 to December 2012. A multivariable regression analysis was used to evaluate associations between variables of interest and reported AI virus animal outbreaks. ResultsFrom 2013 to 2022, 52.2% (95/182) of World Organisation for Animal Health (WOAH) Member Countries identified 34 AI virus subtypes during 21,249 outbreaks. The most frequently reported subtypes were high pathogenicity AI H5N1 (10,079/21,249, 47.43%) and H5N8 (6722/21,249, 31.63%). A total of 10 high pathogenicity AI and 6 low pathogenicity AI virus subtypes were reported to the WOAH for the first time during 2013-2022. AI outbreaks in animals occurred in 26 more Member Countries than reported in the previous 8 years. Decreasing World Bank income classification was significantly associated with decreases in reported AI outbreaks (P

BACKGROUND Avian influenza (AI) outbreaks occurred frequently in 2022 and continue to pose a health, economic, and food security risk. A comprehensive review of current global AI surveillance information is key to assessing the pandemic risk of AI viruses. OBJECTIVE We provide an analysis of global AI surveillance information from the last decade and identify risk factors of interest and surveillance gaps. METHODS We compared AI reports submitted to animal and public health authorities from January 2013 – June 2022 to January 2005 – December 2012. A multivariable regression analysis was used to evaluate associations between risk factors of interest and reported animal AI outbreaks. RESULTS From 2013–2022, 52% (95/182) of World Organization for Animal Health (WOAH) member-states identified 34 AI virus subtypes during 21,249 outbreaks. The most frequently reported subtypes were high pathogenic AI H5N1 (10,079, 47.4%) and H5N8 (6,722, 31.6%). Ten high pathogenic AI and six low pathogenic AI virus subtypes were reported to WOAH for the first time during 2013–2022. One in four member-states (26/95) did not report an outbreak prior to 2013. AI outbreaks in animals occurred in 26 more countries than reported in the previous eight years. Decreasing World Bank income classification was significantly associated with decreases in reported AI outbreaks. Seventeen (8.8%, 17/194) World Health Organization (WHO) member-states reported 2,000 human AI virus infections of 10 virus subtypes. H7N9 (1,568, 78.4%) and H5N1 (254, 12.7%) viruses accounted for the most human infections. Eight member-states did not report a human case prior to 2013. Of 1,953 human cases with available information, 75% (1,461/1,953) had a known animal exposure. The median time from illness onset to the notification posted on the WHO event information site was 15 days (IQR=21, Average= 23). Seasonality patterns of bird outbreaks and human infections with AI viruses were very similar, occurred year-round, and peaked during November through May. CONCLUSIONS Our analysis suggests that AI outbreaks are more frequent and geographically widespread than in the past. Global surveillance gaps include reporting delays and inconsistent reporting from all regions. Continued monitoring for AI outbreaks in animals and human infections with AI viruses is crucial for pandemic preparedness.

Due to their documented epidemiological relevance as hosts for influenza A viruses (IAV), humans, poultry and pigs in backyard production systems (BPS) within wetlands could be key to the emergence of novel IAV variants able to transmit between humans or animals. To better understand the circulation of IAV at the human–animal interface of BPS within wetlands, we studied IAV in backyard duck flocks and pig herds in the Pacific Coast of Guatemala. From April 2013 to October 2014, we estimated the monthly IAV per cent seropositive and viral positive flocks and herds in two resource‐limited communities. We detected antibodies in sera against the IAV nucleoprotein through ELISA. We also detected IAV viral RNA in respiratory (ducks and pigs) and cloacal (ducks) swabs through rRT‐PCR directed at the matrix gene. We attempted viral isolation in eggs or MDCK cells followed by sequencing from swabs positive for IAV. During our study period, IAV seropositivity in duck flocks was 38%, and viral positivity was 23% (n = 86 BPS sampled). IAV seropositivity in pig herds was 42%, and viral positivity was 20% (n = 90 BPS sampled). Both flocks and herds had detectable antibodies against IAV mostly year‐round, and IAV was detected in several months. We isolated an H3N2 virus from one pig sampled at the end of 2013. Standard nucleotide BLAST searches indicate that the isolated virus was similar to seasonal viruses circulating in humans, suggesting human‐to‐pig transmission. Our data show concurrent circulation of IAV in multiple species of poultry and pigs that were commingled in rudimentary conditions in proximity to humans, but no significant risk factors could be identified.