Evidence for avian H9N2 influenza virus infections among rural villagers in Cambodia

Southeast Asia remains a critical region for the emergence of novel and/or zoonotic influenza, underscoring the importance of extensive sampling in rural areas where early transmission is most likely to occur. In 2008, 800 adult participants from eight sites were enrolled in a prospective population-based study of avian influenza [AI] virus transmission where highly pathogenic avian influenza [HPAI] H5N1 virus had been reported in humans and poultry from 2006 to 2008. From their enrollment sera and questionnaires, we report risk factor findings for serologic evidence of previous infection with 18 AI virus strains. Serologic assays revealed no evidence of previous infection with 13 different low-pathogenic AI viruses or with HPAI avian-like A/Cambodia/R0404050/2007[H5N1]. However, 21 participants had elevated antibodies against avian-like A/Hong Kong/1073/1999[H9N2], validated with a monoclonal antibody blocking ELISA assay specific for avian H9. Although cross-reaction from antibodies against human influenza viruses cannot be completely excluded, the study data suggest that a number of participants were previously infected with the avian-like A/Hong Kong/1073/1999[H9N2] virus, likely due to as yet unidentified environmental exposures. Prospective data from this cohort will help us better understand the serology of zoonotic influenza infection in a rural cohort in SE Asia

Serological evidence for avian H9N2 influenza virus infections among Romanian agriculture workers

In recent years, wild birds have introduced multiple highly pathogenic avian influenza [HPAI] H5N1 virus infections in Romanian poultry. In 2005 HPAI infections were widespread among domestic poultry and anecdotal reports suggested domestic pigs may also have been exposed. We sought to examine evidence for zoonotic influenza infections among Romanian agriculture workers. Between 2009 and 2010, 363 adult participants were enrolled in a cross-sectional, seroepidemiological study. Confined animal feeding operation [CAFO] swine workers in Tulcea and small, traditional backyard farmers in Cluj-Napoca were enrolled, as well as a non-animal exposed control group from Cluj-Napoca. Enrollment sera were examined for serological evidence of previous infection with 9 avian and 3 human influenza virus strains. Serologic assays showed no evidence of previous infection with 7 low pathogenic avian influenza viruses or with HPAI H5N1. However, 33 participants [9.1%] had elevated microneutralization antibody titers against avian-like A/Hong Kong/1073/1999[H9N2], 5 with titers >/= 1:80 whom all reported exposure to poultry. Moderate poultry exposure was significantly associated with elevated titers after controlling for the subjects' age [adjusted OR = 3.6; 95% CI, 1.1-12.1]. There was no evidence that previous infection with human H3N2 or H2N2 viruses were confounding the H9N2 seroreactivity. These data suggest that H9N2 virus may have circulated in Romanian poultry and occasionally infected man