Background.?In Indonesia, highly pathogenic avian influenza A(H5N1) virus has become endemic in poultry, and has caused sporadic deadly infections in human. Since 2012 we have conducted fixed-point surveillance of avian influenza viruses at a live poultry market in East Java, Indonesia. In this study we examined the seroprevalence of the virus infection among market workers.

Methods.?Sera were collected from 101 workers in early 2014 and examined for antibody activity against avian A(H5N1) Eurasian lineage virus by hemagglutination inhibition (HI) assay.

Results.?By the HI assay, 84% of the sera tested positive for antibody activity against the avian virus. Further analysis revealed the average HI titer in 2014 to be 2.9-fold higher than in 2012 and that seroconversion occurred in 44% of paired sera (11/25) between 2012 and 2014. A medical history survey was carried out in 2016; responses to questionnaires indicated that none of workers had suffered from severe acute respiratory illness during 2013.

Conclusions.?This study provides evidence of a high prevalence of avian A(H5N1) virus infection in 2013 among workers of a live poultry market. However no instances of hospitalizations were reported, we can therefore conclude the virus did not manifest any clinical symptoms in workers.