A Cross-Sectional Virological and Sero-Epidemiological Study of Exposures to Avian Influenza A(H5N1) and A(H9N2) Viruses in Live Bird Market Workers in Dhaka, Bangladesh.

BACKGROUND

Avian influenza A viruses (AIVs) are endemic among poultry in Bangladesh sold at live bird markets (LBMs). We assessed virologic and serologic evidence of exposure to AIVs among LBM workers.

METHODS

A cross-sectional study recruited 702 randomly sampled workers from 42 LBMs in Dhaka, Bangladesh, during 2017. Nasal and throat swabs collected from workers and air samples from LBMs were tested for influenza A virus by RT-PCR with positives subtyped for A(H5), A(H7), and A(H9). Baseline sera from 695 workers and follow-up sera from 89 workers with influenza A positive respiratory specimens were tested by microneutralization assay for antibodies to A(H5N1) clade 2.3.2.1a and A(H9N2) G1 lineage viruses circulating in poultry. A seropositive result was defined as a neutralizing antibody titer ≥ 1:40.

RESULTS

Most LBM workers reported slaughtering (93.3%) and defeathering (84.5%) poultry. Ninety-nine (14.1%) had ≥ 1 respiratory specimen that tested influenza A positive but negative for A(H1) and A(H3). Of these 99, subtyping identified 28 (28.3%) A(H9), 2 (2%) A(H5), 3 (3%) both A(H5) and A(H9), and 66 (66.7%) A (nonsubtypeable). Influenza A viruses were detected in air samples at 25 LBMs (59.5%), including A(H9) only in 10 LBMs (40%), A(H5) only in one (4%), both A(H5) and A(H9) in 13 (52%), and one A (nonsubtypeable) (4%). None of the participants were seropositive for AIVs.

CONCLUSIONS

LBM workers had extensive exposure to AIVs, but none had serologic evidence of infection with A(H5N1) or A(H9N2) viruses circulating among poultry in Bangladesh. Ongoing surveillance of AIVs in LBMs and poultry workers is needed.