Abstract
BackgroundFew studies have reported on the seroprevalence of antibodies against avian influenza A (H9N2) virus and the incidence of these infections in the northern China and among swine workers.MethodsWe conducted a serological cohort study among people working with poultry or swine or the general population in Beijing, China. It comprised four cross‐sectional serological surveys in November 2013, April 2014, April 2015, and April 2016. Blood samples collected from the participants were tested for anti‐H9N2 antibodies using a hemagglutination‐inhibition (HI) assay. Multivariable Poisson regression model was then used to compare the person‐month incidence rates for H9N2 viral infections among the three groups, assessed by incidence rate ratio (IRR).ResultsIn the four cross‐sectional surveys, the highest seroprevalence of anti‐H9N2 antibodies (HI titer ≥ 80) was recorded in the poultry workers (2.77%, 19/685) in April 2016, while the lowest was recorded in the general population (0.09%, 1/1135) in April 2015. The highest incidence density rate for H9N2 infections across the whole study period was recorded among the poultry workers (3.75/1000 person‐months), followed by the swine workers (1.94/1000 person‐months) and the general population (1.78/1000 person‐months). Multivariable analysis showed that the poultry workers were at higher risk (IRR: 2.42, 95% CI: 1.07‐5.48; P = 0.034) of contracting H9N2 virus than the general population.ConclusionsAlthough the seroprevalence of H9N2 antibodies was low in Beijing, the poultry workers were at higher risk of contracting H9N2 viral infections than the general population. Closer monitoring and strengthened protection measures for poultry workers are warranted.
Highlights
The first recorded avian influenza A (H9N2) virus infections oc‐ curred in 1966 among turkeys in the United States.[1]
The hemagglutination (HA) gene sequences from the influenza virus resource database at the US National Center of Biotechnology Information (NCBI) indicate that more than 90% of the globally isolated H9N2 viruses come from Asia, of which 78% come from China.[11]
Poisson regression analysis showed that the poultry workers were at higher risk (IRR: 2.42, 95% CI: 1.07‐5.48; P = 0.034) of contracting H9N2 than the general population (Table 4), but no statistically significant difference was identified between the swine workers and general population (IRR: 0.35, 95% CI: 0.09‐1.36; P = 0.128)
Summary
Few studies have reported on the seroprevalence of antibodies against avian influenza A (H9N2) virus and the incidence of these infections in the northern China and among swine workers. Methods: We conducted a serological cohort study among people working with poultry or swine or the general population in Beijing, China. It comprised four cross‐ sectional serological surveys in November 2013, April 2014, April 2015, and April 2016. Conclusions: the seroprevalence of H9N2 antibodies was low in Beijing, the poultry workers were at higher risk of contracting H9N2 viral infections than the general population.
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