A total of 305 serum specimens were collected from 305 workers who were in close contact with poultry populations during May 2009–March 2010. Influenza strains A/duck/Huabei/01/2007 (H5N1), belonging to clade 2.3.4, and A/chicken/Shangdong/ZB/2007 (H9N2) of the F/98 genotype were used for the microneutralization assay, which was performed as described (2,3). The F/98 genotype (H9N2) and clade 2.3.4 (H5N1) viruses had been demonstrated to be the predominant strains circulating in poultry in this region and were responsible for most cases of human infection during the period of the survey (4,5). Therefore, we only used the 2 viral strains in the MN assay.

Serum samples were considered positive if titers were >80, and all results were generated from at least 2 independent assays. Simultaneously, the 305 surveyed workers were administered questionnaires to ascertain avian influenza–related KAPs. Among the distributed questionnaires, responses from 207 were considered valid and were used for further analysis. Epi Info software, version 3.5.4 (Centers for Disease Control and Prevention, Atlanta, GA, USA), was used to analyze the survey data. The Pearson χ² test was used to compare differences between groups. Differences were considered significant if p value was <0.05.

Of the 305 poultry workers, 155 (50.8%) were duck keepers from 8 farms, 114 (37.4%) were chicken keepers from 5 farms, and 36 (11.8%) were chicken butchers who worked at an abattoir. The duck and chicken farms were located in different districts in Beijing. One hundred and fifty-five (50.8%) workers were male, and 150 (49.2%) were female; 147 (48.2%) participants were 36–45 years of age, 76 (24.9%) were 18–35 years, and 82 (26.9%) were >45 years. All participants had no history of vaccination for seasonal influenza in the past 3 years. MN assay revealed that no workers were positive for antibodies against influenza virus subtype H5, whereas 14 (4.6%) were positive for antibodies against subtype H9; titers ranged from 80 to 640 (Figure). Further analysis indicated that proportions of seropositive workers were 2.6% (4/155) for men and 6.7% (10/150) for women. By age, the proportions of seropositive poultry workers were 9.2% (7/76) for those 18–35 years, 2.7% (4/147) for those 36–45-years, and 3.7% (3/82) for those >45 years of age. These results suggest that subtype H9N2 virus infection was more prevalent among persons 18–35 years of age. The proportions of seropositive duck keepers, chicken keepers, and chicken butchers were 3.9% (6/155), 3.5% (4/114), and 11.1% (4/36), respectively. No significant differences were found in the infection rate among the 3 groups.

A total of 207 poultry workers completed a questionnaire regarding KAPs related to avian influenza. In terms of knowledge of avian influenza, 181 (87.4%) of workers recognized the transmission route through the respiratory tract, 113 (54.6%) recognized the transmission route through the gastrointestinal tract, and 117 (56.5%) recognized the transmission route through the mucosa. Nearly half of the participants ignored the latter 2 major transmission routes. In terms of knowledge of poultry housing practices, 135 (65.2%) and 160 (77.3%) of the workers had the correct understanding that chickens and ducks should not be raised with pigs in the same backyards and that poultry should not have contact with wild birds. Furthermore, 181 (87.4%) of the participants knew that eating and selling dead birds was against health regulations, and 167 (80.7%) knew that improving vaccination coverage and quality is an effective strategy for preventing AIV infection. Significant discrepancies were observed among groups with different educational levels in knowledge of avian influenza (except for those who understood that infection occurred through the respiratory tract and mucosa) (p<0.05) (Table 1). Workers with a high level of education (senior high school, university or college, and above) had more correct answers to the corresponding questions. Significant differences were also found between groups of different ages and occupations regarding knowledge of avoiding mixed housing practices (p<0.05). Most (79.0%–95.0%) young persons, 18–35 years of age, knew that poultry should not be kept in mixed housing with pigs nor kept in contact with other species of birds. Also concerning the above 2 risks, chicken keepers had more accurate knowledge than duck keepers (Table 1). No significant differences were found between men and women in terms of general knowledge (p>0.05).

Regarding attitudes toward avian influenza, 116 (56.0%) of 207 surveyed workers did not consider that AIVs pose a public health threat. They also rarely showed concern for the consequences resulting from avian influenza.

Analysis of practices concerning avian influenza prevention among 207 poultry workers is shown in Table 2. Although 184 (88.9%) respondents said they wore specific work clothing, wearing personal protective equipment was not a routine practice among poultry workers: only 112 (54.1%) wore gloves, and 95 (45.9%) wore masks. We also found that 165 (79.7%) participants routinely washed their hands after work and that 174 (84.1%) workers regularly used disinfectant. Significant differences were found between chicken keepers and duck keepers; the former were more likely to follow good hygiene practices than were the latter (p<0.01) (Table 2).

Transmission of AIVs from poultry to humans probably results from contact with infected poultry or contaminated materials (6–9). Workers in the poultry industry are at high risk for AIV infection. We found that 4.6% of poultry workers in Beijing had antibodies against influenza virus subtype H9. These findings indicate that viruses of subtype H9 may have previously infected a considerable number of persons in China, thus highlighting the potential public health risk for H9 AIV. None of the poultry workers in our study had positive test results for H5. Similarly, previous serologic surveillance studies in China showed that the prevalence of antibodies against H5 strains was significantly lower than that for antibodies against H9 (10,11).