Abstract
The continued spread of highly pathogenic avian influenza (HPAI) viruses of H5 and H7 subtypes and low pathogenic avian influenza (LPAI) viruses of H5, H7 and H9 subtypes in birds and the subsequent infections in humans pose an ongoing pandemic threat. It has been proposed that poultry workers are at higher risk of exposure to HPAI or LPAI viruses and subsequently infection due to their repeated exposure to chickens or domestic waterfowl. The aim of this study was to examine the seroprevalence of antibodies against H5, H7 and H9 viruses amongst duck-related workers in Beijing, China and the risk factors associated with seropositivity. In March, 2011, 1741 participants were recruited from (1) commercial duck-breeding farms; (2) private duck-breeding farms; and (3) duck-slaughtering farms. Local villagers who bred ducks in their backyards were also recruited. A survey was administered by face-to-face interview, and blood samples were collected from subjects for antibody testing against H5, H7 and H9 viruses. We found that none of the subjects were seropositive for either H5 or H7 viruses, and only 0.7% (12/1741) had antibody against H9. A statistically significant difference in H9 antibody seroprevalence existed between the various categories of workers (P = 0.005), with the highest figures recorded amongst the villagers (1.7%). Independent risk factors associated with seropositivity toinfection with H9 virus included less frequent disinfection of worksite (OR, 5.13 [95% CI, 1.07–24.58]; P = 0.041; ≤ twice monthly versus>twice monthly) and handling ducks with wounds on hands (OR, 4.13 [95% CI, 1.26–13.57]; P = 0.019). Whilst the risk of infection with H5, H7 and H9 viruses appears to be low among duck-related workers in Beijing, China, ongoing monitoring of infection with the H9 virus is still warranted, especially amongst villagers who breed backyard ducks to monitor for any changes.
Highlights
The spread of highly pathogenic avian influenza (HPAI) viruses of H5 or H7 subtypes and low pathogenic avian influenza (LPAI) viruses of H5, H7 or H9 subtypes amongst birds and sporadic infection in humans continues to pose a threat to public health [1,2,3,4,5,6,7,8,9,10], because of the potential for a strain with pandemic potential to emerge via adaptive mutation or reassortment [11]
While the last pandemic originated from a swine-origin influenza virus (S-OIV) [15], the threat brought by avian influenza viruses continues
No statistically significant difference was found for H9 seroprevalence between the sexes (P = 0.892), but a difference was found between age groups (P = 0.021), with the higher seroprevalence recorded for subjects above 50 years (1.5%, 8/550)
Summary
The spread of highly pathogenic avian influenza (HPAI) viruses of H5 or H7 subtypes and low pathogenic avian influenza (LPAI) viruses of H5, H7 or H9 subtypes amongst birds and sporadic infection in humans continues to pose a threat to public health [1,2,3,4,5,6,7,8,9,10], because of the potential for a strain with pandemic potential to emerge via adaptive mutation or reassortment [11]. The 1918 pandemic begun following adaptive mutation of an avian virus, and the pandemics of 1957 and 1968 were the result of genetic reassortment of viruses from human and avian sources [12,13,14]. In 1996, a woman developed conjunctivitis after a piece of straw had entered her eye while cleaning her duck house, with LPAI
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