Estimating Risks of Inapparent Avian Exposure for Human Infection: Avian Influenza Virus A (H7N9) in Zhejiang Province, China

Abstract

Inapparent avian exposure was suspected for the sporadic infection of avian influenza A(H7N9) occurring in China. This type of exposure is usually unnoticed and difficult to model and measure. Infected poultry with avian influenza H7N9 virus typically remains asymptomatic, which may facilitate infection through inapparent poultry/bird exposure, especially in a country with widespread practice of backyard poultry. The present study proposed a novel approach that integrated ecological and case-control methods to quantify the risk of inapparent avian exposure on human H7N9 infection. Significant associations of the infection with chicken and goose densities, but not with duck density, were identified after adjusting for spatial clustering effects of the H7N9 cases across multiple geographic scales of neighborhood, community, district and city levels. These exposure risks varied geographically in association with proximity to rivers and lakes that were also proxies for inapparent exposure to avian-related environment. Males, elderly people, and farmers were high-risk subgroups for the virus infection. These findings enable health officials to target educational programs and awareness training in specific locations to reduce the risks of inapparent exposure.

Epidemiological and clinical characteristics of humans with avian influenza A (H7N9) infection in Guangdong, China, 2013–2017

“…In addition, the current study demonstrated that the maleto-female ratio of patients was approximately 2.0:1, and this pattern is consistent with results of previous studies (Sun et al, 2014;Chen et al, 2013c). An explanation for these results is that Chinese men are more likely to engage in selling or slaughtering live poultry than women (Cowling et al, 2013); another explanation may be that most Asian males have birdrelated hobbies, and they probably visit LPMs frequently and keep pet birds at home (Ge et al, 2017); all aforementioned behaviors might have increased the potential of unapparent exposure to A (H7N9) infected avian and avian-related environment in males. Furthermore, this study demonstrated that the median age of patients with A (H7N9) infection was 56 (range, 1 to 88) years, most cases occurred in the 60-to 79year-old group, and the proportion of fatal cases was higher than nonfatal cases in patients more than 60 years old.…”

Eco-engineering controls vegetation trends in southwest China karst

“…where D represents the environment factors; i  1, 2, All six comprehensive factors are continuous variables, and thus had to be stratified though discretization before they could be used in the GDM (Wang and Xu 2017, Wang and Xu 2017, Wang et al 2010, Ge et al 2017, Wang et al 2017a. In order to avoid subjectivity and randomness in the process of discretization, this study used the natural break classification method, which performs an automatic unsupervised segmentation of the comprehensive factors to receive the breakpoints between the segments (Xu and Zhang 2014).…”

Detection of Infection Sources for Avian Influenza A(H7N9) in Live Poultry Transport Network During the Fifth Wave in China

“…Reason for the distance determination: The Chinese population usually commutes 1 to 3 kilometers in their communities every day [35].…”