Responses to Threat of Influenza A(H7N9) and Support for Live Poultry Markets, Hong Kong, 2013

Peng Wu, Vicky J. Fang, Qiuyan Liao, Diane M.W. Ng, Joseph T. Wu, Gabriel M. Leung, Richard Fielding, and Benjamin J. Cowling

Author affiliations: School of Public Health, The University of Hong Kong, Hong Kong, China

Abstract

We conducted a population survey in Hong Kong to gauge psychological and behavioral responses to the threat of influenza A(H7N9) and support for closure of live poultry markets. We found low anxiety and low levels of exposure to live poultry but mixed support for permanent closure of the markets.

A novel influenza A(H7N9) virus was detected in China in March 2013, and an epidemic of infections in poultry and humans occurred during April and May of that year (1,2). Most persons who had laboratory-confirmed infections reported recent contact with live poultry, and evidence suggests that human-to-human transmissibility of the virus is low (2). Incidence of laboratory-confirmed human cases dramatically decreased following the closure of live poultry markets (LPMs) in affected cities in April 2013 (3). Control of the virus is challenging because its low pathogenicity in poultry (4) requires reliance on laboratory-based surveillance in animals or humans to identify areas where the virus is prevalent and to facilitate interventions to reduce human exposure to infected poultry.

Hong Kong imports live poultry from mainland China only from a few dedicated farms that have adequate biosecurity protection; intensive surveillance for avian influenza is conducted at the border and within Hong Kong. Risk for influenza A(H7N9) virus infection appears to be low in Hong Kong, but 4 infections have been reported in Hong Kong residents since December 2013, and a surge in influenza virus transmission was anticipated in eastern China this winter (2). Prevention and control activities rely on accurate measures of exposure to live poultry, risk perception and psychological and behavioral responses related to the virus, and attitudes toward specific control measures. We therefore conducted a series of cross-sectional population surveys to monitor these variables in Hong Kong.

The Study

We initiated the first survey in April 2013 (April 10–13 and 25–27), shortly after the first human case of influenza A(H7N9) was announced in mainland China. A second survey was conducted December 4–8, after incidence of human cases began to rise in the winter and the first local infection occurred in Hong Kong. We used methods and survey instruments similar to those used for surveys during the severe acute respiratory syndrome epidemic in 2003 (5), the influenza A(H1N1)pdm09 pandemic (6), and the emergence of avian influenza A(H5N1) (7).

For the survey, trained interviewers made telephone calls to land lines by using a computerized, random-digit dialing system; calls were placed during nonworking hours and weekends to avoid overrepresentation of nonworking groups. Within households, adults >18 years of age who spoke Cantonese were eligible and were randomly selected on the basis of a Kish grid (8). Up to 4 follow-up calls were made if participants were not available or if calls were unanswered. Verbal informed consent was obtained from all participants. Means and proportions of survey items were directly weighted by sex and age to the general population, and multiple imputation with 10 datasets was used to correct for missing data.