Live Poultry Exposures, Hong Kong and Hanoi, 2006

Since 1997, the largest epidemic of highly pathogenic avian influenza (H5N1) ever recorded has caused 172 human and several billion bird deaths. Recently administered questionnaires determined that live poultry exposures have declined by ≈63% in Hong Kong since 2004 and that, in Vietnam, domestic backyard exposures to poultry are likely more important than retail exposures.

M ost human cases of highly pathogenic avian infl uenza H5N1 (HPAI) arise from exposure to infected poultry (1-3; Figure). Mapping poultry exposure and its determinants can enhance HPAI surveillance (4). We compared live poultry exposures in both Hong Kong Special Administrative Region and Vietnam in 2006 and examined changes in levels of exposure in Hong Kong since 2004, when a similar survey was performed in Hong Kong (4).

The Study
In Hong Kong, random household telephone interviewing of 1 adult >17 years of age selected by Kisch grid (which randomizes selection of persons within households) was conducted from December 2005 through 2006 from a list of 5,000 numbers. Simultaneously in Vietnam, stratifi ed cluster sampling was carried out throughout 2 districts in each of 5 northern provinces. Within 3 of these provinces, 1 district with and 1 without an HPAI epidemic history were selected. Within each district, 1 urban and 1 rural commune each provided 100 households randomly selected from electoral rolls. Kisch grid selected 1 adult from each household for face-to-face interviews.
Respondents estimated their live poultry purchase frequency and touching at purchase (4). We attributed standard values to respondents' reports (e.g., monthly = 12; weekly = 52) (4) to give standardized household purchases of live poultry. Multiplying standard purchases by reported buying frequencies standardized buying patterns (4). Selfreported buyer touching of birds during purchase was standardized by adjustment for reporting differences by gender proportion weighting (4) and reported touching frequency to calculate adjusted buying exposures. Vietnam also surveyed backyard poultry practices. Households raising poultry reported the number, type, changes in husbandry practices, and poultry deaths for the past 12 months.

Conclusions
In Hong Kong, 2,784 contacts yielded 1,760 interviews (return rate 63%); 64% of respondents were women and 36% were men; their median age, 44 years (  (Table 2). Households kept a median of 9 chickens. Overall, 22% of those keeping backyard poultry reportedly had birds die in the previous year. Of these, 12% of households threw the dead bird away without informing authorities, 9% informed the authorities, and 5% sold or ate the dead bird. Of those reporting bird deaths, 214 (84%) had been ordered by offi cials to destroy some or all of their birds. Incidence of bird deaths was greater in rural areas (52% vs. 48%, Fisher p<0.001), but rural residents threw them away (68% vs. 32%, Fisher p = 0.031) or sold or ate them (87% vs. 13%, Fisher p = 0.006) more often than did urban residents.
In Hong Kong, government import restrictions have reduced poultry availability by 41% from 2004 to 2006. Purchase and touching declines prompted by health education messages have together reduced exposure by ≈60%.
Fewer Vietnamese households bought live chickens, but those that did so bought at comparable frequencies to Hong Kong 2006 households. Chickens are relatively more expensive in Vietnam. Adjusted for purchasing power parity (www.worldbank.org/data/quickreference/quickref. html), live chickens costs $16.6-$18.0 and $21.8-$31.0 (international dollars; www.worldbank.org/data/quickreference/quickref.html) each in Hong Kong and in Vietnam, respectively. Hence, temptation to use sick, dying, or dead poultry is high, increasing the risk for human infl uenza (H5N1) infection (7). Average Vietnamese exposure range from backyard sources (28-194 exposures/person/year) is 100-700× higher than Hong Kong 2006 exposures from purchasing (0.23 exposures/household/year). If 53% of Vietnamese households average 9 birds each and if 22% of these households (2,129,582) had only 1 bird die, a 5% consumption rate of the dead birds means that 106,500 sick or dying birds are consumed annually, posing a major health threat (7). This is a risk that governments must urgently target.
Limitations include generalizing from 5 northern Vietnamese provinces to the country as a whole and using arbitrary estimates for backyard exposure frequency. Nonetheless, valuable data are presented on differential exposure patterns.