Associations between attributes of live poultry trade and HPAI H5N1 outbreaks: a descriptive and network analysis study in northern Vietnam

Our results indicate that LPT's trading for less than a year and operating at retail markets are more likely to source poultry from flocks located in communes with a past history of HPAI H5N1 outbreaks during 2003 to 2006 than LPT's trading longer than a year and operating at wholesale markets. The results of the network analysis indicate that LPT's tend to link communes of similar infection status.Our study provides evidence which can be used for informing policies aimed at encouraging more biosecure practices of LPT's operating at authorised LBM's. The results suggest that LPT's play a role in HPAI H5N1 transmission and may contribute to perpetuating HPAI H5N1 virus circulation amongst certain groups of communes. The impact of current disease prevention and control interventions could be enhanced by disseminating information about outbreak risk and the implementation of a formal data recording scheme at LBM's for all incoming and outgoing LPT's.The recurrence of poultry outbreaks of highly pathogenic avian influenza of the H5N1 subtype (HPAI H5N1) in some parts of the world, and the occasional spillover of infection to humans, is a significant global health concern. Poultry rearing is an important enterprise in countries across the greater Mekong region. In Vietnam, poultry rearing is closely linked with people's livelihoods and traditional culture [1,2].Five epidemic waves of HPAI H5N1 occurred in Vietnam between late 2003 and mid-2008, causing the second highest human case incidence and case-fatality rates in the world. The proximity of poultry flocks to water courses and paddy fields, and keeping of other poultry species all have an important role in sustaining and perpetuating infection [3-7]. Poultry outbreaks are primarily reported in the Red and Mekong river deltas, and the majority of outbreaks are recorded in the predominant small-holder chicken and duck flocks. Agro-ecological factors related to poultry husbandry, trade and social-cultural customs are su