Interventions for avian influenza A (H5N1) risk management in live bird market networks

Abstract

Highly pathogenic avian influenza virus subtype H5N1 is endemic in Asia, with live bird trade as a major disease transmission pathway. A cross-sectional survey was undertaken in northern Vietnam to investigate the structure of the live bird market (LBM) contact network and the implications for virus spread. Based on the movements of traders between LBMs, weighted and directed networks were constructed and used for social network analysis and individual-based modeling. Most LBMs were connected to one another, suggesting that the LBM network may support large-scale disease spread. Because of cross-border trade, it also may promote transboundary virus circulation. However, opportunities for disease control do exist. The implementation of thorough, daily disinfection of the market environment as well as of traders’ vehicles and equipment in only a small number of hubs can disconnect the network dramatically, preventing disease spread. These targeted interventions would be an effective alternative to the current policy of a complete ban of LBMs in some areas. Some LBMs that have been banned still are very active, and they likely have a substantial impact on disease dynamics, exhibiting the highest levels of susceptibility and infectiousness. The number of trader visits to markets, information that can be collected quickly and easily, may be used to identify LBMs suitable for implementing interventions. This would not require prior knowledge of the force of infection, for which laboratory-confirmed surveillance would be necessary. These findings are of particular relevance for policy development in resource-scarce settings.

Avian influenza H5N1 viral and bird migration networks in Asia

“…It has been suggested that the poultry trade, illegal bird trade, and wild bird smuggling may play important roles in the global dispersal of H5N1 (34)(35)(36). Therefore, bird migration networks may not be the only route by which H5N1 is transmitted (17).…”

Connectivity interplays with age in shaping contagion over networks with vital dynamics

“…In other words, if we group the individuals by their number of contacts k, the probability of finding infected individuals is largest in the most represented set. On the contrary, such a probability tends to zero for larger and larger values of k. This means that, contrary to a widespread belief regarding both human (e.g., [6,7,35,36]) and animal diseases (e.g., [37]), the most connected nodes are not necessarily at highest risk of infection when demography is stretching the network topology, even if the original contacts followed a scale-free distribution. This may obviously have implications in the design of effective prevention policies.…”

Les approches écologiques et évolutives incontournables pour mieux comprendre les épidémies de grippe aviaire

“…avec les réseaux formés par les routes de migration permet de retrouver les résultats des analyses phylogénétiques, ce qui n'est pas le cas si l'on considère des réseaux aléatoires. Bien sûr ces routes de migration n'expliquent qu'une partie des épisodes épi-démiques de H5N1 en Chine, et le commerce de volailles est une autre source importante [6,7]. Cependant, ce travail démontre clairement comment l'histoire des migrations d'oiseaux d'eau peut être associée à la propagation du virus H5N1, expliquant ainsi les transmissions sur de longues distances et les réémergences du virus.…”