Review of the epidemiological studies of H5N1 influenza virus from both animal and human health perspectives

Abstract

Background: Highly Pathogenic Avian Influenza A virus subtype H5N1 has been reported of significant global health concern with the recurrences of poultry outbreaks of H5N1 in some parts of the world, and the occasional spill over of infection to humans. In Vietnam, there had been five epidemic waves of H5N1 with the second highest human case incidence and case-fatality rate in the world. Ecohealth and One Health approaches have been initially recommended as strategies for controlling and prevention of infectious diseases including H5N1 at the national level. The objective of this paper is to critically review epidemiological studies of H5N1 influenza A virus (H5N1) infection in both humans and animals in Vietnam. Methods: Published literature and reports, outlining epidemiological studies of H5N1in Vietnam, over the period 2003 - 2011 and performed by researchers with both veterinary public health perspective and human health perspective, were reviewed. Results: Although Avian Influenza viruses such as H5N1 circulating in animals pose threats to human health and increasingly are present in multi-strain mixed gene pool presentations and circulating among multiple hosts including humans, epidemiological studies of H5N1 from veterinary public health perspective were much more numerous than those from a human health perspective. This was true with respect to the scale of study as well as the comprehensiveness of the study i.e. consideration of key epidemiological components (e.g., full outbreak investigation, tracing, use of vaccination, spatial temporal analysis, modelling, and impact of social and social networks). Most studies considered either the health of either humans or animals. A few studies referred to and/or made linkages between human health and animal health. However, no joint efforts were identified that fully explored and validated the epidemiology of the animal and human interface of H5N1. Conclusion: Given the significant threats and potential impacts of H5N1 in both humans and animals, epidemiological studies should be extended to explore the animal and human interface of disease. An ecohealth approach would be useful to target not only humans but also poultry and other animals in epidemiological studies of H5N1 as well as other infectious diseases.