Public Health Risk from the Avian H5N1 Influenza Epidemic

Abstract

Repeated transmission of the avian H5N1 influenza virus to humans during the ongoing avian epidemic has raised concerns that such events might initiate a global pandemic of a highly pathogenic human virus. We review the current global mechanisms of influenza surveillance, and highlight the need for improved surveillance of animal viruses. We show how risk assessment and surveillance can be enhanced by quantitative analysis, and emphasize that low-level human-to-human transmission is not necessarily indicative of an emerging pandemic. We propose that the appearance of uncharacteristically large clusters of cases is indicative of increased viral transmissibility and hence of when to issue global alerts and implement stringent control measures.