Bird Flu Alarm



Understanding Avian Influenza

Low Pathogenic versus Highly Pathogenic Avian Influenza Viruses


H5 and H7 subtypes of avian influenza A viruses can be further classified as either highly pathogenic avian influenza (HPAI) or low pathogenic avian influenza (LPAI). This distinction is made on the basis of genetic features of the virus. HPAI is usually associated with high mortality in poultry. It is not certain how the distinction between "low pathogenic" and "highly pathogenic" is related to the risk of disease in people. HPAI viruses can kill 90 to 100% of infected chickens, whereas LPAI viruses cause less severe or no illness if they infect chickens. Because LPAI viruses can evolve into HPAI viruses, outbreaks of H5 and H7 LPAI are closely monitored by animal health officials.

Understanding Avian Influenza