Is it possible for a low pathogenic avian influenza strain to become highly pathogenic?
A. Some low pathogenic subtypes have the capacity to mutate into more virulent strains. While low pathogenic avian influenza is considered lower risk, low pathogenic strains of the virus – the H5 and H7 strains – can mutate into highly pathogenic forms. History of Avian Influenza in the United States Q. Does highly pathogenic H5N1 avian influenza currently exist in the United States? Has it ever occurred in this country? A. Incidents of low pathogenic avian influenza are commonly detected in domestic poultry flocks. Low pathogenic avian influenza does not pose a serious threat to human health. There is no evidence that any highly pathogenic avian influenza currently exists in the United States. Historically, there have been three highly pathogenic avian influenza outbreaks in poultry in this country–in 1924, 1983 and 2004. No significant human illness resulted from these outbreaks. The 1924 H7 HPAI outbreak was detected in and contained to East Coast live bird markets. The 1983-84 H5N
