¬†A study led by St. Jude Children’s Research Hospital scientists found the avian influenza A H3N8 virus that killed harbor seals along the New England coast can spread through respiratory droplets and poses a threat to humans. The research appears in the current issue of the scientific journal¬†Nature Communications.

The avian H3N8 virus was isolated by scientists investigating the 2011 deaths of more than 160 harbor seals. Researchers discovered the virus had naturally acquired mutations in a key protein that previous laboratory research had shown allowed the highly pathogenic avian H5N1 virus to spread though respiratory droplets. Scientists reported that the avian H3N8 seal virus infected and grew in human lung cells. Researchers also found that the virus spread in ferrets though respiratory transmission, which is uncommon for avian flu viruses and raises concerns about possible person-to-person airborne spread of the harbor seal virus. Investigators found no evidence of human immunity to the strain.

“This study highlights a gain-of-function experiment that occurred in nature and shows us there are avian flu viruses out there beyond H5N1 and H7N9 that could pose a threat to humans,” said corresponding author Stacey Schultz-Cherry, Ph.D., a member of the St. Jude Department of Infectious Diseases. In recent years, human cases of highly pathogenic avian H5N1 and H7N9 flu have been confirmed in countries around the world, with mortality rates approaching 60 percent.