St. Jude Children's Research Hospital said on Tuesday that successors of the H2N2 avian influenza A virus from the 1950s are still a threat.
The study of H2N2 avian influenza used samples of the virus collected from domestic poultry and wild aquatic birds between 1961 and 2008. Research showed the virus was able to infect human respiratory cells. Researchers classified one virus as a high-risk for pandemic.
The researchers also determined the viruses responded to antiviral medications and could potentially be controlled by an available vaccine.
"This study suggests H2N2 has the characteristics necessary to re-emerge as a significant threat to human health in part because most individuals under the age of 50 lack immunity to the virus," Robert Webster, a member of the St. Jude Department of Infectious Diseases, said. "This highlights the importance of continued surveillance of viruses circulating in animals and additional research to enhance our ability to identify viruses that are emerging health threats."
Researchers were able to study the viruses by infecting ferrets, which are susceptible to the same viruses as humans. They tested five out of nine viruses using the ferrets, and were able to determine which viruses are high-risk for triggering a pandemic and which are low-risk.
"While these viruses genetically look very avian, this study shows they can behave like mammalian viruses and replicate in multiple mammalian models of flu," Jeremy Jones, the study's first author and postdoctoral fellow in Webster's laboratory, said. "That is troubling because some of the original H2N2 pandemic viruses looked avian when the pandemic began in 1957, but in a few short months, all of the isolated viruses had picked up the genetic signatures of adaptation to humans. Our results suggest the same could happen if the H2N2 viruses again crossed from birds into humans."
Researchers at St. Jude continue to study changes in avian flu viruses and their ability to infect humans.