Avian H7N9 influenza may be adapting to humans
Masato Tashiro, a scientist with the Influenza Virus Research Center, and Yoshihiro Kawaoka, a scientist with the University of Wisconsin-Madison and the University of Tokyo, collaborated on the study to examine the genetic sequences of H7N9 influenza isolates from four human victims. The group also examined samples from birds and the environment of a market in Shanghai.
"The human isolates, but not the avian and environmental ones, have a protein mutation that allows for efficient growth in human cells and that also allows them to grow at a temperature that corresponds to the upper respiratory tract of humans, which is lower than you find in birds," Kawaoka said.
Avian influenza does not typically infect humans, but it can sometimes adapt to people and pose a major health risk. The findings of the study are troubling and may show that the virus is making adaptations to mammals and humans with the potential to cause a pandemic.
"These viruses possess several characteristic features of mammalian influenza viruses, which likely contribute to their ability to infect humans and raise concerns regarding their pandemic potential," Kawaoka said.
Kawaoka said that most of the viruses from humans and birds displayed mutations in the surface protein hemagglutinin allowing the pathogens to bind to host cells. Once mutated, the viruses were easily able to infect human cells. The human samples showed a different mutation allowing the viruses to thrive and replicate within human cells.
The H7N9 virus has infected at least 33 people so far, killing nine people in total.