Study says H7N9 could spark global flu outbreak
An international research team by Yoshihiro Kawaoka of the University of Wisconsin at Madison and the University of Tokyo analyzed two of the first human isolates of the virus from patients in China. Kawaoka's team determined that the H7N9 virus' ability to infect mammals and transmit in ferrets suggests the viruses could become a worldwide human threat.
"H7N9 viruses have several features typically associated with human influenza viruses and therefore possess pandemic potential and need to be monitored closely," Kawaoka said.
The study suggests the H7N9 virus is able to infect and replicate in human cells because of a few amino acid changes in its genetic sequence.
"These two features are necessary, although not sufficient, to cause a pandemic," Kawaoka said. "If H7N9 viruses acquire the ability to transmit efficiently from person to person, a worldwide outbreak is almost certain since humans lack protective immune responses to these types of viruses."
Kawaoka's team found that one of the H7N9 strains transmitted between mammals via respiratory droplets. Most avian flu viruses lack the ability to transmit through the air.
Another complication is that the H7N9 virus does not kill poultry, which makes disease surveillance difficult.
"We cannot simply watch out for sick or dead birds," Kawaoka said. "Rather, tests have to be performed to determine whether or not a bird is infected. Considering the vast number of poultry, this is a daunting task."
Kawaoka said further research is needed to support the development of vaccines, assess the risks of infection and better understand why H7N9 viruses are so efficient at infecting humans.