MADISON, Wis. The emerging H7N9 avian influenza virus responsible for at least 37 deaths in China has qualities that could potentially spark a global outbreak of flu, according to a new study published today (July 10, 2013) in the journal Nature.
An international team led by Yoshihiro Kawaoka of the University of Wisconsin-Madison and the University of Tokyo conducted a comprehensive analysis of two of the first human isolates of the virus from patients in China. Their efforts revealed the H7N9 virus's ability to infect and replicate in several species of mammals, including ferrets and monkeys, and to transmit in ferrets data that suggests H7N9 viruses have the potential to become a worldwide threat to human health.
"H7N9 viruses have several features typically associated with human influenza viruses and therefore possess pandemic potential and need to be monitored closely," says Kawaoka, one of the world's leading experts on avian flu.
Normally, avian influenza viruses do not infect humans, with the exception of the highly pathogenic H5N1 strains. However, the H7N9 virus has so far infected at least 132 humans, killing more than 20 percent of those infected, and several instances of human-to-human infection are suspected.
The new study suggests that the ability of the H7N9 virus to infect and replicate in human cells may be due to just a few amino acid changes in the genetic sequence of the virus. "These two features are necessary, although not sufficient, to cause a pandemic," says Kawaoka, explaining that the influenza virus depends on host cells, which it hijacks to make new virus particles and sustain the chain of infection.
In monkeys, the H7N9 virus was shown to efficiently infect cells in both the upper and lower respiratory tract. Conventional human flu viruses are typically restricted to the upper airway of infected nonhuman primates.
"If H7N9 viruses acquire the ability to transmit ef
|Contact: Yoshihiro Kawaoka|
University of Wisconsin-Madison