Avian influenza A H7 viruses normally circulate amongst avian populations with some variants known to cause infections in humans but this is an uncommon occurrence, though there have been confirmed infections in people who have direct contact with infected birds. At the moment person-to-person infections do happen but only in cases where there was close, prolonged and intensive contact between patients.
|[Foto: China Navis]|
In another interesting aspect of the study, the researchers experimentally infected pigs. Pigs are susceptible to influenza viruses. And because they can be infected with both bird and human flu strains, they are thought to play a key role in the formation of new hybrid strains.
The researchers also noted that pigs could become infected with the Influenza A(H7N9) virus, but didn’t pass the virus from infected animal to healthy animal. What this data would suggest is that it is unlikely that this virus came from pigs.
Ron Fouchier, a Dutch virologist, commented that “This virus is already well on its way. … It is poorly transmissible, but it can transmit. So there are reasons to date to take this virus seriously.”
 Zhu et al: Infectivity, Transmission, and Pathology of Human H7N9 Influenza in Ferrets and Pigs in Science - 2013