A team of researchers from the University of Wisconsin-Madison has identified a key step that the H5N1 avian flu virus must take to facilitate its easy transmission from one person to another.
Lead researcher Yoshihiro Kawaoka, a virologist at the UW-Madison School of Veterinary Medicine, has revealed that a single change a viral surface protein enables the H5N1 virus to settle into the upper respiratory system, which "may provide a platform for the adaptation of avian H5N1 viruses to humans and for efficient person-to-person virus transmission."
"The viruses that are in circulation now are much more mammalian-like than the ones circulating in 1997. The viruses that are circulating in Africa and Europe are the ones closest to becoming a human virus," says Kawaoka, an internationally recognized authority on influenza.
The researchers involved two different avian viruses isolated from a single patient—one from the lungs and the other from the upper respiratory system—in the study.
They found that the virus from the upper respiratory system exhibited a single amino acid change in one of the key proteins for amplification of influenza virus genes.
Kawaoka says that such a change promotes better virus replication at lower temperatures, such as those found in the upper respiratory system, and in a wider range of cell types.
"This change is needed, but not sufficient. There are other viral factors needed to cause a viral pandemic" strain of bird flu, he said.
The researchers, however, are convinced that it is only a matter of time, as more humans and other animals are exposed to the virus, before H5N1 virus takes those steps and evolves into a virus capable of causing a pandemic.
The study has been published in the journal Public Library of Science Pathogens.