A team of scientists at the U.S. Centers for Disease Control and Prevention (CDC) have developed a new research method that may help identify the types of genetic changes that would be necessary for the avian influenza virus (H5N1) to be more easily transmitted among people.
At present bird flu fortunately does not appear to have an efficient and sustained human-to-human transmission property that is needed to cause a pandemic; but viruses can evolve into epidemic and pandemic forms by mixing their genetic material with other viruses.
The scientists used the new process to find out how a lab-engineered combination of the avian influenza virus and a more common human virus would spread in laboratory animals.
They wanted to understand the genetic changes that are needed for an H5N1 virus to acquire the genetic changes needed to cause a pandemic.
CDC scientists designed and tested a research method that involved three elements: ferrets; a caging system that enabled researchers to put healthy and infected animals in close proximity; and reverse genetics, a tool for combining the genes from human and avian influenza viruses.
The team mixed genes from a human H3N2 influenza virus to genes from an H5N1 avian influenza virus in order to create new hybrid viruses.
Infected ferrets were either placed in the same cage with uninfected ferrets to test transmissibility by close contact or in adjacent cages with perforated walls to test spread of the virus by respiratory droplets.
Dr. Jackie Katz one of the lead researchers at the CDC's Influenza Branch says the work was carried out in high-security labs to eliminate any risk to the public.
The human H3N2 viruses transmitted efficiently between the ferrets, but avian H5N1 viruses did not and when the hybrid viruses were tested it was found that these viruses also did not pass easily between ferrets.
Julie Gerberding CDC Director says the findings are a concern because the data does not mean that H5N1 cannot convert to be transmitted from person to person, but rather suggests that it is a complex process.
According to Gerberding there are more than 50 possible combinations of the viruses, and Katz and her team could have created a dangerous strain of flu.
The H5N1 virus remains essentially a disease of birds which is quite difficult for humans to contract and usually entails contact with sick or infected birds.