Researchers Develop New Method For Assessing Influenza Pandemic Potential

08/01/06

Researchers at the Centers for Disease Control and Prevention (CDC) have developed a new research method that may help identify the types of genetic changes necessary for the avian influenza virus (H5N1) to be more easily transmitted among people.

After developing the research method, CDC scientists used it to investigate the ability of a lab-engineered combination of the avian influenza virus and a more common human virus to spread in lab animals. Efficient and sustained human-to-human transmission is the remaining property that H5N1 avian influenza viruses do not yet have that is needed to cause a pandemic.

In this series of experiments, published in the July 31 issue of the journal Proceedings of the National Academy of Sciences, genes from a human H3N2 influenza virus were added to genes from an H5N1 avian influenza virus to create new hybrid viruses. The new viruses were tested in ferrets because their susceptibility to flu viruses is similar to that of humans. The animals were then placed in close proximity, to see if infected ferrets passed the new virus to uninfected animals and whether they transmitted it more easily than the original H5N1 virus.

In this model, human H3N2 viruses transmitted efficiently between the ferrets, but avian H5N1 viruses did not. When the hybrid viruses were tested it was found that these viruses also did not pass easily between ferrets.

“This important science has established a new research method to help us learn more—in advance—about the genetic changes that enable new influenza viruses to spread efficiently and in a continuous manner among people,” says CDC Director Julie Gerberding, MD. “H5N1 viruses continue to spread among birds worldwide and their genetic properties are constantly changing. There is an urgent need to better understand how these viruses could acquire the ability to spread efficiently between people. This research increases our knowledge, and may enable us to more quickly identify H5N1 viruses and other influenza viruses that have the potential to cause a pandemic.”