Washington Scientists have discovered a new strain of bird flu that appears to sidestep current vaccines.
It's infecting people as well as poultry in Asia, and some researchers fear its evolution may have been steered by the vaccination programs designed to protect poultry from earlier types of the H5N1 flu.
The discovery by Yi Guan of the University of Hong Kong and colleagues is reported in today's issue of Proceedings of the National Academy of Sciences.
The new variant has become the primary version of the bird flu in several provinces of China and has spread to Hong Kong, Laos, Malaysia and Thailand, the researchers report. It is being called H5N1 Fujian-like, to distinguish it from earlier Hong Kong and Vietnam variants.
"We don't know what is driving this," report co-author Dr. Robert G. Webster of St. Jude's Children's Research Hospital in Memphis, Tenn., said in a telephone interview.
New vaccines will have to be developed, Webster said.
While the new virus has infected people, there is no evidence that it can pass easily from person to person, Webster said. However, he added, "this virus is continuing to drift."
Dr. Michael L. Perdue, of the World Health Organization's Global Influenza Program in Zurich, Switzerland, said the new variant doesn't indicate any increased risk for people "other than the fact it seems to be pretty widespread."
Perdue, who was not part of Webster's research team, said WHO is working with the Chinese Ministry of Health to develop a vaccine for the new form of the virus.
The H5N1 flu has devastated poultry in China and several other southeast Asian countries and has claimed more than 150 human lives. Most of the people affected lived close to flocks of poultry.
Health authorities fear the virus will mutate into a form that can spread easily among people, raising the potential for a worldwide pandemic like the one that killed millions in 1918. That worry has spurred efforts to develop vaccines for the virus as well as to test migrating wildfowl in an effort to detect movement of the disease.