Rogue bird flu resistant to vaccines

Oct 31 2006

Researchers in Hong Kong and the U.S. say a new strain of the H5N1 bird flu virus has emerged in China and what is more of a worry is the strain appears to be resistant to vaccines.

The new strain called the "Fujian-like virus" because it was first isolated in China's southern Fujian province in March 2005, is spreading through southeast Asia, and has become dominant throughout the region, replacing other variants of the virus.

Dr. Yi Guan, director of the State Key Laboratory of Emerging Diseases at the University of Hong Kong says the implications are that current control measures are ineffective in dealing with the evolutionary changes that H5N1 undergoes.

Dr. Yi Guan, lead author of a new report, says they believe the virus has already instigated a third wave of H5N1 infection in the region, and is already widespread in southern China.

It has already caused poultry outbreaks in Laos, Malaysia and Thailand, and human disease in Thailand.

Dr. Yi Guan says the new strain's dominance is because it was not as easily affected as other strains by the avian vaccine initially used to prevent H5 infection and this shows that H5 avian vaccines are not able to prevent infection by this virus as efficiently as they do with other strains of H5N1.

The Hong Kong team say the new strain was also responsible for recent human infections of the avian flu virus in both rural and urban areas of China, and such human infections could lead to a serious outbreak, which would challenge current plans aimed at preventing a human pandemic.

Guan says the immediate danger is to flocks of chickens and other poultry, and their study suggests that reliance on a single vaccine against H5N1 over a number of years, which is the current practice, is unlikely to adequately control the disease in poultry.

He says the methods of poultry vaccination must be addressed.

The researchers say although China has a compulsory program of chicken vaccination, the new strain evades that program and there is a very real fear that it could spread to infect poultry throughout Asia and Europe, and perhaps jump to infect humans.

Guan says increased systematic influenza surveillance in poultry over the affected regions is the most important thing that can be done at present and the strains of bird flu virus used in poultry vaccines should be assessed regularly and changed if necessary.

The first wave of H5N1 outbreaks occurred in late 2003 and 2004 in many parts of Asia.

The second wave started in China's Qinghai Lake in May 2005 and that strain has since been found in parts of Europe, Africa and the Middle East.

To date the virus has killed more than 150 people since late 2003 but remains largely a disease among birds.

But experts fear it could trigger a flu pandemic and kill millions of people if it mutates into a strain that can pass from human to human.

The researchers are from the University of Hong Kong, and include virologists Guan Yi and Malik Peiris, and Rob Webster of St. Jude Children's Research Hospital in the United States; their study appears in the current issue of the Proceedings of the National Academy of Sciences.