November 1, 2006

 

New strain of bird flu may spark third wave of infections worldwide

 

 

A new strain of the H5N1 bird flu virus has been found in poultry in southern China, spreading new fears of human and poultry infections.

 

If confirmed, this could lead to the start of a third wave of bird flu infections, according to a report in the Proceedings of the National Academy of Sciences released Tuesday (30 October).

 

The first wave of H5N1 outbreaks occurred in late 2003 and spread to many parts of Asia. The second wave began in China's Qinhai Lake in May 2005 and spread to Europe, Africa and the Middle East.

 

The new strain, called Fujian-like because it was first identified in Fujian province in May 2005, became the dominant strain in southern China early this year. It has already spread among poultry in Hong Kong, Laos, Malaysia and Thailand.

 

The strain may have become resistant to vaccines, and China's vaccination programme may even have backfired and made it stronger, the researchers said.

 

The researchers tested poultry in markets in six southern Chinese provinces  between July 2005 and June 2006.

 

2.4 percent of the poultry were tested positive for H5N1, an increase of 1.5 per cent from the previous year.

 

The increase in virus activity among poultry and is likely to be caused by the Fujian-like virus, researchers said.

 

The Fujian-like virus is astonishingly dominant. The strain was only present in 3 percent of H5N1-positive samples collected between July and September 2005. Samples collected between April-June 2006 indicated a 95 percent presence.

 

Guan Yi, a virologist and professor of microbiology at the University of Hong Kong who led the research, said that the new strain is unlikely to have been caused by viral mutation but is probably an unidentified strain that has become more dominant thanks to vaccination.

 

Current vaccines are unable to prevent infection by this virus, Guan added.

 

Since virus strains can achieve dominance in a short time, vaccines used against certain strains should be updated on a regular basis, Guan said.

 

However, Zheng Shijun, of Beijing-based China Agricultural University, called for more tests before jumping to conclusions.

 

Since there have been no massive outbreaks since the strain emerged, it is possible that poultry could have strong natural resistance to this new viral strain, Zheng said.