May 4, 2006

 

Bird flu expert urges more studies on bird flu transmission
 

 

A leading flu expert warned the scientific community on Wednesday (May 3) against blaming the spread of the deadly H5N1 virus on wild migratory birds, saying more studies should be done on the role of poultry and its movement around the world.

 

People often overlook the movement involved in the huge industrial scale of poultry farming, said Kennedy Shortridge, who spent three decades studying flu viruses, at a bird flu conference in Singapore.

 

Shortridge's assertions run contrary to the expert opinions in this field, who have attributed the recent spread of the H5N1 worldwide to wild migratory birds from China's Qinghai Lake.

 

An outbreak of the H5N1 virus in Qinghai Lake  last May killed thousands of birds and that particular strain of the virus has since been found in Europe, Africa and the Middle East.

 

However, Shortridge challenged the theory, saying that birds usually fly north-south and not east-west.

 

He also said the spread of the virus beyond Qinghai Lake may not necessarily be due to wild birds as the route of transmission did not follow regular migratory routes but instead followed the Trans-Siberian railway.

 

Shortridge also noted there's movement of poultry from one country to another, even to Nigeria ,where there is bird flu and smuggling of poultry.

 

Water can also be a link in the chain of transmission, said Hiroshi Kida of the department of diseases control at Japan's Hokkaido University.

 

The H5N1 can be preserved in frozen lakes and ponds and transmitted by wild birds through many short-haul flights which culminated in the spread of disease to areas as far as Europe and Africa.

 

At the same time, nearly 150 different strains of the virus with the potential to cause a global pandemic were laying in wait, Kida warned.

 

Kida said H5N1 virus -- responsible for 113 deaths around the world -- was one of at least 144 potential different strains which posed a threat to humans.

 

All the strains were present in ducks, which act as carriers often without showing any flu symptoms, he said.

 

Bird flu viruses are a threat to humans because humans have no natural immunity against most of them and because they can jump from birds to people. One strain in 1918, caused a pandemic in which an estimated 50 million people died, he said.

 

Virologist Malik Peiris told the conference the assumption that H5N1 would wear itself out may be wrong.

 

During past pandemics, flu viruses quickly evolved but wore themselves out and killed only a small percentage of people.