Government officials said on Saturday that while the less virulent H5N2 strain found in two farms in central and southern Taiwan cannot harm humans, it could mutate into the more deadly H5N1 strain that has killed four people in Vietnam.

"Taiwan has not been infected by the more severe H5N1 virus up to this point, but we are preparing for battle," said Hu Fu-hsiung, deputy minister of the Council of Agriculture.

South Korea and Japan have also reported cases of the more lethal strain.

The infection at a farm in Chiayi country in the south comes two days after Taiwan reported an outbreak among chickens at a farm in the central country of Changhwa, which is about 100km from Chiayi. 

Officials destroyed 20,000 chicken at the Changhwa farm and have quarantined the area.

"Taiwan has not been infected by the more severe H5N1 virus up to this point, but we are preparing for battle"

Hu Fu-hsiung,
Deputy minister of the
Council of Agriculture

"Up to now, only two chicken farms have tested positive for cases of H5N2. No other areas have reported any cases of infection," said Chiang Yi-nan, director of the Bureau of Animal and Quarantine.

Chiang said farms within a one square kilometre radius of the infected Chiayi farm had been tested. 

Lin Shi-yu, a government animal health researcher, said the viruses at the two farms were identical and strongly suspected the infection could be traced to migratory birds.

"The birds fly across from places such as Japan and Korea and land in the farms and spread the disease," said Lin, who said cross-infection between the two farms could not be ruled out.

The government is stepping up preventative measures by increasing testing nationwide, culling chickens once a case has been discovered and quarantining infected farms, said Lin.

The government is also encouraging farmers to string up nets to prevent migratory birds from landing on their property and possibly spreading the infection.