Chulalongkorn University has found that a virus sample from Nakhon Phanom province in the Northeast was of a strain newly observed in Thailand and more closely related to H5N1 strains that have been circulating since 2005 in southeast China.

In contrast, H5N1 samples from Phichit province in the lower North region were similar to the cluster of samples isolated during 2004 and 2005 outbreaks in Thailand and Vietnam, said Professor Yong Poovorawan, author of the Chulalongkorn University study.

The viruses isolated from Phichit belonged to genotype Z, whereas the virus isolated from Nakhon Phanom belonged to genotype V, he wrote in his report.

The latest bird-flu outbreak, in the Northeast province of Mukdahan, has raised concerns that the genotype V virus from the Northeast could spread to meet with the genotype Z virus endemic in the lower North and Central region, said veterinarian Rakthai Ngampak, head of the Department of Livestock Development's Bird Flu Control Centre. Although the results of DNA sequencing of the virus samples taken from Mukdahan are yet to be known, it is very likely that they are the same strain found in Nakhon Phanom, given the way the virus killed poultry, Rakthai said.

Yong and Rakthai agreed that the consequences of a new strain of H5N1 emerging from the mixing of the two genotypes might or might not be serious.

However, Professor Pilaipan Puthavathana, a virologist at Mahidol University's Siriraj Hospital, said: "It won't be good if the two genotypes meet and mix.

"That will create an extraordinary virus with unknown and unpredictable dangers," she said.

Scientists would have to start studying the new virus from scratch, though the existing vaccine could work well against the new strain, Pilaipan said.

Rakthai said various measures were needed for blocking the spread of the Northeast strain to other regions, particularly the Central region. Bird-flu screening measures carried out during past outbreaks did manage to intercept certain infected poultry, he added.

However, there are other ways the virus could spread besides infected poultry, including migratory birds, he said.

"Since we cannot control the migratory birds, what could be done is keep the poultry away [from them] in closed farms," he said.

The problem is a lot of poultry is raised outdoors, including free-range ducks, backyard chickens and fighting cocks, Rakthai said.

As a result active laboratory surveillance is very important to provide warning signs of the two genotypes getting mixed, said Yong.

Arthit Khwankhom

The Nation