Thailand faces the threat of new HIV subtypes, particularly one stemming from the locally common subtype E merged with the foreign subtype C, which is believed to cause the disease to spread wider and faster, experts said yesterday.

"It's feared that the new virus could even trigger a new, major HIV epidemic in the country," said Professor Ruengpung Sutthent, the head of Siriraj Hospital's Department of Microbiology.

The National HIV Repository and Bioinformatic Centre, which monitors genetic changes in the virus, detected this new form of HIV in a random test last year, said Ruengpung, who is also director of the centre.

The centre regularly carries out tests to see whether the virus has undergone any significant alteration in its genetic makeup and last year found subtype C in a combination with subtype E for the first time in the country, Ruengpung said.

"The finding gives us a warning that it (the worst-feared HIV subtype C) is coming," she said.

The new E-C subtype accounted for 0.5 per cent of a total of 201 HIV samples, said Ruengpung, adding that most such infections were in eastern provinces like Rayong and Chonburi.

Subtype C is in more than half of the world's HIV patients and commonly found in Africa, she said, adding that the virus had migrated from the continent to spread across India, China and Burma. It had made its presence felt all over the world before coming to Thailand, said Ruengpung, adding that this subtype was commonly found in heterosexuals and spread faster than any others studied so far.

A John Hopkins University article published last year showed that HIV's "recombinant subtypes" hinted at the possibility of a rapid spread of the disease, said Prof Prasert Thongcharoen, the country's leading virologist.

He said there were already about 20 recombinant subtypes, which could make matters worse due to a faster spread of the virus. As elsewhere in the world, HIV subtypes in Thailand are increasingly and alarmingly getting mixed with one another, with the deadliest threat being posed by subtype C.

Reupung said that, apart from experts' concerns about subtype C's ability to spread fast, its combination with other subtypes raised fears of increased resistance to drugs and about the ongoing HIV vaccine trials.

The world's largest HIV vaccine trials being conducted in Thailand covered only the E and B subtypes, she said.

"Since people are travelling, the best way to prevent further mixings of the subtypes is to practise safe sex," said Dr Winai Ratanasuwan, an assistant professor in Siriraj's Department of Preventive and Social Medi-cine.

Still, the subtype B, commonly found in gay men diagnosed with HIV, had shown a significant genetic change, said Ruengpung. In fact, she said, this form of subtype B was usually found in the US and EU.

This, she said, coincided with the US Centres for Disease Control finding of a higher rate of HIV infection among Thai men who have sex with men.

"The new form of subtype B in Thai gay men may have spread from their counterparts in either America or Europe," she said.

The doctor insisted however that this subtype B was not the one that made headlines in New York City last year when a gay man died only a couple of years after contracting a form of HIV which resisted all available life-saving antiretroviral drugs.

Arthit Khwankhom

The Nation