BEIJING, Jan. 21 -- The race against bird flu is a race against evolution.

    Epidemologists are now working to develop a vaccine against the killer disease before the strain mutates into one that can be carried -and trasmitted- by humans.

    That could likely happen if the virus lodges itself in a pig - an animal with an immune system similar to ours- or if the virus combines itself with a strain of human influenza.

    As the H5N1 strain kills more people the stakes grow higher.

    An 18-year-old girl died of bird flu in southern Viet Nam and the first confirmed human infection in the country's north has raised concerns about possible human-to-human transmission of the virus.

    The girl died in a Ho Chi Minh City hospital on Wednesday after battling the highly virulent H5N1 strain for nearly two weeks since she was hospitalised on January 6 in the southern province of Tien Giang, the Tuoi Tre (Youth) newspaper said.

    Her death took the Asian bird flu death toll to 38 - 26 in Viet Nam and 12 in Thailand.

    Thailand has declared a state of emergency while seven Vietnamese people have been confirmed as infected by bird flu.

    The latest confirmed case of H5N1 infection was a 42-year-old man in the capital, Hanoi, which has raised fears the virus could jump from person to person, state-run Vietnam Television said late on Wednesday.

    It said the man had had no contact with sick poultry but that he went to take care of his older brother in a Hanoi hospital earlier this month.

    The older man died of a respiratory illness on January 9, although tests showed he did not have bird flu.

    "The Ministry of Health is conducting epidemiological investigations into these cases and the UN's World Health Organization (WHO) will keep in close contact with the Ministry of Health over the progress and findings of these investigations," WHO said in a statement on its Web site (www.who.int).

    "They were having contact with each other," Hans Troedsson, Viet Nam representative of the UN health agency. "Before we can make any conclusion if it would be a human-to-human transmission, we need to investigate much more."

    Troedsson said there would probably be isolated cases of human-to-human transmission, but this did not necessarily spell disaster.

    "Human-to-human transmission might not be anything new because we know there was one similar situation in Thailand last year where it could have been a human-to-human transmission," he said.

    Troedsson said another suspected human-to-human case occurred in 1997 in Hong Kong. That year, the H5N1 strain caused severe respiratory illness in 18 people, of whom six died, marking the first instance of direct bird-to-human transmission of bird flu.

    If a cluster of infections started to emerge, it might be regarded as evidence of human-to-human transmission, he said.

    What the WHO fears most is that the virus could mutate if it got into an animal capable of hosting a human flu virus.

    That would probably be a pig, and if the H5N1 were to merge with a human flu virus, it could produce a strain capable of sweeping through a human population without immunity, the WHO says.

    Millions could die worldwide.

    "We have no evidence that the virus has mutated or changed. That is the good news. The pattern is similar to last year," Troedsson said.

    The H5N1 virus already kills a high proportion of the people it infects.

    More human deaths are feared. The WHO said in Geneva on Tuesday it had been told by Viet Nam that up to 10 more suspected human cases were under investigation.

    Four are in Hanoi, two of them in critical condition and on a respirator.

    "There is not yet any evidence of human-to-human transmission," he said, but added that the latest confirmed infection in Hanoi had prompted experts to "more in-depth investigations."

    No vaccines yet exist to help humans fight the H5N1 virus, he said.

(Source: China Daily)