The World Health Organization (WHO) said Friday there is not enough evidence so far to prove that the bird flu virus infects pigs.

WHO spokeswoman Fadela Chaib made the statement in response to the Food and Agriculture Organization's (FAO) announcement of detecting H5N1, the most infectious bird flu virus, in several pigs in Vietnam.

Dick Thompson, a spokesman for WHO's communicable diseases division, said FAO's conclusion is preliminary and it is too early to make a final conclusion.

Earlier on Friday, an official of the FAO, Anton Rychener, said pigs in and around Vietnam's capital city of Hanoi tested positive for the H5N1 virus.

The finding is alarming because pigs, whose immune system is similar to that in humans, can become a "mixing vessel" for the flu virus and then infect people.

The bird flu has rapidly spread across half of the Asian continent in 10 countries or regions and claimed 18 deaths since last December.

(Xinhua News Agency February 7, 2004)