The World Health Organization has confirmed a fifth person in Vietnam has died after contracting (感染）a bird flu that has been wiping out chicken farms throughout Asia.

After receiving results from Vietnam's ministry of health, WHO spokesman Bob Dietz told The Associated Press on Monday that an 8-year-old girl from Ha Tay province had died from the H5N1 virus.

The girl first showed symptoms on January 11 and was admitted to a Hanoi hospital on the 15th. She died two days later.

So far, the H5N1 strain of bird flu has been confirmed in five cases. All of those patients have died. Vietnam has reported at least 18 suspected cases.

Health officials believe the infected patients contracted the disease through contact with the sick birds' droppings, and young children are particularly vulnerable.

"We are working on the scenario （情景，场面）that these children are playing around in the backyard where chickens are present and out in the streets, " WHO spokesman for the Western Pacific region, Peter Cordingly, told CNN last week.

"Often in the suburbs of Hanoi, chickens roam （游荡，闲逛）wild and they may have come in contact that way ... That is quite clearly an avenue of investigation we should start with."

High fever, coughs, low blood pressure and low levels of blood cells are all symptoms of the disease.

Bird flu has infected millions of chickens in Vietnam, South Korea and Japan, prompting those nations to order huge slaughters at poultry farms.

Vietnam on Friday decided to ban the sale of all poultry in Ho Chi Minh City, the nation's largest city.

Beijing has halted poultry imports from the three affected countries, following similar measures by Hong Kong and Cambodia earlier in the week.

While there is no evidence of human to human transmission or any documented cases of infection through eating poultry products, the WHO fears the disease may latch on to a normal human influenza virus.

If this occurs, the WHO has said the flu could prove to be a bigger problem than SARS.

Some two million chickens have died or been slaughtered in Vietnam because of the disease. The virus also has infected chickens in South Korea and Japan.

In Japan, about 30,000 chickens will be culled （挑出而杀掉）and last month over one million chickens and ducks died or were slaughtered in South Korea after an outbreak of the bird flu.

The first documented cases of bird flu affecting humans was in Hong Kong in 1997 when six people died. Over one million poultry animals were culled at that time.