The avian flu has killed millions of chickens in South Korea, Vietnam and Japan, where officials have ordered mass culls to try to contain the outbreak. Hong Kong and Cambodia have banned poultry imports from countries affected by the bird flu.
WHO says tests are being conducted to determine if the deaths of six additional people in Vietnam are linked to the disease, but has stressed that there has been no person-to-person spread of the disease.
Health officials attribute infections in humans to contact with the feces of sick birds.
If the virus develops the ability to spread through human contact, it could become a big health crisis, WHO regional coordinator Peter Cordingley said Wednesday in Manila, Philippines.
It's "a bigger potential problem than SARS because we don't have any defenses against the disease," Cordingley said. "If it latches on to a human influenza virus, then it could cause serious international damage."
The bird flu scare comes just as China grapples with new cases of severe acute respiratory syndrome, another ailment believed to have originated in animals and which ravaged the region's economy in a major outbreak last year.
China last week confirmed its first SARS case of the season, and has since announced two additional suspected cases, all in southern Guangdong province, next to Hong Kong.
The bird flu's symptoms in humans include fever and coughing and eventual pneumonia — similar to SARS.
The three avian flu deaths in Vietnam — an adult and two children — were confirmed Tuesday as Influenza A or the H5N1 strain, the same virus found in sick chickens in the country's south, WHO said. The same strain of bird flu killed six people in Hong Kong in 1997, when more than 1 million chickens and ducks were culled.
Health officials say they believe there is no danger from eating properly cooked meat or the eggs of affected chickens. Still, governments and businesses in the region sought to bolster consumer confidence in their poultry industries.
"There is no case reported of humans infected by taking chicken meat or eggs," Japanese Agriculture Minister Yoshiyuki Kamei said. "Therefore, I wish for the citizens of Japan to react in a calm manner on this issue."
Japanese officials said 10,000 chickens had died from the bird flu and thousands of others would be slaughtered.
The disease is spreading fast among poultry in Vietnam, where more than 1 million chickens have died in the latest outbreak. Farmers have been ordered to destroy all sick birds.
An official at Ho Chi Minh City's only crematorium said the facility has been running at full capacity, 24 hours a day, over the past few days, incinerating more than 2 tons of dead chickens a day.
Thailand, among the world's largest poultry exporters, declared itself free of bird flu.
An outbreak starting last month in South Korea led to the slaughter of 1.1 million chickens and ducks in an attempt to contain the disease.