Don't panic on bird flu, says U.N.
Workers at Hong Kong's bird garden take precautions.
Nations hit by bird flu
Taiwan (different strain)
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ROME, Italy -- The United Nations is warning against panic in countries suffering an outbreak of bird flu.
Health experts are meeting in Rome for a three-day summit to develop a unified strategy for combating the virus, which has now claimed 13 human lives.
A six-year-old boy became the fourth person to die of the disease in Thailand, while Vietnam has reported nine fatalities.
Thai officials are awaiting test results on 18 suspected cases, 11 of which have already died. So far all of the country's confirmed cases of the illness have succumbed to it.
The government on Tuesday said 102 people with flu-like symptoms are being "examined closely" -- up from 81 a day earlier. They have yet to be moved into the suspected case category.
The virus also appears to be spreading in China. The country now has newly confirmed or suspected cases reported in six provinces.
Beijing also confirmed the H5N1 virus, which is the more deadly strain of bird flu, has struck chickens in the southern province of Guangdong.
No human has contracted the virus in China, according to government officials.
"It's very important we remain calm about worst-case scenarios," The Associated Press quoted Mike Ryan, head of the global epidemic response network at the World Health Organization (WHO), as saying.
"What we're dealing with is small clusters of cases associated with exposure to poultry. We have a strain of influenza with the potential to pick up human genes, and we're nowhere close to declaring a pandemic."
Ten Asian countries are battling bird flu, also known as avian influenza, and at least 45 million chickens have been slaughtered across the region to stop its spread.
Cases in humans have been reported only in Vietnam and Thailand, with most traced to direct contact with sick birds.
Fears the disease had spread to Europe subsided after doctors said a German tourist who came down with flu-like symptoms after visiting Thailand was most likely free of the disease.
Investigators have been unable to trace the infections of two Vietnamese women to contact with chickens and have not ruled out human-to-human transmission.
Even if the women did catch the disease from a family member, limited transmission of the virus between people is not the real danger.
Experts fear the virus mutating into a form that passes easily between people -- a pandemic strain that is a hybrid of the bird virus and a human influenza.
Joseph Domenech, chief of the FAO animal health department, addressed the concern the virus could mutate.
"Today we are not at this stage, but animal outbreaks are multiplying," he said.
"It's still an increasing curve, so if it continues that way, the risks are still more and more."
At least 25 international experts from 15 countries are attending the Rome meeting, including high-level veterinary officials from affected nations and representatives of the U.S. Centers for Disease Control and Prevention.
Health officials say destroying infected birds, if safely carried out, is the best way to contain the disease.
People who eat poultry are not at risk from bird flu but import restrictions on live birds are needed to stop the disease spreading, experts say.
The European Union and Japan have barred poultry products from Thailand.
The EU extended its ban Tuesday for another six months, applying it to Cambodia, Indonesia, Japan, Laos, Pakistan, China, South Korea, Thailand and Vietnam.
WHO also is spearheading the hunt for a bird flu vaccine.
Ryan said prototypes developed by the agency will shortly be supplied to pharmaceutical companies so they can begin research on a usable vaccine, which experts expect to be ready within months.
-- CNN Bangkok Bureau Chief Tom Mintier and The Associated Press contributed to this story.