U.N. experts sought to dampen fears Friday that bird flu (search) had spread to another species after tests found the virus in the snouts of pigs in Vietnam. Two more people died of the disease, bringing the human death toll to 18.
The U.N. Food and Agriculture Organization (search) said the results do not necessarily mean the pigs are infected. The tests -- nasal swabs -- may merely be confirming the presence of infected chicken droppings on their snouts. Swine are often housed with poultry in traditional family farms in Asia.
Rigorous tests look for the virus or antibodies in the blood, the agency said.
Even if the pigs were infected, that would still not be cause for alarm, said Peter Roeder, a veterinary virologist and animal health expert at FAO headquarters in Rome. Experts have known for years that pigs can get bird flu.
"The issue is whether they are important in the propagation and transmission of this epidemic," Roeder said. "There's absolutely no evidence that this is so at the moment."
"Let's not be alarmist. Let's just deal with things as they evolve," he said.
A Vietnam representative of the U.N. Food and Agriculture Organization announced the test results early Friday in Hanoi.
Bird flu has ravaged poultry farms across Asia and is continuing to spread. More than 50 million chickens have been slaughtered to stem the spread of the disease. Ten governments are battling outbreaks.
China was investigating mysterious reports of finches dropping dead from the sky, and villagers in Indonesia sprinkled thousands of birds with holy water and then set them ablaze as they tried to rid the resort island of Bali of the deadly disease.
Vietnam announced the deaths of a 6-year-old girl from southern Dong Nai (search) province and a 24-year-old man from central Lam Dong (search) province, raising the total in that country to 13. Five people have died from the virus in Thailand.
Most human cases have been traced to direct contact with infected chickens. However, experts have said it's possible the virus can jump to humans through another mammal, such as pigs.
"Right now, there is no justification for saying there is H5N1 (search) virus infection in pigs in Vietnam," Roeder said, referring to the lethal strain of avian influenza plaguing poultry across Asia.
Experts say that despite a handful of human infections, there is no sign that the virus is changing into one that could spread widely among people. However, they are watching it closely.
There are two ways the virus could become a danger to humans.
It could gradually accumulate enough genetic mutations to become efficient at spreading among humans, or -- more rapidly -- it could combine with a normal human flu strain and create a potent hybrid that has the deadliness of the bird strain and the contagiousness of a regular human flu strain.
Properly cooked chicken meat or eggs is not dangerous because the virus is killed by heat, but governments worldwide have slapped affected countries with bans on imports ranging from live poultry -- a disease risk -- to cooked poultry products -- which experts say pose no risk.
Vietnam this week banned all poultry sales.
Governments fighting the scourge are Thailand, China, Vietnam, Laos, Cambodia, Indonesia, Japan, South Korea, Pakistan and Taiwan. The strain afflicting Pakistan and Taiwan, however, is milder and not considered dangerous to humans.