The World Health Organization said there was "appropriate alarm" each time the virus, particularly the virulent H5N1 strain, shows up in a new country. But it was important to keep the risk to humans in perspective, WHO spokesman Dick Thompson said.

"People confuse it with pandemic influenza, but they're very different diseases," Thompson said. "If people just paid attention to the human risk" from bird flu, they'd understand that "the possibility of infection is very low."

Health officials have been tracking the strain out of concern that it could mutate into a form more easily transmitted between people, and trigger a human pandemic.

At the moment, however, the flu is principally a bird disease. H5N1 has killed about 60 people in Asia, but they were mostly poultry farmers infected directly by birds.

"The spread of H5N1 to poultry in new areas is of concern as it increases opportunities for further human cases to occur," a WHO statement said. "However, all evidence to date indicates that the H5N1 virus does not spread easily from birds to infect humans."

People with fever or respiratory symptoms should be checked because the early symptoms of H5N1 infection mimic those of many other common respiratory illnesses, WHO said. "False alarms are likely."

In Turkey, the H5N1 strain was detected after 1,800 turkeys died on a farm in Kiziksa, 80 miles southwest of Istanbul, but the Turkish government said it has contained the outbreak.

In Romania, authorities have identified a few cases of bird flu, but established only it was the H5 subtype. Further testing was under way to determine the strain.