The first human bird flu case was tracked down in Myanmar.
A 7-year-old girl from Shan state in the east of the country fell ill with fever and headache in November, and subsequently tested positive for the potentially deadly H5N1 strain of the disease, WHO said in a Web statement.
The girl has since recovered. Samples were tested at a national laboratory in Yangon before being confirmed by a WHO-associated laboratory in Japan.
An outbreak of H5N1 in poultry was reported in Shan state around the time the girl was infected, and WHO is now investigating how the girl fell ill. To date, all of the people who came into contact with the girl remain healthy, WHO reported.
Experts believe most human victims of the virus are infected through direct contact with sick birds. Although bird flu is difficult for humans to catch, experts fear it could mutate into a form that spreads easily among people and spark a flu pandemic.
Myanmar is the 13th country to report cases of H5N1 in humans, WHO said.
A total of 339 people have been infected with the virus since 2003, resulting in 208 deaths, according to the U.N. health agency.
Bird flu cases typically spike in the winter, as the virus survives longer at lower temperatures. Pakistan was also investigating its first suspected human H5N1 cases this week.
Health officials worry that in countries with weak surveillance systems, spotting early bird flu cases could be difficult, giving the virus a chance to spread undetected.