The U.N. health agency on Tuesday raised to 160 its official tally of people worldwide who have been infected with the deadly H5N1 strain of bird flu virus after laboratory tests in London confirmed that at least 12 people in Turkey have been infected with the disease.

The death toll from the disease has risen to 85, including four in Turkey, the World Health Organization said on its Web site.

Nine further samples, from individuals confirmed by Turkish health officials as H5N1 positive, are still being examined in Britain to verify that they carried the disease, said WHO spokesman Iain Simpson.

The agency does not officially update its tally of confirmed cases until the disease has been verified in a laboratory outside the country of the outbreak, meaning that WHO's figures often lag behind national counts.

H5N1 has ravaged poultry stocks across Asia since late 2003 and spread to birds in eastern Europe and the Middle East. Experts fear the virus could mutate into a form that passes easily between people, possibly sparking a human pandemic.

All human cases had been restricted to eastern Asia until the first positive test results for the virus in Turkey earlier this year.

On Monday, Iraqi officials announced that a 15-year-old girl who died Jan. 17 had contracted bird flu — the first human case in that country.

Simpson said WHO was sending a team to northern Iraq to investigate possible bird flu cases. They are expected to arrive from the agency's office in Amman, Jordan, on Wednesday