Hanoi - Vietnamese authorities believe a woman who died last week may have been infected with avian influenza, state media said Monday.

The state-run newspaper Vietnam News reported the 26-year-old woman was admitted to a hospital in Soc Trang Province, in the country's Mekong Delta, on March 16 with symptoms of headache, high fever and respiratory difficulties.

Her condition worsened and she died on Friday.

The head of the community health centre where the patient was initially treated reportedly said she had eaten a sick duck about a month ago.

Tests are to confirm later this week whether the woman was infected with the H5N1 avian flu virus.

Bird flu has struck eleven provinces in Vietnam this year, killing tens of thousands of domestic fowl.

So far, there have been four confirmed human cases of bird flu, three of whom have died. In 2008, six people contracted bird flu, five of them did not survive.

Nguyen Huy Nga, the director of the Ministry of Health's Preventive Medicine department, was quoted in the Gia Dinh & Xa Hoi newspaper as saying that all bird flu deaths occurred due to late hospital admission.

Bird flu is usually spread by contact between infected birds and humans, but scientists fear that the virus could mutate into a form that is easily transmissible among humans and spark a global pandemic that could kill millions. (dpa)