The woman, from a district of the capital, Hanoi, is the latest bird flu patient detected in northern Vietnam, where fewer outbreaks have been reported in recent weeks, but where cool spring weather still favours the spread of the H5N1 virus.

A laboratory researcher said tests on the other patient, the 14-year-old girl, also confirmed she had the virus that had also infected her 21-year-old brother.

"The girl also has the virus," said the researcher at Hanoi's National Institute of Hygiene and Epidemiology which conducts bird flu tests.

Her brother has been in critical condition and on a respirator after a traditional drink of duck blood before the Lunar New Year festival last month, officials said.

The siblings and a 36-year-old infected man are from the northern province of Thai Binh, 110 km (70 miles) southeast of Hanoi and far from the southern Mekong Delta where the outbreaks began in December.

Officials said the H5N1 virus killed a 69-year-old man last week in Thai Binh, taking the toll to 14 people in Vietnam since December and the total to 47 since the virus erupted across large parts of Asia at the end of 2003.

Almost all the victims -- 34 Vietnamese, 12 Thais and a Cambodian -- have caught it directly from poultry.

The Agriculture Ministry said poultry infections occured this year only on small farms.

It has ordered a halt until June 30 to the hatching and raising of waterfowl such as ducks and geese, which experts said can carry the virus without showing symptoms.