A Vietnamese couple and their three children have been infected by Asia’s bird flu in the latest human cases of the deadly virus that has killed 49 people since the end of 2003, state media reported on Tuesday.

The five, from a district where bird flu had killed poultry, were sent to hospital in the northern port of Haiphong last week suffering fevers and breathing problems.

Preliminary tests on the 39-year-old man, his wife and their three daughters - between 4 months and 10 years - confirmed they had the H5N1 variant of the virus, the Lao Dong newspaper reported.

Doctors and officials could not be reached for comment, but the newspaper said the family had eaten sick chickens after more than half of their 400 birds died earlier this month.

Bird flu swept across the region in early 2003 and has killed 35 people in Vietnam, 13 of them since late December when the disease broke out anew in the southern Mekong Delta. It has spread to more than one third of Vietnam’s 64 provinces.

The virus, which has also claimed 12 Thais and two Cambodians, has killed about 70 percent of the people known to have been infected, but it does not pass easily from bird to humans and eating infected fowl cooked properly is not dangerous.

Experts fear that if the virus could mutate into a more contagious form and jump between humans, it could unleash an influenza pandemic and that millions could die.