A trader transports chickens on the back of his motorbike on a road near Hanoi, Vietnam (file photo)

Authorities in Vietnam say four members of a family have been hospitalized with symptoms of bird flu, in the country's first suspected cases of the disease in more than a year.

Officials say the mother and her three children, aged between three and 13 years old, fell ill after eating a sick chicken earlier this month in Ca Mau province. Health officials say they are being tested for the deadly H5N1 strain of the virus.

Earlier this month, Vietnam reported its first bird flu outbreaks in poultry in a year in Ca Mau and two other provinces in the Mekong Delta. The outbreaks killed or forced the slaughter of thousands of poultry there.

Vietnam has the second highest number of human bird flu deaths after Indonesia. More than 150 people have died from the disease, mainly in Asia.

Most of the deaths happened as a result of contact with sick birds, but experts fear the virus could mutate into a form that easily transmits by human-to-human contact.

Some information for this report was provided by AP and Reuters.