The number of Vietnam's confirmed bird flu deaths has risen by one to four, the World Health Organisation said, while a hospital in the country's south said today it had two very sick patients with bird flu symptoms.
Five children remain hospitalised in Hanoi as suspected avian flu cases, but only one is very sick, Mr Peter Horby, WHO epidemiologist, told Reuters Television in an interview.
He said another seven adults suspected of having bird flu were being treated at Hanoi's Bach Mai hospital, but added it was difficult to assess the number of cases as the disease had symptoms similar to other ailments.
"It's not easy to distinguish it from any other severe respiratory disease," Mr Horby said.
South Korea, Japan and Taiwan have also reported outbreaks of bird flu but Vietnam has been the hardest hit.
The cases have raised fears of a new deadly epidemic sweeping out of the region that saw an outbreak of Severe Acute Respiratory Syndrome spread around the world last year and kill about 800 people.
All of Vietnam's confirmed cases, plus eight other human flu deaths under investigation, were from the north. But a hospital in the southern province of Kien Giang said it was treating a woman and man, both in their twenties, for serious influenza infection with symptoms similar to the avian flu victims.
Vietnam has reported 18 suspected cases of bird flu in humans with 12 deaths suspected of being linked to it.
The type of avian flu virus that caused the four confirmed bird flu deaths is similar to a variant that struck Hong Kong in 1997, killing six people.
But the WHO said it had found no evidence of human-to-human transmission of the H5N1 virus.
There had been an increase in respiratory cases in Hanoi's hospitals but they had not been proven to be bird flu, the WHO said.