Scientists in Vietnam are concerned that the deadly bird flu may have infected two more people, and they suspect the virus may have mutated into a more dangerous form which could spread in mammals, and cause outbreaks in poultry.
According to the media there a student is being tested in hospital after eating chicken eggs along with samples from a 78-year-old woman who died from serious pneumonia in the central province of Quang Binh on Friday.
The two cases now bring to four the human suspects in Vietnam, with the other people now being treated at a hospital in the northern province of Bac Giang.
According to a report by the Agriculture Ministry, the H5N1 virus has now hit 10 of Vietnam's 64 provinces, including Bac Giang, since re-surfacing there in early October.
Vietnam's death toll since the virus first arrived there in late 2003 is 42.
In the latest affected area in the northern port of Haiphong, 1,000 ducks and chickens have already died on four farms.
Bui Quang Anh, head of the ministry's animal health department, said in an urgent message to provincial authorities, that there is possibility that the disease is spreading due to improper quarantine of infected poultry and poultry products.
He wants to deploy search-and-destroy task force groups to deal with sick poultry.
Apparently the Ho Chi Minh Pasteur Institute has decoded genetic material from 24 samples of the H5N1 virus taken from poultry and humans.
The institute says that the H5N1 type that infected people and waterfowl in early 2005 has several mutations focusing in the important functional parts of the surface proteins, on its Web site, it refers to protein receptors on the surface of the ball-like virus that allow it to enter and exit an animal cell.
It says there has been a mutation allowing the virus to replicate effectively in mammal tissue and become highly virulent.
The study also found a mutation of the PB2 gene in a virus sample from a patient who died in southern Dong Thap province earlier this year.
It appears that the virus had been combining changes to adapt to new hosts.