A 4-year-old Vietnamese boy who died after developing severe diarrhea and falling comatose had bird flu, even though he didn´t have breathing problems or other typical symptoms, according to research in the Feb. 17 New England Journal of Medicine.

The deaths of the boy and his 9-year-old sister after a similar illness show the infection may manifest in a variety of ways, and may be more widespread than previously thought, according to researchers in Oxford University´s clinical research unit at Hospital for Tropical Diseases in Ho Chi Minh City. The children´s February 2004 deaths had initially been attributed to acute encephalitis of unknown origin.

The avian influenza virus called H5N1 has killed as many as 32 Vietnamese, 12 Thais and one Cambodian since the end of 2003, with three more Vietnamese deaths still to be confirmed, according to the World Health Organization.

``Clinical surveillance of influenza H5N1 should focus not only on respiratory illness, but also on clusters of unexplained deaths or severe illnesses of any kind,´´ Menno de Jong, a virology researcher who led the study, wrote with colleagues. ``These cases have important clinical, scientific and public health implications.´´

Scientists investigated samples taken from the boy´s body over a nine-month period before they reached their diagnosis. The boy had been admitted to a local hospital five days before his death with a diagnosis of septicemia, a blood infection, and then transferred to the Hospital for Tropical Diseases. His symptoms included fever, vomiting, headache and severe diarrhea.

Influenza Pandemic

The boy´s sister had died on Feb. 2, 2004, a day after being admitted to the local hospital with gastrointestinal symptoms and getting a similar diagnosis. There were no tissue or blood samples from the girl for the researchers to later evaluate to confirm her cause of death. They suspect it was caused by the same virus, according to the study.

There haven´t been reports that the disease can be transmitted person-to-person. Still, bird flu may spread beyond of Asia unless global efforts to fight it step up, the United Nations said earlier today before a regional conference in Vietnam. A situation in which the virus mutates to better infect humans could resemble the 1918 influenza pandemic that probably killed 40 million people, the UN´s health agency said last month.

The fact the virus was found in stool samples from the boy ``is a major source of concern,´´ the researchers wrote. ``It highlights a potential route of human-to-human transmission, especially in combination with crowded living conditions and diarrhea.´´

A study of the children´s home village after the final diagnosis in November didn´t find other cases of the illness among either humans or poultry. More than 1.8 million poultry have died or been culled in Vietnam since the beginning of December to stop the H5N1 virus from spreading further.