BioEd Online

Reports that a 26-year-old Vietnamese male nurse has tested positive for bird flu have added to concerns that the virus may gain the ability to pass between humans. But health officials have yet to determine exactly how the man contracted the illness.

Researchers have linked most human cases of bird flu to direct contact with sick poultry. But they fear that the virus will, or already has, mutated such that it can be transmitted from person to person. Of nine bird-flu cases among family members recorded since 2003, officials have found it very difficult to rule out human-to-human transmission in two cases.

The World Health Organization (WHO) has not yet verified the reported illness of the nurse in Vietnam. But on 7 March 2005 it did confirm four new cases of bird flu in that country, including one death. According to WHO spokesman Dick Thompson, the organization is working for heightened surveillance and rapid investigation of new cases.

"We've been worried since we first identified avian influenza in the environment," he says.

A Vietnamese health official stated that the nurse had been caring for a 21-year-old man in a Hanoi hospital who caught the virus after drinking raw duck blood, a local delicacy. The patient and his 14-year-old sister, who came into contact with sick poultry and has also caught bird flu, lived in the northern province of Thai Binh.

Causes for concern

The nurse may have become infected as a result of the particularly close contact he had with the patient. "He may well have been infected but this is not the norm. It doesn't necessarily mean that this is the beginning of a new pandemic," cautions Karl Nicholson, a professor of infectious diseases who is working on a bird flu vaccine at the University of Leicester, UK.

Nicholson explains that the H5N1 bird flu virus would need to recombine with a human virus in order to create a pandemic in the near future.

The H5N1 virus first made the jump from poultry to people in 1997 in Hong Kong. Five years later the virus, which had evolved subtly, caused an outbreak that began in Thailand. Based on the current recognized cases of the illness, it seems to have an 80% mortality rate, says Nicholson.

Medical experts have noted that in Vietnam most of the recent cases of bird flu have involved children and young adults. They are also concerned that the country's scientific infrastructure is insufficient to properly monitor the problem.