JAKARTA, Indonesia -- The World Health Organization has detailed the first evidence that a person likely caught the bird flu virus from a human, then passed a slightly mutated version to another person. But scientists said yesterday that the genetic change does not increase the threat of a pandemic.
The investigation said the H5N1 mutation occurred in a 10-year-old Indonesian boy who was part of the largest cluster ever reported. The index case is believed to have been infected by poultry. She then probably passed it to the boy and five other blood relatives.
The boy is then thought to have infected his father, whose samples showed the same mutation, according to the report. Only one infected family member survived.
``It stopped. It was dead end at that point," said Tim Uyeki, an epidemiologist from the US Centers for Disease Control and Prevention.
Uyeki, who was part of the investigating team, stressed that viruses are always slightly changing, and there was no reason for this mutation to raise alarm because the virus has not developed the ability to spread easily among people.
UN bird flu chief David Nabarro said the findings nevertheless emphasized the importance of continuous monitoring of the H5N1 virus in both humans and poultry.
``We were fortunate in that the change that took place did not result in sustained human-to-human transmission," he said yesterday. ``This is a vivid reminder of the need to keep a very close watch on what the virus is doing."
Officials fear the H5N1 virus could eventually mutate into a highly contagious form that spreads easily among people, potentially sparking a global pandemic. The current virus remains hard for people to catch, and most human cases have been traced to contact with sick birds.
Scientists believe limited human-to-human transmission has occurred in a handful of other clusters, all of which involved very close contact.
The WHO report was distributed during a three-day meeting in Jakarta attended by some of the world's top bird flu researchers. Indonesian officials called the closed-door session to ask for help in coping with the virus .
Keiji Fukuda, WHO's coordinator for the Global Influenza Program in Geneva, said the cluster in Indonesia last month drew international attention because of its size. Otherwise, he said, it resembles family clusters elsewhere.
``What we're really looking for is the kind of human-to-human transmission which can cause large neighborhood outbreaks and big community outbreaks," he said. The virus in Sumatra island did not spread beyond the eight blood relatives .