Human-to-human spread of bird flu detailed

JAKARTA, Indonesia — The World Health Organization (WHO) has detailed the first evidence that a person likely caught the bird-flu virus from a human and passed a slightly mutated version to another person. But experts said Friday the genetic change does not increase the threat of a pandemic.

The investigation said the mutation of the H5N1 strain of the virus occurred in a 10-year-old Indonesian boy on Sumatra island who was part of the largest cluster ever reported.

The initial human case is thought to have been infected by poultry. She then likely passed it to the boy and four blood relatives. The boy is then thought to have infected his father, whose samples showed the same mutation, according to the report obtained by The Associated Press.

Only one infected family member survived.

"It stopped. It was [a] dead end at that point," said Tim Uyeki, an epidemiologist from the U.S. Centers for Disease Control and Prevention (CDC).

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.

The first five relatives were infected with identical strains of H5N1, as the bird-flu strain is known. But the virus mutated in the 10-year-old. He passed the mutated virus to his father, WHO spokesman Dick Thompson said.

That mutation allowed an Indonesian lab to match the strains that infected father and son, he said.

The father died about four weeks ago, he said. But soon after he was infected, roughly 50 people he had come into contact with were identified and closely observed for three weeks. None developed bird-flu symptoms, Thompson said.

U.N. bird-flu chief David Nabarro said the findings emphasized the importance of continuous monitoring of the H5N1 virus in humans and poultry.

"This is a vivid reminder of the need to keep a very close watch on what the virus is doing," he said by telephone Friday.

Experts fear the H5N1 virus could 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 think limited human-to-human transmission has occurred in a handful of other clusters, all of which involved very close contact.

Health experts said the fact bird flu kills more than half its victims makes the prospect of a pandemic particularly frightening.

The virus has killed at least 130 people worldwide since it began ravaging Asian poultry stocks in late 2003.

Material from The Baltimore Sun is included in this report.