Seven Indonesian Bird Flu Cases Linked to Patients (Update1)

May 23 (Bloomberg) -- All seven people infected with bird flu in a cluster of Indonesian cases can be linked to other patients, according to disease trackers investigating possible human-to-human transmission of the H5N1 virus.

A team of international experts has been unable to find animals that might have infected the people, the World Health Organization said in a statement today. In one case, a 10-year- old boy who caught the virus from his aunt may have passed it to his father, the first time officials have seen evidence of a three-person chain of infection, an agency spokeswoman said. Six of the seven people have died.

Almost all of the 218 cases of H5N1 infections confirmed by the WHO since late 2003 can be traced to direct contact with sick or dead birds. Strong evidence of human-to-human transmission may prompt the global health agency to convene a panel of experts and consider raising the pandemic alert level, said Maria Cheng, an agency spokeswoman.

``Considering the evidence and the size of the cluster, it's a possibility,'' Cheng said in a telephone interview. ``It depends on what we're dealing with in Indonesia. It's an evolving situation.''

The 32-year-old father in the cluster of cases on the island of Sumatra was ``closely involved in caring for his son, and this contact is considered a possible source of infection,'' The WHO said in its statement. Three others, including the sole survivor in the group, spent a night in a ``small'' room with the boy's aunt, who later died and was buried before health officials could conduct tests for the H5N1 virus.

`Directly Linked'

``All confirmed cases in the cluster can be directly linked to close and prolonged exposure to a patient during a phase of severe illness,'' the WHO said.

While investigators have been unable to rule out human-to- human transmission in the Sumatran cluster, they continue to search for other explanations for how the infections arose, the WHO statement said.

Health experts are concerned that if H5N1 gains the ability to spread easily among people, it may set off a lethal global outbreak of flu. While some flu pandemics are relatively mild, the 1918 Spanish flu pandemic killed an estimated 50 million people worldwide.

So far, studies of the Sumatran outbreak and genetic analyses of the virus don't indicate the virus has undergone major changes, Cheng said. Scientists at WHO-affiliated labs in the U.S. and Hong Kong found no evidence that the Indonesian strain of H5N1 has gained genes from pigs or humans that might change its power or spreading ability, WHO said.

Mutations

``These viruses mutate all the time and it's difficult to know what the mutations mean,'' Cheng said.

Health officials earlier found strong evidence of direct human-to-human spread of H5N1 in Thailand in 2004. Scientists reported in the Jan. 27, 2005, issue of the New England Journal of Medicine that the H5N1 virus probably spread from an 11-year- old girl in Thailand to her aunt and mother, killing the mother and daughter. People who had more casual contact with the girl didn't become infected.

In the Sumatran cluster, close, direct contact with a severely ill person was also needed for spread, Cheng said. Preliminary findings from the investigation indicate that the woman who died, considered to be the initial case, was coughing frequently while the three others spent the night in the same room. One of the three, a second brother, is the sole survivor. The other two, her sons, died.

``It looks like the same behavior pattern'' of close contact and caretaking during illness with the bird flu virus, Cheng said. To raise the level of pandemic alert ``it would have to be transmissible from more casual contact.''

General Community

The Indonesian Ministry of Health and international scientists are continuing their investigation to trace the origins of the infections, the WHO said in its statement.

``Priority is now being given to the search for additional cases of influenza-like illness in other family members, close contacts, and the general community,'' the WHO said. ``To date, the investigation has found no evidence of spread within the general community and no evidence that efficient human-to-human transmission has occurred.''

To contact the reporter on this story:
John Lauerman in Boston at  jlauerman@bloomberg.net.

Last Updated: May 23, 2006 14:46 EDT