WEDNESDAY, May 24, 2006 (HealthDay News) -- A cluster of bird flu deaths in an Indonesian family has international health officials worried that the virulent virus might have managed to mutate so it can spread freely among humans. However, infectious disease experts stress this latest development is not cause for public panic.
As of Wednesday, the World Health Organization (WHO) said it was leaving its pandemic alert level unchanged; it's currently at a level where there is "no or very limited human-to-human transmission."
The agency is also investigating whether the Indonesian strain was spread among seven relatives living in northern Sumatra island, six of whom have died. One of the victims -- a 32-year-old man -- died after catching the infection as he tended to his ill 10-year-old son, who eventually died from the illness. The boy is thought to have caught the infection from his aunt. If confirmed, that would be the first recorded case of three-person transmission of H5N1, experts said.
However, so far, WHO officials say there is no evidence at this point that the virus had mutated. An eighth relative was buried before tests could be conducted, but she is also considered to have been infected with the H5N1 strain of bird flu.
Tracking the outbreak, top epidemiologists -- including two experts from WHO's global headquarters in Geneva and the Centers for Disease Control and Prevention in Atlanta, are on the scene in Sumatra, identifying people who had contact with the most recent victim and checking for any signs of sickness.
Meanwhile, experts in this country said Wednesday there's little cause for concern at this point.
"There's no evidence that the current spread among this family cluster in Indonesia represents a major mutation to the H5N1 virus," said Dr. Marc Siegel, author of Bird Flu: Everything You Need to Know About the Next Pandemic and clinical associate professor of medicine at New York University School of Medicine in New York City. "I prefer the CSI approach, to rampant speculation."
Experts generally agreed that major genetic changes would need to take place in the H5N1 strain of bird flu before it could spread easily from human to human. Such changes do not appear to have occurred in this instance.
And there's still the possibility that an infected bird that might have triggered the outbreak simply hasn't been identified yet.
"The first person they think got infected more than two weeks ago, and was buried, and probably any sick birds are dead and buried, too," added Dr. Susan McLellan, an associate professor of medicine at Tulane University School of Medicine in New Orleans. "We know that bird flu is in Indonesia. I don't think it's a great mystery. I think she was probably another person who contracted the flu from a bird."
But since officials cannot find the source of the infection, it raises the possibility that the virus was spread from human to human, rather than from bird to human. This, in turn, raises the specter that the virus is finding it easier to jump between humans, possibly leading to a pandemic.
So far, bird flu has killed 124 people in 10 countries, most of them in Vietnam and Indonesia. This is out of 218 documented human cases in the same 10 countries. More than 200 million domestic fowl have been killed worldwide to help stem the spread of the illness.
Human casualties remain largely confined to Asia, and among people who have had close and prolonged contact with infected birds, such as poultry farm workers.
Nevertheless, there have been isolated cases of human-to-human transmission, all of them between family members, according to the New York Times.
"The big question is, where did they get the virus from?" Siegel said. "If they passed it to each other, which hasn't been proven, I think it's absolutely likely that it's a high inoculum [amount of virus]. If you took a load and dumped it into someone's lungs, they're going to get sick."
According to Siegel, coughing and sneezing do not seem to be enough to spread the virus from human to human, because the virus needs to land in the lungs. If one family member were tending to a sick relative, contact might be close enough to be dangerous. And the first woman to contract the virus also hosted a pig roast for several guests while she was sick.
"Clearly, she was coughing ... and people were staying in her very small habitation, so there was really close contact," McLellan said.
One boy who was exposed to the original sick woman did then spread the disease to his father, a troubling case of secondary transmission. Again, however, the transmission occurred in extremely close quarters, McClellan said.
And experts have not ruled out the possibility that people became infected from food the original woman prepared, or that the woman was somehow able to spread the virus more efficiently. Those are real considerations, McLellan said.
"It's certainly not something to ignore because if, in fact, there are some people who find a way to spread this better than others or if there's an unrecognized means like contaminated food products, we need to know about that," he said.
Officials also need to learn if the virus is becoming more acclimated to human hosts even without a major genetic shift, Siegel added.
However, the full details might never be known.
"More information is needed about what's going and authorities will probably have difficulty fully explaining one way or the other," said Dr. Gordon Dickinson, chief of infectious diseases at the University of Miami School of Medicine. "We may be left only knowing that this is a possible cluster related to human-to-human transmission."
More information
For more on bird flu, visit the U.S. Centers for Disease Control and Prevention.
