The WHO has dispatched a team of investigators to the area, including experts from the organization's headquarters in Geneva, but they have been unable to find any evidence of contaminated poultry in the village that may have triggered the human infections. "If we can't find an external source that explains all seven confirmed cases, then we have to go with the theory that this is human-to-human," says Peter Cordingley, the spokesperson for the WHO's Western Pacific regional headquarters. Human-to-human transmission within a family is believed to have occurred at least twice before, in Thailand and Vietnam, although never involving this many people. But if the 10-year-old boy was infected by a family member, and then went on to infect his father, it would represent the first known time the virus had passed from human to human to human. "It's certainly possible," says Gregory Hartl, a WHO spokesperson in Geneva.
That's a worrying threshold to cross, but the good news is that the virus doesn't seem to have spread outside the family. The 32-year-old man ran away from doctors after falling ill, and passed though four neighboring villages before he was apprehended, coming into contact with 33 people. All of them are currently under observation and being given the antiviral drug Tamiflu as a prophylactic, but none have shown signs of infection. Scientists have genetically sequenced two viruses isolated from the cluster and found no evidence of the kinds of significant mutations that would likely be necessary before the virus could pass easily from person to person. "The virus looks pretty much the same as other cases," says Dr. Guan Yi, an avian-flu expert at the University of Hong Kong who has seen the genetic sequences.
If those contacts remain healthy for the next week and a half, then the outbreak at Kubu Sembilang will likely be judged contained. But the cluster itself could remain a mystery. Villagers have been extremely uncooperative with investigators, complicating efforts to get samples from animals and forcing the WHO to set up its command hub 5 miles from the village. "We don't have a lot of access to the village right now," says Hartl. "But they've lost seven people. There's a lot of shock and grief they have to work through first." It's a reminder of the power bird flu still has to surpriseand to kill.