Late last week, Brazil’s Indian affairs department (FUNAI) publicly announced an event that many anthropologists and medical researchers had feared. In the remote Brazilian state of Acre, members of a long-isolated Amazon tribe have contracted influenza after making voluntary contact with the outside world. Some researchers now fear that the contacted individuals, who speak a Panoan language, will spread the potentially fatal virus to other nonimmunized members of their tribe.

Late last month, members of the tribe emerged from the forest along the Upper Envira River in Brazil, raiding the village of another remote but settled tribe, and then contacting members of a FUNAI team and spending up to 3 weeks in their company. Researchers suspect that the newly contacted people were fleeing illegal loggers and cocaine traffickers in part of their home territory in a Peruvian park. Apparently, the tribespeople picked up influenza from this recent contact, according to the FUNAI announcement. Flu virus is potentially deadly to isolated tribespeople because they have no immunity to it, and such transmission is exactly what anthropologists and medical experts hope to avoid during contact. In case after case, contact has proved tragic as diseases like flu and measles decimated previously isolated tribes.

According to the FUNAI announcement, a government medical team treated the newly infected tribespeople and gave them flu immunizations. But the contacted people then slipped back into their forest home—a development that alarms many researchers. “We can only hope that [the FUNAI team members] were able to give out treatment before the sickness was spread to the rest of the tribe in the forest,” says Chris Fagan, executive director at the Upper Amazon Conservancy in Jackson, Wyoming. “Only time will tell if they reacted quickly enough to divert a catastrophic epidemic.”

While FUNAI’s medical officials worked with the tribe, another group of researchers has tentatively identified their culture: The tribe in question may be part of a larger group of Chitonahua people, says Adam Bauer-Goulden, president of the Rainforest Rescue Coalition in Chicago, Illinois. A village of some 40 to 100 tribespeople, believed to be Chitonahua, was photographed from the air in a village along the Xinane River, not far south of the contact area, and the body ornamentation and haircuts of these villagers closely resemble those of the newly contacted group (photo above). Bauer-Goulden thinks the newly contacted folk may come from that exact village. A group of previously contacted Chitonahua now live along the Yurúa River in Peru.

FUNAI noted in the announcement that the newly contacted group said that they had been violently attacked by outsiders. The Xinane River village lies along a major route used by cocaine smugglers, notes Bauer-Goulden, who suspects that “the narcotraffickers pushed them out” of their own lands.

But for now, the immediate worry is disease transmission. It’s possible that the tribespeople picked up other diseases such as malaria during contact. If so, they could conceivably spread the newly acquired pathogens to other members of their tribe. Fiona Watson, research director for Survival International, a nongovernmental organization based in London that seeks to support indigenous tribes, also worries that FUNAI may not have sufficient medical resources on the ground nearby in the event of an epidemic. “There does not seem to be a health team in situ right now,” Watson says. “FUNAI says it will send in a team but only next month.”

It’s a worrisome situation, says anthropologist Robert Walker of the University of Missouri, Columbia. “We are just hearing of one of the many contacts that are going on in this region,” he says. “If you think of how many loggers and narcotraffickers there are in this region, and that there could be as many as 3000 to 4000 uncontacted people there, the potential for contact is huge.”