Despite working for seven years with indigenous tribes in Brazil that have had no contact with the outside world, the closest Carlos Travassos had ever been to any was earlier this month, when he and his team treated seven Indians for the flu.

Travassos, who is the general coordinator of isolated and recently contacted Indians for the Brazilian government’s indigenous affairs department, FUNAI, had one word for the encounter: “tense.”

Late last month, the group of seven Indians first walked into a village called Simpatia — or ‘Niceness’ — deep in the Brazilian Amazon, near the Peruvian border, in the Kampa Indian reserve in Acre state. The Ashaninka — a so-called contacted tribe because its members have had encounters with outsiders — live there.

There were five men and two women, between the ages of about 13 and 21. All seven caught the flu, a potentially life-threatening illness for them.

Travassos and a multi-disciplinary team got there as quickly as they could.

“It was a difficult situation, a tense situation, and within this situation you could perceive a reaction of distrust,” Travassos said. It wasn’t just the lives of the seven who were in danger; there also was the risk that they could infect the rest of the tribe.

On Friday, Travassos, Brazilian Health Minister Arthur Chioro, FUNAI President Maria Assirati and other specialists met to discuss contingency plans for more potential contacts in the area.

For recently contacted Indian tribes, simple respiratory diseases can be deadly, said Rebecca Spooner, a campaign officer for Survival International, a British non-governmental organization that works to protect indigenous tribes. “It’s very common for half the tribe to be wiped out within a few months of contact,” Spooner said by phone from London.

Just 818,000 of Brazil’s 191 million people are indigenous, according to the most recent census, in 2010. At least 77 groups of uncontacted Indians are believed to be in the Amazon.

Travassos’s team included Douglas Rodrigues, an Indian specialist from the Federal University of São Paulo, and two interpreters.

“We had a doctor who was very experienced,” Travassos said. “We had two very experienced interpreters who knew how to handle this contact.”

The seven were taken to a nearby FUNAI base, treated and kept under observation for five days. Although they arrived naked, almost immediately they put on the odd piece of clothing, Rodrigues said by phone from São Paulo.

The Indians were “curious and frightened,” he said. “They thought they could die. . . . Although their immune system works as well as yours or mine, for them, respiratory illnesses are completely new.”

The Indians asked what ethnic group the team members were from, Travassos said, and had to be reassured that the medicine they were being given was not a spell.

“They told us a little about their social organization, what they planted in their village,” Travassos said. But they expressed the most interest in engines. “They had been watching boats go up and down the river for many years,” he said. “They had observed the helicopter a few times.”

The group members also said they had encountered “white men” previously and described being shot at.

Survival International said the Indians had been fleeing violence on the Peruvian side of the border, a region where drug trafficking and illegal logging are threatening uncontacted tribes and forcing them into Brazil. “There is a huge amount of conflict in the Amazon at the moment,” Spooner said. Oil and gas exploration is also a threat to Peru’s uncontacted tribes, she said.

Thousands of Amazon Indians were killed or enslaved during a rubber boom around the turn of the 20th century. Many have avoided contact ever since. But the desire for trade — even isolated tribes often have machetes or metal pots they have traded with contacted tribes — a change of policy, or even plain curiosity also could have prompted the contact, Travassos said.

The seven Indians have gone back to their village. “They will have a lot of new information, I don’t know what the reaction from the group will be,” he said.

For them, the modern civilization they previously glimpsed at a distance, chugging up an Amazon river on a boat, or flying past in a distant helicopter, has become a reality.

“Pretty much their whole world is turned upside-down,” Spooner said.