Update 27/03/2020: The indigenous Marubo man suspected of having a COVID-19 infection has tested negative for the disease, Mongabay reports. There are still no confirmed cases among indigenous people in Brazil.

It's feared that a number of indigenous people in Brazil’s Javari Valley have been infected with COVID-19 after having contact with a group of American tourists.

At least three Marubo indigenous people, including an adult man and two children, have fallen sick with symptoms of fever, cough, and body aches in Atalaia do Norte, western Amazonas state.

State health authorities told Amazônia Real they suspect the cases might be COVID-19. However, there is no laboratory in the area to confirm the cases or not, so their samples have been sent to the nearest facility over 1,138 kilometers (707 miles) away in the city of Manaus. Considering travel is currently restricted in Brazil, it could be some time until the results are revealed. 

In the meantime, the people have been told to self-isolate. However, as they live in a maloca, a traditional communal house used by indigenous people of the Amazon, with 14 other people, it will be tough to contain the infection. 

The man, who first reported his symptoms at a hospital on Friday, March 20, had been working as a tour guide for a group of five American tourists, according to Amazônia Real. Although the tourist group did not display any symptoms, they are now being monitored by health professionals.

It's feared that some indigenous peoples will be particularly vulnerable to COVID-19 since isolated groups have little or no acquired immunity to other related diseases and common infections circulating in the general population.

“This could be catastrophic, Brazil's Javari Valley [is] home to many uncontacted tribes,” tweeted Survival International, an indigenous rights NGO. 

“Evangelical missionaries STILL planning to contact these tribes. Only massive outcry will stop them,” they added. 

Survival International also reports that evangelical Christian missionaries in Brazil have recently bought a helicopter to contact and convert previously unreachable tribes in the Javari Valley. Although their plans have been slightly hampered by the COVID-19 outbreak, US-based Christian group Ethnos360 has said they plan to use a newly purchased helicopter to convert isolated Amazon indigenous groups. They are also asking for donations to buy three more helicopters to contact indigenous people in Papua New Guinea (PNG), saying “Yes, people in remote PNG are still waiting to hear the Gospel!”

Indigenous leaders in Brazil's Javari Valley have denounced their plans as “a genocidal onslaught.”

"Our ancestors died of epidemics in the past – we don't want this to happen again! Our shamans our working to protect us but the authorities must prevent epidemics coming into our land," said Hutukara, an organization representing Yanomami indigenous peoples in Brazil.