Sao Paulo (CNN) Fears are growing that the coronavirus could ravage Brazil's indigenous communities, following the death of a teenage boy in the Amazon region.

A member of the Yanomami people, the 15-year-old boy from the village of Rehebe in northern Brazil had been studying in a nearby town, before returning to his ancestral village where he began to feel symptoms and was transferred to a hospital. He died on Friday from complications related to COVID-19, according to the Health Ministry.

"We have to be extremely careful with indigenous communities," Health Minister Luiz Henrique Mandetta said after the Yanomami boy first tested positive. "The government is concerned about indigenous health. We are providing helicopters to withdraw people and take them to more sophisticated health centers."

Some 800,000 indigenous people live in villages throughout Brazil. They may be particularly endangered by the pandemic, with some tribes never having had previous contact with the outside world, and others living far from healthcare facilities and without basic sanitation facilities.

The teenager was one of nine indigenous Brazilians to test positive for coronavirus. Three have died, according to the ministry's Special Secretariat of Indigenous Health, which only monitors indigenous people living in traditional villages or communities.

The Yanomami live in the rainforests of northern Brazil and southern Venezuela. Because they are largely isolated from the outside world, they are more vulnerable to even common viruses. There are an estimated 38,000 Yanomami today, according to the indigenous rights group Survival International.

The nonprofit Socio-Environmental Institute (ISA) has warned the virus could spread among the Yanomami through miners who had illegally entered indigenous territory.

"Today, without a doubt, the main vector for the spread of COVID-19 inside the Yanomami Indigenous Territory is the more than 20,000 illegal miners that go in and out of the territory without any control," ISA said in a statement on its website.

Indigenous rights activists warned that illegal mining and logging on indigenous lands, which have increased since Brazil's pro-development President Jair Bolsonaro was sworn in last year, now pose an even greater threat to remote communities in general and the Yanomami in particular.

The nearest hospital in the capital of Roraima state has only 20 hospital beds equipped to deal with COVID-19 patients, according to authorities.

In the neighboring state of Amazonas, more than 90 percent of ICU beds are already occupied and the incidence of coronavirus in relation to the population is the highest in Brazil at 19.1 per 100,000 inhabitants, according to the Health Ministry. The number of confirmed cases in Brazil rose to 23,430 on Monday and deaths related to COVID-19 reached 1,328.

The mayor of Manaus, the riverside capital of Amazonas and the biggest city in the region, told CNN that the health system was already collapsing. "There aren't enough ICUs to meet demand," he said. "I would say that the private options are headed towards exhaustion and the public part has collapsed."

Over the weekend, Mandetta, the health minister, said authorities were building a field hospital in Manaus to attend to the many indigenous communities.

"The emerging spread of COVID-19 could have a devastating effect on indigenous peoples, particularly those living in voluntary isolation, due to their vulnerable immune systems, lack of access to healthcare facilities, and lack of potable water and sanitation infrastructure in villages," the watchdog group Amazon Watch warned even before the first case of coronavirus in Brazil's indigenous population was confirmed earlier this month.

The first indigenous person to test positive for COVID-19 was a 20-year-old woman of the Kokama people in Amazonas state. Many villages have responded to the crisis by barring access to outsiders and encouraging villagers to avoid communal gatherings.

"Besides uncontacted tribes, the pandemic is particularly worrying for many other indigenous people given their communal ways of life which could encourage its spread within communities, and, in some cases, their geographical distance from hospitals," said Sarah Shenker, a campaigner for Survival International.