An indigenous woman in a village deep in the Amazon rainforest has contracted the novel coronavirus, the first case reported among Brazil’s more than 300 tribes, the Health Ministry’s indigenous health service Sesai has said.

The 20-year-old from the Kokama tribe tested positive for the virus in the district of Santo Antonio do Iá, near the border with Colombia, 880km (550 miles) up the Amazon river from the state capital Manaus, Sesai said in a statement on Wednesday.

Four cases of coronavirus have been confirmed in the same district, including a doctor who tested positive last week, raising fears the epidemic could spread to remote and vulnerable indigenous communities with devastating effect.

Sesai said the woman was a medical worker who had been in contact with the doctor. She was the only person to test positive among 15 health workers and 12 patients tested after the doctor was found to have the virus, Sesai said. Their names were not made public.

The doctor had returned from vacation in southern Brazil to work with the Tikunas, one of the largest tribes in the Amazon with more than 30,000 people who live in the upper Amazon near the borders with Colombia and Peru.

The woman has not shown symptoms of Covid-19 and has been isolated with her family, Sesai said.

Health experts warn that the spreading virus could be lethal for Brazil’s 850,000 indigenous people, who have been decimated for centuries by diseases brought by Europeans, from smallpox and malaria to the flu.

They fear indigenous peoples’ way of life in communal hamlets under large thatched structures increases the risk of contagion if any single member contracts the virus.