The 20-year-old woman is believed to have contracted the disease from her colleague who recently returned from a holiday.
A woman from the Kokama ethnic group in the Amazon rainforest is the first Indigenous person in Brazil to test positive for the new coronavirus.
The COVID-19 pandemic has fueled fears about the possible impact for Indigenous peoples in the Amazon, who are particularly vulnerable to imported diseases.
The 20-year-old woman works for the public health system in the municipality of Santo Antonio do Ica, near the Colombian-Brazilian border. She works with a doctor who tested positive for the virus last week after returning from holiday, authorities said on Wednesday.
She has no symptoms so far. She and her family have all gone into isolation and are under observation, according to the Brazilian health ministry's Special Secretariat for Indigenous Health.
"Indigenous health is a major concern" during the coronavirus pandemic, health minister Luiz Henrique Mandetta said. "We have to be triply careful in these communities, especially the most isolated ones."
Indigenous tribes in the Americas have been historically isolated from many diseases against which much of the world has developed an immunity.
It is estimated that diseases brought by European colonisers wiped out more than 95 per cent of the Indigenous population of the Americas - and such groups remain vulnerable.
Mr Mandetta said even today, when Indigenous leaders return from trips overseas, they go into quarantine for two weeks to avoid bringing outside diseases back to their communities.
Twelve Indigenous patients and 14 other people who worked with the infected doctor are awaiting coronavirus test results.
People in Australia must stay at least 1.5 metres away from others and gatherings are limited to two people unless you are with your family or household.
If you believe you may have contracted the virus, call your doctor (don’t visit) or contact the national Coronavirus Health Information Hotline on 1800 020 080. If you are struggling to breathe or experiencing a medical emergency, call 000.
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