Medical officials in Rio de Janeiro and at least four other major cities have warned that their hospital systems are on the verge of collapse, or already too overwhelmed to take any more patients.
Health experts expect the number of infections in the country of 211 million people will be much higher than what has been reported because of insufficient, delayed testing.
Meanwhile, President Jair Bolsonaro has shown no sign of wavering from his insistence that COVID-19 is a relatively minor disease and that broad social-distancing measures are not needed to stop it. He has said only Brazilians at high risk should be isolated.
In Manaus, the biggest city in the Amazon, officials said a cemetery has been forced to dig mass graves because there have been so many deaths. Workers have been burying 100 corpses a day - triple the pre-virus average of burials.
Ytalo Rodrigues, a 20-year-old driver for a funerary service provider in Manaus, said he had retrieved one body after another for more than 36 hours, without a break. There were so many deaths, his employer had to add a second hearse, Rodrigues said.
So far, the health ministry has confirmed nearly 53,000 COVID-19 cases and more than 3,600 deaths. By official counts, the country had its worst day yet on Thursday, with about 3,700 new cases and more than 400 deaths, and Friday was nearly as grim.
Experts warned that paltry testing means the true number of infections is far greater. And because it can take a long time for tests to be processed, the current numbers actually reflect deaths that happened one or two weeks ago, said Domingos Alves, adjunct professor of social medicine at the University of Sao Paulo, who is involved in the project.
"We are looking at a photo of the past," Alves said in an interview last week. "The number of cases in Brazil is, therefore, probably even greater than what we are predicting." Scientists from the University of Sao Paulo, University of Brasilia and other institutions say the true number of people infected with the virus as of this week is probably as much as 587,000 to 1.1 million people.
The health ministry said in a report earlier this month that it has the capacity to test 6,700 people per day - a far cry from the roughly 40,000 it will need when the virus peaks.
"We should do many more tests than we're doing, but the laboratory here is working at full steam," said Keny Colares, an infectious disease specialist at the Hospital Sao Jose in northeastern Ceara state who has been advising state officials on the pandemic response.