The number of deaths related to Covid-19 has passed 500,000 in Brazil, the second-highest in the world, as experts say the outbreak could worsen amid slow vaccination and the start of winter.
Covid-19 continues to spread in Brazil as President Jair Bolsonaro refuses to back measures like social distancing, reports the BBC.
The health institute Fiocruz says the situation is "critical". Only 15% of adults are fully vaccinated.
Congress is investigating the government's handling of the pandemic.
Dr Natalia Pasternak Taschner, a microbiologist at the Question of Science Institute, said that she saw little sign that the rise in victims would slow.
"People in Brazil are tired and they normalise death now so I think we still have a long way to go," she said.
"If we're not successful in changing the behaviour of people and if we don't have campaigns for mask wearing, social distancing and vaccinations coming directly from the central government we're not going to be able to control it."
President Bolsonaro has been heavily criticised for not implementing a co-ordinated national response and for his scepticism toward vaccines, lockdowns and mask-wearing requirements, which he has sought to loosen.
In rallies in Rio de Janeiro, Brasilia and elsewhere, furious Brazilians carried banners with slogans like "Bolsonaro must go" or simply "500,000."
"His position on Covid and his denialism are absurd. He has abandoned reality and common sense. There is no explaining this, it is surreal," Robert Almeida, a 50-year-old marching in Rio, told AFP.