Hospitals are overcrowded, with people dying as they wait for treatment in some cities, and the health system is on the brink of collapse in many areas.
The country's total death toll is now almost 337,000, second only to the US.
But President Jair Bolsonaro continues to oppose any lockdown measures to curb the outbreak.
He argues that the damage to the economy would be worse than the effects of the virus itself, and has tried to revert some of the restrictions imposed by local authorities in the courts.
Covid vaccines: How fast is worldwide progress?
What is the Brazil variant and do vaccines work against it?
Political crisis and Covid surge rock Brazil
Speaking to supporters outside the presidential residence on Tuesday, he criticised quarantine measures claiming they were linked to obesity and depression and led to unemployment. He did not comment on the 4,195 deaths recorded in the past 24 hours.
To date, Brazil has recorded more than 13 million cases of coronavirus, according to the health ministry. Some 66,570 people died of Covid-19 in March, more than double the previous monthly record.
What is the situation in the country?
In most states, patients with Covid-19 are using more than 90% of intensive care unit beds though numbers have been stable since the past week, according to the health institute Fiocruz (in Portuguese).
Several states have reported short supplies of oxygen and sedative. But despite the critical situation, some cities and states are already easing measures limiting the movement of people.
"The fact is the anti-lockdown narrative of President Jair Bolsonaro has won," Miguel Lago, executive director of Brazil's Institute for Health Policy Studies, which advises public health officials, told the Associated Press.
"Mayors and governors are politically prohibited from beefing up social distancing policies because they know supporters of the president, including business leaders, will sabotage it," he said.
The far-right president, who repeatedly played down the virus, raised doubts about vaccines and defended unproven drugs as treatment, has seen his popularity plummet amid criticism of his handling of the crisis.
He has shifted his tone on immunisations recently, pledging to make 2021 the year of vaccinations. But the government has struggled with the rollout of its programme.
Critics say his government was slow in negotiating supplies amid a worldwide run, leaving Brazil facing delays in receiving jabs. Only around 8% of the population has received at least one dose, according to the Our World in Data tracker.
Epidemiologist Ethel Maciel said the country was in a "dreadful situation", telling AFP news agency: "At the rate we're vaccinating... the only way to slow the extremely fast spread of the virus is an effective lockdown for at least 20 days."
What is the Brazil variant?
Fiocruz says it has detected 92 variants of coronavirus in the country, including the P.1, or Brazil, variant, which has become a cause for concern because it is thought to be much more contagious than the original strain.
The variant is thought to have emerged in Amazonas state in November 2020, spreading quickly in the state capital Manaus, where it accounted for 73% of cases by January 2021, according to figures analysed by researchers in Brazil.
It has been linked to a spike in infections and deaths in a number of South American countries.
Coronavirus figures released by health authorities across South America on Monday show a number of countries grappling with a spike in infections and deaths.
Uruguay and Paraguay registered record numbers of daily deaths, while the total number of Covid cases surpassed the 13-million mark in Brazil.
The surge has been attributed to the spread of the Brazil variant.
The variant is thought to be more than twice as transmissible as the original.
What is the Brazil variant?
Brazilian public health institute Fiocruz says it has detected 92 variants of coronavirus in the country. Experts say that the development of new variants is not surprising: all viruses mutate as they make copies of themselves to spread.
On 25 March, Peru's health minister said that 40% of cases in the capital, Lima, were caused by the Brazil variant, and on Monday he said that cases had been detected "almost everywhere in Peru".
Cases of the variant have also been confirmed in Uruguay and Paraguay, both of which registered record numbers of daily deaths on Monday.
In Paraguay, health officials said that half of the cases on the border with Brazil were caused by the variant.
Bolivia has also registered cases of the variant and last week ordered the closure of its border with Brazil for at least a week, with a lockdown ordered for the border regions where the cases occurred.
Venezuela's President Nicolás Maduro has also blamed a recent spike in cases and deaths on the spread of the Brazil variant.
In Argentina, health officials have also confirmed the presence of the variant. However, doctors said on Monday that genome sequencing suggested that President Alberto Fernández, who tested positive for Covid on Saturday, did not contract one of the new variants.
And while vaccination is going ahead speedily in Chile and Uruguay, it has been slow in many other countries of the region.
The director of the Pan-American Health Organization, Carissa Etienne, has warned that the situation constitutes "an active public health emergency".
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