South America has become "a new epicentre" of the deadly coronavirus pandemic, the World Health Organisation said Friday, following a surge in the number of Covid-19 infections.
"In a sense, South America has become a new epicentre for the disease. We have seen many South American countries with increasing numbers of cases," WHO emergencies director Mike Ryan told a virtual news conference.
"Clearly there is a concern across many of those countries, but clearly the most affected is Brazil at this point."
The novel coronavirus death toll in Brazil surpassed 20,000 on Thursday, after a record number of fatalities in a 24-hour period, the health ministry said.
The country's highest one-day toll of 1,188 pushed the overall death tally to 20,047.
Brazil has now recorded more than 310,000 cases, with experts saying a lack of testing means the real figures are probably much higher.
With its curve of infections and deaths rising sharply, the country of 210 million ranks third in the world in terms of total cases, behind the United States and Russia.
The death toll -- the sixth highest in the world -- has doubled in just 11 days, according to ministry data.
"The majority of the cases are from the Sao Paulo region," said Ryan.
"But in terms of attack rates, the highest attack rates are actually in Amazonas: about 490 persons infected per 100,000 population, which is quite high," he said of Brazil's vast northwestern state.
Brazil's health ministry has recommended using the anti-malaria drugs chloroquine and hydroxychloroquine to treat even mild cases of Covid-19 -- treatments President Jair Bolsonaro has pushed for despite the lack of conclusive evidence of their effectiveness.
US President Donald Trump on Monday made the surprise announcement that he is taking hydroxychloroquine, despite his own government experts saying it is not suitable for fighting coronavirus.
Ryan stressed that neither hydroxychloroquine nor chloroquine have been proven to be effective in the treatment of Covid-19 -- or in prophylaxis against the disease.
The two drugs are among a handful involved in WHO-coordinated clinical trials to find effective treatments for the disease. Some 3,000 patients are taking part in the trials in 320 hospitals across 17 countries.
"Our current clinical and systematic reviews carried out by the Pan American Health Organization, and the current clinical evidence, does not support the widespread use of hydroxychloroquine for the treatment of Covid-19 -- not until the trials are completed and we have clear results," said Ryan.