The United States has more coronavirus infections than anywhere else, with nearly 2.8 million of the globe's more than 11 million cases.
A recent surge in infections is large enough to cause several governors to roll back the easing of lockdowns that had begun in their states, just as many Americans are poised to attend July Fourth celebrations.
As the U.S. struggles to contain the virus, President Donald Trump addressed a largely unmasked crowd Friday at Mount Rushmore in South Dakota as he kicked off the country's observance of Independence Day. There were also no social distancing measures in place.
Public health officials have expressed concern that the South Dakota event will be the source of super-spreading the virus around the country.
Kimberly Guilfoyle, the girlfriend of one of the president's sons, Donald Trump Jr., has tested positive for the coronavirus.
In Britain, a study of the National Health Service indicated that cleaners, porters and office staff have been super-spreaders of the virus within hospitals. "If you think about it, these were the people moving around the hospital," Sir John Bell, the head of the government's antibody program, told The Telegraph newspaper.
Brazil said Friday it has approved clinical trials for a COVID-19 vaccine by China's Sinovac.
Brazil follows the U.S. with an infection count of 1.5 million.
On Friday, Brazil's President Jair Bolsonaro approved a law requiring people to wear face masks on streets and on public transportation. However, he vetoed clauses that would have required wearing a face mask in enclosed spaces, including churches, schools and shops. The president, who has been widely criticized by health experts for downplaying the severity of the virus, says such a move could violate property rights.
In another development, the World Health Organization updated an account of how it learned of the coronavirus outbreak. It said it was alerted by its own office in China, and not by Chinese government officials. The agency had earlier said that the first report of the virus had come from China without further specifying from whom the information came.
The United States has strongly criticized the World Health Organization for its early handling of the pandemic and its dealings with China and said it would withdraw from the group.