The U.S. logged nearly 4.7 million known cases of Covid-19 on Sunday as public health officials renewed pleas for Americans to wear masks and avoid large groups.
By Sunday afternoon, there were nearly 18 million known cases of the quickly spreading disease caused by the novel coronavirus, according to the Johns Hopkins University disease-tracking map.
Nearly 155,000 Americans have died from the virus so far.
At the same time, cases in Brazil have also exploded to 2.7 million and India to nearly 1.8 million, according to Johns Hopkins.
While other nations such as Japan -- which has nearly 40,000 total known cases -- have raised alarms about an uptick in infections, no other country besides the U.S., Brazil and India have officially reached a million cases, though Russia's official numbers are edging near that mark.
Several former global hot spots such as Spain have kept their outbreaks fairly stable when compared with the surge seen in the U.S. over the summer, despite a recent resurgence in some European countries that's been largely blamed on younger people.
If the vast majority of Americans -- around 90% of them -- wear a mask when in public and avoid crowds, it would be as effective as a "complete shutdown," said Health and Human Services Secretary, Admiral Brett Giroir, on NBC News' "Meet the Press on Sunday."
"You've got to institute these measures," said Adm. Griroir, a medical doctor, "because the virus will keep doing what the virus does, unless we make an affirmative change."
Still, even in some Northeastern states -- such as Massachusetts -- known for lowering case counts from spring, many people could be seen over the weekend gathering closely in groups and at outdoor restaurants and parks with and without masks.
That state and some others in the region have seen slight increases in cases in recent weeks.
Also, nations shouldn't rely solely on masks to stamp out the virus, an epidemiology expert at the University of Hong Kong's medical school told TheStreet last weekend.
"Mask wearing would certainly help, but we have seen in Hong Kong that universal use of masks is not sufficient to stop Covid-19 transmission in the community," Ben Cowling, a professor at the Hong Kong University School of Public Health, told TheStreet. "Masks work, but we can't rely on masks, we need additional public health measures, as well as masks."