Savannah on Monday reintroduced a mask mandate, following a trail blazed by Los Angeles County and St Louis in a bid to stop the soaring COVID-19 case numbers.
The mayor of the Georgia city, Van Johnson, said that the number of new cases was at a high not seen since March.
He said the latest seven-day rolling average of newly reported cases was 62.6 - up from 7.3 on June 28.
'Given our current situation, based on the advice of these esteemed medical professionals behind me, I have ordered the reinstatement of Savannah's mask mandate effective immediately,' he said.
Van Johnson, the mayor of Savannah, Georgia, on Monday announced that his city is bringing in a new mask mandate to stop the spread of COVID-19
The mayor tweeted a message informing Savannah's citizens about the new rules
A sign is posted inside Grand Central Market in Los Angeles on July 19. A new mask mandate went into effect on July 17
'How we handle this place where we are now will determine how our rest of our year returns.
'We've come too far and we've done so well. Our businesses are booming and things are looking up for us to go back here.
'But as far as I'm concerned, our first priority is to keep our citizens safe, to keep our employees safe. To keep our employees that are working in hospitality and tourism industry safe. And certainly keep our visitors safe.
'So it's for me, the short and long-term health effects associated COVID-19 are too high.'
He pleaded with people in his city to get vaccinated, as a matter of urgency, and pointed out that children cannot be currently vaccinated, and so are vulnerable.
'Anyone who has been hesitant about getting the vaccine,' he said.
'The wait and see what happens. Time is over.'
People wear face coverings as they pass through Union Station in Los Angeles on July 19
Johnson's announcement comes as Georgia is concerned about a rise in the Delta variant.
Case numbers have risen 203 per cent over the past two weeks, and the state currently has only 48 per cent of its population above 18 fully vaccinated.
Savannah's decision came on the day that the St. Louis area became one of the first in the United States to reinstate mask requirements..
Despite pushback from some elected officials, face coverings became mandatory Monday in indoor public places and on public transportation in St. Louis city and St. Louis County for everyone age five or older - even for those who are vaccinated.
As in Savannah, wearing masks outdoors is strongly encouraged, especially in group settings.
The decision comes as both of Missouri's urban areas see a big uptick in coronavirus hospitalizations that began in rural areas of the state, especially in southwestern Missouri.
Missouri ranks fourth nationally in the most new cases per capita in the past 14 days, according to data collected by Johns Hopkins University Center for Systems Science and Engineering to measure outbreak caseloads and deaths across the United States.
In Nevada, workers in Las Vegas and other parts of Clark County will have to resume wearing masks indoors. Customers will not be forced to, under new rules.
People shop in Hollywood, California, on July 19 - two days in to the new mask mandate
In Alabama - the state with the lowest vaccination level - the number of COVID-19 patients in hospital has climbed to more than 900 - a number the state has not seen since February.
The Alabama Hospital Association says there were 947 COVID-19 patients in state hospitals on Monday, up from 204 at the beginning of July.
The latest number is about a third of where the state was at the peak of the pandemic when there were 3,000 virus patients in state hospitals in January.
The head of the hospital association says the concern is not the number itself, but the steep upward trajectory in numbers.
Dr Don Williamson said the state has the solution in the form of the vaccine, but 'there is not a long line of people wanting to be vaccinated.'
Last week the governor of Alabama, Kay Ivey, a Republican, expressed her frustration at the low interest in vaccination among her state's residents.
'Folks are supposed to have common sense. But it's time to start blaming the unvaccinated folks, not the regular folks,' she said on Thursday.
'It's the unvaccinated folks that are letting us down.'
Ivey's state and others across the South are hammered by new infections - with three states in the region now accounting for 40 per cent of active cases nationwide.
'Almost 100 per cent of the new hospitalizations are with unvaccinated folks,' she said on Thursday.
'And the deaths are certainly occurring with the unvaccinated folks. These folks are choosing a horrible lifestyle of self-inflicted pain.'
She told reporters that she's done her best to fight the virus but 'can't make you take care of yourself.'
Kay Ivey's state of Alabama has only seen a third of residents get vaccinated - well below the national average. As a result, cases are surging and deaths will follow
Louisiana, another state with a low vaccination rate, on Monday saw hospitals cancel non-emergency surgery, to prepare for an expected surge in admissions.
Yet some struggling states are refusing to reinstate mask mandates.
The mayor of the county that hosts Orlando, Florida's theme park mecca, said on Monday that 'we are in crisis mode' when it comes to dealing with soaring numbers of COVID-19 infections.
Florida accounted for a fifth of the nation's new infections last week, more than any other state, according to the U.S. Centers for Disease Control and Prevention.
Orange County Mayor Jerry Deming said Monday that the home to Walt Disney World and Universal Orlando Resort is seeing about 1,000 new cases a day.
The state health department says more than 73,000 new coronavirus cases were reported in Florida over the previous week, nearly seven times the 12,000 reported a month ago.
Florida had 341 cases per 100,000 people over the past week - second only to Louisiana, according to CDC data.
Despite this latest surge, Governor Ron DeSantis said Florida will not return to government mandates.