As many as 23 US states, mostly in the South and West, are registering a rise in new reported cases compared to the previous week, according to data from Johns Hopkins University.
Most of the states reporting surging numbers of cases have not previously seen a peak and fall — this is not a resurgence of cases, but a continued increase.
Florida became the seventh state to hit 100,000 confirmed cases of Covid-19 on Monday according to the state department of health. The daily number of cases reached a record 4,049 on Saturday, but that fell back on Sunday and Monday.
Governor Ron DeSantis has not made masks mandatory, but several cities have. Mr DeSantis said that local enforcement would be more effective than statewide penalties. Florida now has 100,217 confirmed cases, and more than 3,150 officially recorded deaths.
California, which reported some of the first cases in the US back in February, this weekend saw its highest number of hospitalisations — 3,574 on Saturday — and the most new cases in a single day — 4,515.
Governor Gavin Newsom announced that residents are now required to wear a face mask or covering in indoor public spaces, on public transportation, or in a healthcare environment.
As one of the first states to begin the process of reopening, Texas is now grappling with a surge in cases similar in size to both California and Florida, reaching a new daily peak of 4,430 new cases on Saturday.
Governor Greg Abbott has insisted that there is no cause for concern and dismissed a request from the mayor of nine of the largest cities in the state to allow them to make masks mandatory in their cities.
Mayor of Austin Steve Adler said on Sunday night that he wished the reopening of the state had been done slower with more attention to case numbers in each phase before moving to the next. Not mandating masks sends a message that this is all over, he said.
White House economic adviser Larry Kudlow said on Monday there is no second wave of the coronavirus pandemic, even though there are some flare-ups in states such as Florida, and it is unlikely there will be widespread shutdowns across the country.
“There are some hotspots. We're on it,” Mr Kudlow said in an interview with CNBC. “We know how to deal with this stuff now. It's come a long way since last winter and there is no second wave coming.”
Joining California, Florida and Texas, are Arizona, Colorado, Delaware, Georgia, Hawaii, Idaho, Kansas, Kentucky, Michigan, Missouri, Montana, Nevada, Ohio, Oklahoma, South Carolina, Tennessee, Utah, Washington, West Virginia and Wyoming.
Ten states have case numbers that are holding steady: Arkansas, Indiana, Iowa, Minnesota, Nebraska, New Mexico, North Dakota, Oregon, Virginia and Wisconsin.
States that continue to show decreases in the number of cases are Alabama, Alaska, Connecticut, Illinois, Louisiana, Maine, Maryland, Massachusetts, Mississippi, New Hampshire, New Jersey, New York, North Carolina, Pennsylvania, Rhode Island, South Dakota and Vermont.