Florida has reported a record increase of more than 15,000 new cases of COVID-19 in 24 hours, a day after Walt Disney World in Orlando reopened and anti-mask activists held a rally nearby.
If Florida were a country, it would rank fourth in the world for the most new coronavirus cases in a day behind the US, Brazil and India.
Florida's daily increases in cases have already surpassed the highest daily tally reported by any European country during the height of the pandemic there.
Florida has also broken the state of New York's record of 12,847 new cases on April 10 when it was the epicentre of the US outbreak.
Walt Disney Co welcomed a limited number of guests to its two most popular parks in Orlando on Saturday with a host of safety measures including masks and temperature checks.
Coronavirus infections are rising in about 40 states, according to a Reuters analysis of cases for the past two weeks compared with the prior two weeks.
Nationally, the US has broken global records by registering about 60,000 new cases a day for the last four days in a row, according to a Reuters tally.
Hospitalisations and positive test rates are also rising in the states at the centre of the outbreak - Arizona, California, Florida and Texas.
Health officials have pleaded with the public to wear masks to limit the spread of the virus, but the issue has become politically divisive in the US, unlike many other countries that have seen far lower rates of infection and death.
Seven months into the pandemic, US President Donald Trump wore a mask for the first time in public when he visited a Washington DC-area military medical centre on Saturday.
Trump had previously refused to wear a mask in public or ask Americans to wear face coverings, saying it was a personal choice.
Many Americans still refuse to wear a mask, which health experts say helps stop transmission of the virus.
COVID-19 has killed more than 134,000 Americans.
Anti-mask activists organised a protest on Saturday at a grilled cheese restaurant and bar in Windermere, Florida, which is in Orange County, about 19km from Walt Disney World.
Anti-mask activist Tara Hill said the virus was very well-contained.
"Everyone is responsible for their own health care decisions ... We want our choices respected as well," she said.
Florida has posted record levels of coronavirus infections five times in the last 10 days.
In addition, more than four dozen hospitals in Florida reported their intensive care units are full due to a surge in COVID-19 patients.
Australian Associated Press
