One month after the peak of Florida’s spring break, the number of residents infected with more infectious mutated strains of COVID-19 has exploded, rising sixfold since mid-March and leaving 122 people hospitalized.

The information, disclosed in response to a lawsuit by the Orlando Sentinel against the Florida Department of Health, shows the total as of Thursday reached 5,177 cases involving five “variants of concern” — a designation from the U.S. Centers for Disease Control and Prevention for mutations that make the virus more transmissible, deadly or resistant to treatment and current vaccines.

In 31 of those cases, the people infected died.

“This is kind of what a lot of public health folks have been afraid of, and why we’re trying to emphasize the need for continued caution as we move forward,” said Zinzi Bailey, a social epidemiologist at the University of Miami Miller School of Medicine. “My biggest fear is that, if we become more lax with our masking and our social distancing, we will actually start creating our own variant” — including, potentially, one that could evade current vaccines.

The data comes as the White House announced an almost $2 billion plan on Friday to enhance the nation’s ability to track coronavirus variants — a move a top COVID advisor Andy Slavitt said is needed to “detect these variants early on before dangerous outbreaks.” About half of the money would go to federal and state efforts to test for the variants.

In Florida, it’s impossible to know how many cases in the recent surge can be traced to spring break activities, when crowds flocked to beaches and tourism hotspots, often without masks.

“Whether we can link any of these rises to spring break, up to a point, we’re doing a little bit of speculation,” Bailey said. “But from a basic logic standpoint, we would anticipate that people coming from all across the country who might be exposed to different kinds of folks, whether that’s in their hometown or in the airport, it’s always going to be a possibility.”

State health data also shows younger people in Orange County now make up higher percentages of infections from the highly contagious variants, and on Thursday the top public health official in Orange County warned that more younger residents are now being hospitalized than older ones — in part because over 75% of Orange County’s senior population has been vaccinated against COVID-19.

While the bulk of the variant cases have remained in South Florida — Broward reported over 1,200 cases and Dade had 774 — Central Florida counties now report hundreds of infections locally. Orange County has had 209, Seminole 98, Osceola 94 and Lake 57.

None of the Central Florida patients died, but several were hospitalized.

And because less than one-half of 1% of cases are studied for the mutations, the variants are assumed to be circulating at a much greater volume.

The most common strain of the virus continues to be B.1.1.7, a variant first detected in the United Kingdom, which is thought to be as much as 50% more infectious and potentially causing more hospitalizations and deaths. Current vaccines are effective against the variant.

But other strains are now spreading rapidly for the first time, including B.1.427 and B.1.429 — both traced to outbreaks in California. Both are about 20% more infectious than the original COVID-19 strain, and both are considered “moderately” more difficult to treat and prevent. At least one case of those variants has been found in each Central Florida county.

Additional strains in Florida include the P.1, first detected in Brazil and Japan, and B.1.351, traced to South Africa.

All but 129 of those infected reported no travel history, but nearly half had contact with someone else infected by a variant. For the remainder, the source of infection is unknown.

A handful of the infections were initially reported as long ago as July 2020 but not classified as variants until recently, after the virus in their bodies was studied more closely. But a large number were first sickened in March.

In mid-March, the Sentinel filed a lawsuit against the Florida Department of Health to get the variant data on a county-by-county level after numerous requests for the information over the preceding two months. The suit claimed the data is vital to the “strong, immediate need ... to understand how the virus continues to spread and affect Floridians.” A settlement in the case in pending.

Last December, the Orlando Sentinel filed a lawsuit against Gov. Ron DeSantis and his office for failing to provide the weekly White House Coronavirus Task Force reports in a timely manner. In early January, the state agreed to settle that lawsuit, providing all past reports and agreeing to release future reports within two business days. It also agreed to pay $7,500 in attorney fees.

ksantich@orlandosentinel.com