(CNN) As Florida emerges from its coronavirus shutdown, the state is experiencing a surge of Covid-19 cases, with younger Floridians accounting for a significant number of positive tests.
The Florida Department of Health reported an additional 3,286 cases of coronavirus on Tuesday, bringing the state total to 103,503.
Medical experts and elected officials have attributed the rising numbers to a combination of more testing and more social contact as businesses reopen and, in recent weeks, to people's participation in large protests, although that has not been clearly established.
In Miami-Dade County, the state's most populous with 2.71 million people, data compiled by researchers at Florida International University shows that the number of positive Covid-19 tests has increased by an average of 35 every day during the past two weeks.
Researchers also found that hospitalizations, intensive care visits and ventilation use have all begun to increase over the past two weeks. Combined with a rise in cases, researchers say, this evidence points to increased community spread.
"Municipalities received guidelines on reopening but they do not have guidelines on when to pull back, which is why it is so critical to monitor the cases closely before the hospitals and ICUs start to have capacity issues -- which is something we have avoided so far in Miami-Dade County," said Dr. Mary Jo Trepka, the head of the epidemiology department at FIU.
Health experts can't really say for sure why cases have risen, but from the data, it's clear that community transmission is ongoing, Trepka told CNN. "More people are out and about," she said. "That has most likely contributed to it."
Trepka cited other factors as well, including children being out of school, the Memorial Day weekend and the recent protests in which some demonstrators did not wear masks. New research, however, suggests Black Lives Matter protests across the country have not led to a jump in coronavirus cases.
To limit transmission, she said, people should continue to perform the basic practices recommended by health officials over the past three months: Wear a mask, practice social distancing, wash your hands and, most importantly, stay home if you are sick or have symptoms.
"Stay home until you get the test result back and it's negative," she said.
Florida is one of the states that does not have a statewide requirement that masks be worn, though the state's health department recommends them.
Local governments such as Miami-Dade County require the use of masks. Miami Mayor Francis Suarez, a Republican, told CNN on Monday that large venues where rallies or sports events are held would not be opening and that Miami was not heading into the third phase of reopening because of the rise in cases.
"It has really nothing to do with an increased amount of testing. It has to do with more people that are getting tested coming out positive," Suarez said.
The county is seeing record numbers of Covid-19 patients, the Miami Herald reports. One medical center in Homestead reached its ICU limit on Tuesday after county officials identified it as a hot spot of new cases.
"Countywide, hospitals report far more beds available than beds filled with COVID patients. Still, hospital administrators and emergency room physicians say they're concerned by the surge, and that they've resumed near daily meetings with state regulators," the newspaper wrote.
Patients now are younger and not as sick as they were in April, The Herald wrote. That, combined with the knowledge gained then, means shorter hospitalizations and healthier results.
Over the weekend, Florida Gov. Ron DeSantis attributed the surge in cases to "testing more." He said the vast majority of the cases in Florida now are in people with no symptoms.
Counties such as Broward and Duval have a "large 20-to-30-year-old population, mostly asymptomatic. But we're also seeing that not only are they testing positive because they're testing more, they're also testing positive at a higher rate," said DeSantis, a Republican.
DeSantis said testing has also increased because of people "returning to the workforce."
States seeing an increase in the number of new Covid-19 cases will face "another ICU demand surge," said Dr. Jeanne Marrazzo, director of infectious diseases at the University of Alabama at Birmingham.
"There are time lags between the peak numbers we're seeing reported and the consequences that get people into the ICU. So you're looking at this two- to three-week period," Marrazzo told CNN on Tuesday.
"What makes me very concerned is that we are already seeing a spike in ICU admissions in a place like Florida," she said. "And yet, the cases are continuing to climb. So, we're going to be facing another ICU demand surge in not that long a time."
It is "really important for us to think about the implications there -- in terms of readiness and in terms of blunting the consequences of these increased cases," Marrazzo added.
Dr. Andrew Pastewski, the head intensive care unit physician at Jackson South Medical Center in Miami, is also seeing a surge in patients, he said.
"A week ago we had eight patients, none on a ventilator," Pastewski told CNN on Tuesday. "We were feeling like we were handling this well. We had a nice Covid floor, 24 beds with the capability of four ICU ventilators in that unit, so we thought we could use that as our Covid floor going forward.
"And within 10 days, we're now at over 40-plus patients, four on ventilators. We've had to find a second Covid unit and are looking for a third Covid unit right now."
Pastewski has two sets of patients in the ICU now: older patients who may live in a nursing home, and younger patients in their 50s and 60s, he said.
Some of his colleagues are not seeing an increase in Covid patients going into ICU units as of now, Pastewski said.
"Some of them don't know that there's any kind of Covid surge happening because they only handle the Covid ICU patients," he said. "My group at Jackson South sees every Covid patient in hopes of catching them before they get sick, so I know that the numbers are higher."
This recent rise in cases among young adults could lower Covid-19 death rates unless those same young adults infect others, according to a tweet from Dr. Tom Frieden, former director of the US Centers for Disease Control and Prevention.
"With younger age of recent infections in at least some places such as Florida, expect a lower death rate in this wave ... until the 20-to-40-year-olds who are infected today go on to infect others," Frieden, president and CEO of the initiative Resolve to Save Lives, tweeted Sunday.
The shift of the coronavirus pandemic to younger Americans is not necessarily good news, said Dr. Ashish Jha, director of the Harvard Global Health Institute.
Younger people are less likely to get sick and less like to die from the virus, Jha told CNN. But even if they aren't sick, they can infect others, he noted.
"Those younger people have parents. They have grandparents, and they are going to go see those people," he said.
"The more the virus spreads, the more everybody is vulnerable."