MIAMI — With a new wave of omicron COVID cases surging in Miami-Dade County, the percent of local positive tests, known as the positivity rate, has soared, representing a fourfold increase since April and likely an undercount due to at-home testing.

On Monday, Miami-Dade County’s seven-day average COVID-19 positivity rate rose to 22%, up from a 5% rate on April 8, according to the county’s COVID-19 Daily Dashboard. The latest number is nearing the rates at the height of the omicron surge in January, when positivity rates scaled 35%.

“We should definitely be concerned now,” said Mary Jo Trepka, an infectious disease epidemiologist and professor at Florida International University. “In fact, we should have been concerned several weeks ago.”

Miami-Dade’s mayor acknowledged the rising case counts and positivity rates, but said county residents are in a better position to weather the surge, the sixth wave since the coronavirus began in March 2020, as a result of their vaccinations.

“Miami-Dade is now in a new phase of the pandemic,” the Office of Miami-Dade County Mayor Daniella Levine Cava told the Miami Herald on Thursday. “We have not beaten this virus, but we know how to control it. We are the most vaccinated county in Florida and our protective efforts are paying off.”

As of Thursday, 86% of Miami-Dade’s total population was fully vaccinated, about 2.3 million people. Florida’s fully vaccinated rate is 67.5%; the U.S. rate is 66.7%. Fully vaccinated means people have received either the single dose J&J/Janssen vaccine or two doses of the Pfizer-BioNTech or Moderna vaccines. It does not include a booster, according to the Centers for Disease Control and Prevention.

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Trepka says there is a positive note to the county’s high positivity rate: Hospitalizations haven’t reached the levels during omicron’s initial surge, which started in December, peaked in January and began waning in February. Immunity from the virus, whether from vaccination or previous infection, is keeping many out of the hospital.

“We have the staff, the beds and the resources to manage the current COVID-19 patient volume,” said Dr. Aileen Marty, professor of Infectious Diseases in the Department of Medicine at FIU Herbert Wertheim College of Medicine.

Two new omicron variants fueling surge

The rise in cases is being fueled by omicron subvariants BA.4 and BA.5, which are creating a surge in new COVID-19 cases across the country. On Tuesday, the CDC reported the two variants, first identified in South Africa in January and February, respectively, account for a combined 13 percent of U.S. cases for the week ended June 4.

In the first week of May, the two variants accounted for only about 1 percent of new COVID cases, the CDC said in its Tuesday update, which was the first time the CDC broke out the two variants in its weekly COVID-19 variant report.

Public health experts have said these variants may be able to evade some immune protections, making them more contagious.

On Tuesday, the first three cases of the BA.4 variant were found in Florida in Miami-Dade County, according to a lab report.

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Summer surge

In Florida, cases and positivity rates began to rise in the beginning of April. New cases slowly climbed, and by the end of the month, hospitalizations started to inch up — although not nearly to the levels of the January surge. Deaths have remained relatively low, with about 100 to 300 people dying from COVID-19 weekly in Florida since April.

By the first week of June, case counts topped the double digits. The state saw its seven-day average of new cases hit 10,927 Thursday, nearly double from a month ago when the seven-day average was 5,424, according to Miami Herald calculations of CDC data.

While Miami-Dade County is not making new safety recommendations, such as requiring masks in county buildings — mandates county leaders adopted during previous surges — the county says it has a plan to combat the surge.

Levine Cava released her BEST Plan, which urges the community to get vaccinated and boosted, get tested if you have symptoms or have been exposed and stay home if you feel sick.

The Centers for Disease Control and Prevention is recommending all South Florida residents, regardless of vaccination status, wear a mask indoors in public and on public transportation. That’s because South Florida’s four counties — Miami-Dade, Broward, Palm Beach and Monroe — have a high rate of community transmission, among the highest in the country.

Experts are echoing the same safety measures.

“We must ensure that our people are up to date on their COVID-19 boosters and influenza vaccines,” said Marty.

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Trepka stressed the importance of testing and staying home if you feel ill.

Unvaccinated filling up hospitals

Unlike COVID-19 surges of the past, hospitals haven’t become overwhelmed.

The dominant circulating strains of omicron are highly infectious and can cause severe disease, Marty said. However, high rates of vaccination in the community mean the infections don’t always lead to hospitalization, although the immunocompromised are at risk.

But for those who have not been vaccinated, it’s another story.

Says Marty: “76% of hospitalized patients have never been vaccinated for COVID-19, and virtually all vaccinated persons who end up in the hospital are elderly, immunocompromised, or have other serious debilitating conditions.”

Dr. Hany Atallah, chief medical officer of Jackson Memorial Hospital, said Thursday the majority of Jackson patients with COVID have not been vaccinated.

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“We’re seeing also typically what we’ve seen in the past, which is the protectiveness of vaccines,” Atallah said. “So the people who are in the hospital who are vaccinated tend to be less sick than those who are in the hospital who have never been vaccinated.”

On Thursday, Jackson Memorial had 124 patients hospitalized with COVID, with 26 of those patients in the ICU. On Jan. 12, during the peak of the omicron variant, Jackson had 564 patients who were hospitalized with COVID-19.

Across Florida, 3,105 hospitalized patients are suspected or confirmed to have COVID, with 297 in the ICU, according to Thursday’s report from the U.S. Department of Health & Human Services. During the delta wave last summer and the omicron wave in January, the number of patients in Florida hospitals surpassed 15,000 a day.

Atallah said current trends show hospitalizations decreasing by the end of June.

As healthcare workers toil through a sixth wave of the virus, he says it has been challenging to juggle professional and personal safety.

“This has become obviously a marathon,” he said. “And the marathon is not really over.”