Miami’s coronavirus testing data suggest we still don’t know how many are infected

Despite widely recognized community spread of the novel coronavirus in South Florida, tests continue to come back positive at a higher-than-average rate in Miami-Dade County, a reflection of testing that remains narrowly focused on those who are sickest, oldest or most likely to have been exposed, such as first responders or those who traveled to places with widespread transmission.

Over the past week, the percentage of positive test results in Miami-Dade has ranged from 12% to 14%, according to Florida Department of Health data. While that’s not anywhere near as high as New York’s rate — about 28% of people tested are coming up positive — it’s still considered an indicator that not enough testing is being done.

Experts say elevated positivity rates like the rate in South Florida signal that testing is still too limited to draw conclusions about how the virus is behaving in the area. Without clear, reliable data on who is infected, public health officials struggle to figure out how quickly the virus is spreading and where the hotspots are. Hospitals and healthcare providers, meanwhile, often can’t get patients tested until they are sick and then have to wait for days or longer for results.

In South Korea, where the virus was reined in partly through widespread testing, the positivity rate was as low as 3%. And it was about 7% at the University of Washington’s lab, which has cast a wide net to detect the spread of the novel coronavirus in that state.

In South Florida, even though Miami-Dade and Broward counties have the biggest numbers of known infections, testing criteria has remained much the same for weeks: largely restricted to those 65 or older who are showing symptoms, or those with relevant travel history or contact with a known confirmed case of COVID-19, the disease caused by novel coronavirus.

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Keith R. Jerome, head of virology for University of Washington Medicine, said positivity rates are raw data that should be carefully interpreted, as they depend heavily on the availability of testing in a given area.

“If not many tests are available, they are reserved for the sickest people who most closely fit the classic clinical picture for COVID-19, so the positive rate will be higher,” Jerome said. “If more tests are available, they may be used for frontline health workers with minimal symptoms, or other people who are less sick, so the rate is lower.”

At a White House briefing earlier this week, Dr. Deborah Birx, the federal task force on coronavirus response coordinator, contrasted New York City’s alarmingly high 28% positivity rate with the national average, which remains less than 8%.

Jerome said the stark difference between his lab’s positivity rate of about 7% and New York’s rate suggests that it’s not just how many people health officials are testing, but how big of a problem the virus is causing in a given area. Public health experts and government officials agree that New York’s rate is likely an indicator of high-level penetration of the virus, since the state is conducting far more tests than most and the rate is still abnormally high.

In Florida, that could be taken as reassuring on some level.

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“This may mean that [Florida] is relatively early in the course of your local outbreak,” Jerome said. “In practical terms, what that means is that there’s still time for social distancing to make a big difference in your community.”

Miami-Dade’s positivity rate has remained consistent even as thousands of tests have been added to the totals this week. Alex Greninger, a principal investigator at the UW lab, also said that Miami-Dade’s rate likely means that more tests have been given to people in hospitals rather than those who remain at home.

He added that, in light of testing supply shortages, those restrictions make sense, but there’s still a lack of clarity on what would be considered ideal.

“There’s a question right now: if there were unlimited testing capacity, what should the positivity rate be?” Greninger said.

There’s not yet a consensus on the answer to that question, Greninger said, adding that in a perfect world: “You want it at zero.”

Even inside the hospitals serving some of Miami’s sickest patients, frustration has mounted over the testing process. Carlos Migoya, CEO of Jackson Health System, said on Wednesday that the results of lab tests for the novel coronavirus are taking too long.

“If you wait until you get the positive results, you are now delayed by two to four days to get the information,” Migoya said. “That’s one of the greatest challenges we have.”

The lack of clarity leads to Jackson Health nurses and doctors using more personal protective equipment because they have to assume that anyone suspected is positive until their status is known, days later.

Dr. Richard Sutton, an infectious disease specialist at the Yale School of Medicine, said people who are without symptoms can still test positive and transmit the disease, which underscores the need for wider testing.

“If there are people out there who are positive and yet they are relatively asymptomatic and haven’t been tested, they can still interact with other people,” Sutton said. “There’s a chance they will still spread it.”

That’s also a problem for people who were able to get tested, but waited more than a week for results.

Jeff Feldman, a 64-year-old Miami attorney and former prosecutor, said he waited 11 days for his test results to come back. When they did, he was nearly fully recovered from COVID-19, but found out he had tested positive.

After initially being denied a test, Feldman said he was given flu medication and showed up at his office after he had finished it on the advice of his physician. Still feeling sick, he traveled to his second home in Naples, he said, before his fever returned and he managed to get a coronavirus test in Miami.

Feldman said that even though he and his wife were told they likely had the flu, they took precautions not to expose other people. Others, he said, might not think to do that.

“It’s what could have been, I guess, that’s significant here,” Feldman said, adding that he felt his physician did nothing wrong but was constrained by testing availability.

Feldman said the message being put out by federal officials and President Donald Trump, that issues with testing have been resolved, is a “joke.”

“When I watch the news conferences and compare what’s being said to my experience, it’s just ridiculous,” Feldman said. “It’s fictitious.”

Ben Conarck is a reporter covering healthcare at the Miami Herald, which he joined in August 2019. He was previously an investigative reporter covering criminal justice at The Florida Times-Union. In 2018, he and reporter Topher Sanders received Columbia University’s Paul Tobenkin award for outstanding reporting on race and the University of Colorado’s Al Nakkula award for outstanding police reporting for their multi-part investigation “Walking While Black.” Conarck has also extensively covered the Florida prison system.
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