Which sparks set off Miami's COVID wildfire? The clues are in the cases, experts say

Jul. 17--When COVID-19 roared back to life across Florida in mid-June after several weeks of relative quiet, Miami-Dade County quickly became a hot spot far exceeding other parts of the state, despite a more cautious reopening and a relatively early shutdown order.

Public health experts say there likely is no single reason why Miami-Dade has seen the highest number of cases, hospitalizations and deaths due to COVID-19 in Florida. They say robust contact tracing can provide clues, but without details from Florida's health department to identify where outbreaks are occurring and among whom, they can only offer theories -- from so-called "super spreading events," to the socioeconomic conditions of the region and migration patterns.

""This is the reason we do case investigations," said Jennifer Nuzzo, a public health epidemiologist with the Johns Hopkins Center for Health Security. "We don't just collect numbers of cases, we ... find out who they are and why did they get sick, and how did they get sick."

Knowing whether a new wave of infections is stemming from bars or the essential workforce or some other source, Nuzzo said, could help local officials halt a new outbreak before it triggers another lockdown.

Those types of investigations would also reveal super spreading events, where one person can infect dozens or even hundreds of others. Bill Hanage, an epidemiologist at Harvard T.H. Chan School of Public Health, said he believes a lot of the variation in which cities have been hit the hardest during the summer resurgence depends somewhat on misfortune.

"If you get unlucky and you get a couple of those happening within a relatively small area, then it introduces hundreds of cases to a community ... instead of a slow, deterministic build," Hanage said.

Miami-Dade's shutdown order on March 26 was key to preventing a larger outbreak, Hanage said. Gov. Ron DeSantis ordered the state to shut down on April 1. But as the rest of the state reopened in early May, followed by Miami-Dade, Broward and Palm Beach counties nearly two weeks later, South Florida remained the hardest hit area despite closing earlier and reopening later.

Another possible explanation is that Miami-Dade has a high number of frail seniors on Medicaid, the public health insurance program for low-income Floridians. Many of them may receive care at home and often live with family members rather than in a nursing home, where Florida has focused much of its preventive efforts, said the state's former Medicaid director, Justin Senior.

Senior, who is now president of the Safety Net Hospital Alliance of Florida, a lobbying group, said Florida's resurgence of COVID-19 has been marked by increasing infections and hospitalizations among younger people, who can be a thunderhead, or warning sign, of a coming storm of infections in the elderly.

"You won't get nursing facility deaths," he said, "but you have young people going out, interacting with the community and coming back in. ... It's something to think about."

Senior surmised that migration patterns likely play a role, too, given that Miami is a gateway for domestic and international travelers.

"If you look at hot spots around the world. They have been New York and New Jersey in the U.S. It's been Western Europe, and now it's South America," he said. "And what is Miami to all of those places but kind of a crossroads where they all meet."

Though Senior is not a trained epidemiologist, Hanage, the Harvard professor, agreed that travel patterns -- both domestically and internationally -- are "certainly worth taking seriously."

"You can see that, for instance, one of the major reasons New York City was such an epicenter early on is because there were lots of flights ... including from Europe," Hanage said.

Though public health experts agree on the importance of contact tracing, Miami-Dade Mayor Carlos Gimenez has recently said that the benefits of contact tracing were limited given the uncontrolled spread of the virus in the county.

Nuzzo, of Johns Hopkins, said that local officials shouldn't give up on contact tracing even if they can only get to a small number of the cases. Those cases could still inform where the risk points in the community are, she said.

"I can understand the desire not to shut down restaurants and things that are driving the economy," Nuzzo said. "But if you can find places that are riskier than others and intervene there, that might help you avoid a shutdown."

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