-by Frank Cerabino

Florida Gov. Ron DeSantis has turned into a devoted bystander.

As Florida has become the national poster child for new COVID-19 infections, DeSantis has been perfecting his shoulder-shrugging technique.

Most recently, the governor has imagined a silver lining in the state’s grim coronavirus numbers: That it’s mostly young people who are getting infected with COVID-19, and they have little to fear from it.

“I think when you see the younger folks, I think a lot of it is more just social interactions, so that’s natural,” he said.

DeSantis contends there’s no reason to take more drastic action on a state level -- such as mandating masks, rolling back re-openings, and limiting gatherings -- because the virus outbreak in Florida now is just a young person phenomenon. And that’s good news.

“We’re open. We know who we need to protect,” DeSantis said. “Most of the folks in those younger demographics, although we want them to be mindful of what’s going on, are just simply much, much less at risk than the folks who are in those older age groups.”

Yes, 96 percent of people in their 20s who don’t have an underlying medical condition recover from the coronavirus without requiring hospitalization, according to data from the Centers for Disease Control and Prevention (CDC).

But when one of those hearty, young people get the virus, he or she passes it to co-workers, friends, family members and random people they encounter in the supermarket or in other public places.

And this is the gaping hole in DeSantis’ logic.

He must surely know this. And yet, he acts as if this “natural” spread of the virus by social interactions among members of a high-survivor group is not worthy of government action.

Here’s why that’s deadly wrong.

Scientists measure the contagious rate of an infectious disease by using a mathematical expression with the letter “R” followed by a subscript zero. It’s called the “R-naught.”

The R-naught expresses the average number of people who will become infected from a single infection. If the R-naught is a number less than “1,” it means fewer than one person, on average, will be infected by a previously infected person.

This would cause the infection to eventually sputter out.

If the R-naught is exactly “1,” it means that every infected person would spread it to one other person, which would keep the virus alive over time, but not to the level of an epidemic.

If the R-naught is greater than “1,” it means that each infected person spreads the disease to more than one person on average.

The higher the number, the higher the community spread. Measles, one of the most infectious diseases, has an R-naught of about 15.

The R-naught of COVID-19 was originally thought to be between 2.2 and 2.7. But recent data in a study published by the CDC this month, show strains of it with an R-naught of 5.7 -- meaning that one person spreads it on average to five or six other people.

“We further show that active surveillance, contact tracing, quarantine and early strong social distancing efforts are needed to stop transmission of the virus,” the study concluded.

So, it’s not responsible for a governor to build a public policy around voluntary compliance and the lack of centralized control because new infections are happening now disproportionately to a high-survivor group.

Not when we can reasonably assume that each of those young people will indiscriminately spread it to other Floridians in various risk groups.

And this will occur over and over again in cycles that happen in a matter of days.

As epidemiologist Adam Kucharski pointed out, the numbers grow quickly when you have an infectious disease with an R-naught of more than 1 and a rapid re-infection cycle.

Kucharski calculated that with an R-naught of 2.5. and a five-day gap between new infections -- meaning six cycles of infection each month -- one case of COVID-19 can blossom into 244 new cases (2.5 to the sixth power) in a month from that one case.

As the R-naught gets larger, the cases balloon exponentially. For example, with an R-naught of 5.7, a single coronavirus case blossoms after six cycles of re-infection to a total of 34,296 new infections.

And this explosive spread of a contagious disease isn’t contingent on whether the first spreader was a healthy, young person who didn’t require hospitalization.

So, it’s more than disappointing to hear our governor be such a complacent spectator.

“They’re young people,” DeSantis said recently in a news conference. “They’re going to do what they’re going to do.”