Signs in the briefing room of the White House indicate social distancing measures being taken to separate reporters working at the White House, Monday, March 16, 2020, in Washington. Credit: Evan Vucci | AP

Social distancing has become a buzzword in recent days. The concept is simple, if fewer people are in close contact, it will slow the spread of illnesses like coronavirus.

It may sound too simple to tell people to stay away from one another to combat the virus, but the concept of social distancing is backed by math and science.

First, the math. Coronavirus is following a pattern of exponential spread.

“In any biological system, if you put a living organism into an environment where it can thrive, with unlimited resources and no predators or competitors, it will always grow in the same fashion: exponentially,” Ethan Siegel wrote Tuesday for Forbes.

Exponential growth means doubling. So, one case becomes two, two become four, four becomes 16 and so on. With little intervention, this quickly grows to millions of cases. The question is how quickly this growth occurs.

Worldwide, the number of coronavirus cases doubled in 24 days from the first known infection. In the U.S., the number of cases doubled in four days, according to the Forbes analysis. The number of cases in Maine went from 17 positive cases on Monday, to 32 confirmed and presumptive positive cases on Tuesday, following the exponential growth pattern. More than 100 Mainers are in isolation after possible exposure to coronavirus.

“ … [E]verything from wolves to parasitic wasps to yeast cells will grow exponentially, up until one of those assumptions fails to be true. Only at that point will growth become slower, and that holds the key to understanding how to mitigate the present pandemic,” Siegel wrote.

That’s where social distancing comes in. If the rate of transmission of coronavirus can be slowed, the exponential spread will also be slowed. This is the “ flattening of the curve” you’ve been hearing about.

The Washington Post offered an easy-to-understand visual representation of how this works.

“If people are less mobile and interact with each other less, the virus has fewer opportunities to spread,” Harry Stevens, a graphic reporter at the Post explained.

If three-quarters of the population stays home and limits interaction with others — moderate social distancing — the curve is much flatter, fewer people get sick and the rise in the number of cases is slower, giving the health care system more time to respond and to treat sick residents.

If only one-eighth of the population remains mobile, the curve is dramatically flattened.

In the Post simulation, moderate social distancing worked better than an attempted forced quarantine. This is instructive for a country like the U.S. where mandatory orders are often seen as authoritarian overreach.

Social distancing isn’t just a theory. The contrast of Philadelphia and St. Louis during the 1918 Spanish flu pandemic shows it can work. City officials in Philadelphia ignored warnings that the flu was spreading and went ahead with a huge parade to support the World War I effort. Hundreds of thousands of people attended. Within days, people began dying and about 16,000 people died in Philadelphia within six months. In St. Louis, where events were cancelled, schools closed and travel restricted, about 2,000 people died from the flu.

President Donald Trump and Maine Gov. Janet Mills are encouraging social distancing, because, although it will have serious negative economic consequences, it works. Schools and colleges are closed. Stores, including L.L. Bean, Apple and Patagonia, have closed. So, too, have gyms. Banks and credit unions are closing their lobbies. Businesses are encouraging employees to work at home where practical. Bangor has closed its city hall and state Bureau of Motor Vehicle offices are closed indefinitely. Bangor and Portland have imposed curfews on restaurants and bars to discourage people from congregating there.

Doug Fuss, who owns Bull Feeney’s, a Portland Old Port Irish pub, said closing on St. Patrick’s Day will be a big blow to his bottom line. But he said it was “100 percent the right thing to do.”

“If we stay in this together, then we can rise above it together,” Fuss said.

We are all in this together, but for now, we need to stay apart.