The nation's top infectious disease researchers have repeatedly warned, if not begged, Americans to practice social distancing as the contagious coronavirus spreads through the population.

That's because, due to a woeful lack of testing in the nation, no one knows how many Americans are infected — and the resulting respiratory disease (COVID-19) is 10 times more lethal than the flu. Sunday morning, Marc Lipsitch, an infectious disease epidemiologist at Harvard University, emphasized this point, noting that the true number of infections is certainly "much higher" than confirmed cases.

But, though some folks are social distancing, many still clearly aren't. Some are even actively bragging about not doing it. This weekend, journalists and others reported that bars across the nation were packed in Boston, Chicago, Nashville, and New York City.

For those eager to ignore the recommendations of scientists who have squelched deadly virus epidemics in the past — like immunologist Mark Cameron who helped put SARS to rest — consider this: Between 20 to 60 percent of adults globally are expected to become infected, and some 15 percent of cases are severe or critical. It is people over 60 who are most vulnerable. So stopping the virus' spread will help your older relatives or parents from falling extremely ill, or worse.

"Social distancing is based on the principle of altruism," Jason Farley, a nurse practitioner for the Division of Infectious Diseases AIDS Service at the Johns Hopkins School of Medicine, told Mashable last week. "Treating everyone around you like it’s your 80-year-old grandmother is the circumstance we need to think about."

Many people — perhaps unaware they can walk around infected but without any symptoms for some five days or longer — clearly aren't considering the societal notion of altruism during a pandemic:

St. Patrick’s Day partiers hit the town over officials’ pleas amid coronavirus outbreak https://t.co/OaqgrgfaVb pic.twitter.com/mZUKITFj78 — Jake Wittich (@JakeWittich) March 14, 2020

Downtown Nashville is undefeated. pic.twitter.com/BFIOzukFct — Janna Abraham (@SportsPundette) March 15, 2020

I just went to a crowded Red Robin and I'm 30.



It was delicious, and I took my sweet time eating my meal. Because this is America. And I'll do what I want. — Katie Williams (@realkatiejow) March 14, 2020

How many old folks will have to die because the 26 year olds of Brooklyn love going to the single worst bar in America? https://t.co/yfpM9HXrUj — willy (@willystaley) March 14, 2020

Boston Police say they did NOT close down Southie bars early last night. Some bars did close well before 1am. This was what it looked like earlier in the day despite social distancing recommendations of 6 feet by city & state leaders. #COVIDー19 #WCVB pic.twitter.com/YxNdBZzbe1 — Josh Brogadir (@JoshBrogadirTV) March 15, 2020

I gave 4 rides tonight, all of them going to bars or clubs. After the 4th, I logged off, pulled into a parking lot, and sobbed. No one is quarantining. No one is listening. They don't know it yet, but they are killing each other. The sense of hopelessness is overwhelming. — Your Uber Driver (@uber_trips) March 15, 2020

Social distancing is not alarmist. In the words of Michael Leavitt, the former Secretary of the U.S. Department of Health and Human Services:

"Everything we do before a pandemic will seem alarmist. Everything we do after a pandemic will seem inadequate. This is the dilemma we face, but it should not stop us from doing what we can to prepare."

"Social distancing goes a long way to prevent the rapid spread of the virus," Akiko Iwasaki, a professor of immunobiology at the Yale School of Medicine, told Mashable.

"Social distancing is one of the most effective tools," agreed Suzanne Willard, a global health expert at Rutgers School of Nursing.

You are young and still wanna go out to bars cause you think, meh, I won't get this virus or if I do, it won't hit me hard. Read this: pic.twitter.com/n25Ch1E3kY — Michael Barbaro (@mikiebarb) March 14, 2020

It's true that social distancing is not the only critical tool. A prompt and radical uptick in testing — to isolate and treat infected people — is paramount. But social distancing will limit the spread of coronavirus, a disease so infectious it has traveled the globe.

"It takes an unprecedented public health response to put a lid on this one," said Cameron, who researches infectious diseases at Case Western Reserve University.

Coronavirus isn't just about you. It's about everyone you could infect.