Like a homeowner suddenly finding his walls are infested with termites, the U.S. discovered over this weekend what many other nations in Europe and Asia had already: The coronavirus has been spreading undetected for weeks. 

As of Sunday afternoon, the nation found more than 500 total cases and more than 20 had died in several states, including in Florida. New York state reported 105 cases alone as of Sunday afternoon, and declared a state of emergency.

“I think we're getting a better sense (of the disease) as the days go by,” Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, told NBC News’ Chuck Todd on “Meet the Press” on Sunday morning. “Unfortunately that better sense is not encouraging, because we're seeing community spread.”

Fauci warned the vulnerable to avoid large crowds, long trips -- "and above all don't get on a cruise ship."

Over the next few months, said Fauci, the goal would be to prevent the spread of the virus from within the country and from outside of it, and he talked up "social distancing."

"It's common sense stuff," he said, "you don't want to go to a massive gathering.... Particularly, when you have community spread, you may not know at any given time that there people who are infected."

While Fauci spoke generally about the dangers of large public events and crowds, he didn't push some of the quarantine measures taken in places like Italy or the school closings in several places such as Japan. But he did note that some of the "draconian" clampdowns in China did help slow the spread there, despite their negative side effects.

"I think they did prevent a broader spread," he said.

But the idea of "social distancing" -- even closing schools and cancelling of events -- could help here as well, several experts recently told TheStreet.

"Viral spread in schools is a concern," said Dr. C. Jason Wang, associate professor of pediatrics and director of the Center for Policy, Outcomes and Prevention at Stanford University School of Medicine, by email. Wang added that "tele-education" should be considered in the case of school closures.

"We need to expand testing in kids. This disease is clearly mild in them, which is great (they won't die) but they may be epidemiologically important," said Dr. David N. Fisman, a professor of epidemiology at the University of Toronto, in an email last week to TheStreet.

Dr. Fisman noted that "active social distancing" such as cancelling major league sports games and concerts and closing schools and churches before an actual crisis "may be the way to go," but he added, "it's hard to mobilize public support for that."

Another expert, Steven Riley, professor of infectious disease dynamics at Imperial College London, also noted that the World Health Organization had detailed the effectiveness of social distancing regulations in China. But, in a brief email last week to TheStreet, he noted that "it's not yet clear how the they will be maintained nor how feasible such stringent measures are in other settings."

An example of community spread in the U.S. most recently was found when a group of people who had attended a Biogen  (BIIB) - Get Report event in Boston turned out to be infected afterward. Earlier cases of community spread were spotted in Washington state and New York.