Americans were also told that those exposed to the virus would be quarantined for weeks, including some well-known figures.

So consumers had good reason to be worried, but they were given no guidance about how to prepare for a possible quarantine, what to buy or how much, Ariely said.

That’s why panic feeds on itself, he said. “When we don’t get a rule for behavior, we look at the people around us.”

March 13, 2020 Atlanta: Panic buying occurred at the Kroger Marketplace at Glenwood Avenue in Atlanta on Friday, March 13, 2020. The Coronavirus pandemic is affecting everyone across the State of Georgia and Metro Atlanta. JOHN SPINK/JSPINK@AJC.COM Credit: JOHN SPINK / AJC Credit: JOHN SPINK / AJC

The worry about quarantines and "social distancing" gave people some rational reasons to panic, said Catherine Eckel, director of the Behavioral Economics Program at Texas A&M.

Yet there is a line between action and over-reaction, she said.

"It's uncertain and people are stressed and scared and if you have to spend two weeks at home, you've gotta have stuff," Eckel said. "But to buy a year's supply of toilet paper? That's nuts."

But even overreaction serves to make people feel better, said Nadine Kaslow, professor of psychiatry and behavioral services at Emory's medical school, as well as chief psychologist of the Grady Health System.

People need to assert control, even when it’s an illusion, she said. “People feel so uncertain and so scared. So buying things is a way to say, ‘I’m going to take care of myself.’”

Americans have been told how to minimize their personal exposure to the virus, but individual actions can put other people at a disadvantage, she said. "If you have a lot of toilet paper, it's not going to keep you from getting COVID-19. And it might prevent other people – like someone who is poor or elderly – from getting it."

What is especially unnerving during a crisis is the feeling of being on your own, Kaslow said. “We all feel like ‘I’m going to take care of myself.’ But we don’t have a sense that we are going to take care of the community.”