NEW YORK (AP) — Anna Alexander, a property manager in Virginia Beach, Virginia, started the day Monday thinking that she might avoid shaking hands because of the coronavirus outbreak. Then somebody stuck out a hand to shake.

She took it.

"I'm a business person," Alexander, 65, explained. "But if somebody else does it next time, I might try to be careful because of the coronavirus."

As the viral infections spread across the globe, everybody has to make a decision: How worried should I be about getting infected, and what should I do about it?

Those decisions can have wide impacts. "Seriously peo...