Authorities have been ordering persons into isolation when they were suspected of carrying infectious diseases since at least the 14th century.

Ships at that time approaching the Italian city of Venice from abroad were required to anchor offshore for 40 days; "quarantine" is derived from quaranta, the word for 40 in Italian.

The coronavirus pandemic has also led to a kind of reverse quarantine, in which institutions with vulnerable residents such as nursing homes bar outside visitors — including family members — from entering to minimize the risk of infection.

"Prior to this crisis, we had rarely seen these kinds of group orders imposed," says American University's Washington College of Law professor and leading quarantine expert Lindsay Wiley. "They don't raise the same level of constitutional concerns as mandatory orders applicable to everyone in an entire geographic area, including many who are unlikely to have yet been exposed."

Even while he's on board with the Bay Area's 21-day shelter-in-place order, which allows people to leave their homes only for "essential" activities, public health professor Mukherjea worries the public's compliance could wane as the days go by.

"I think if the government is not transparent about what is happening with our local [conavirus] numbers in terms of case counts," says Mukherjea, "you may see that the average person says, 'my day-to-day life is affected so dramatically, but nothing good is happening, why bother?' "

American University's Wiley says if compliance with orders confining people to their homes is not voluntary, there could be major problems.

"I'm certain that the health authorities behind this order are very much hoping not to enter a situation where there are mass arrests and people crowding the local jails," she says.

The key for Georgetown's Gostin, who wrote the Model State Emergency Health Powers Act for the Centers for Disease Control and Prevention, is for authorities to strongly recommend self-isolation for large populations but not have to enforce it.

"The first thing we want in this coronavirus response is to keep our head — not to be disproportionate, not to be draconian, but to gain the public's trust," says Gostin. "And once you lose the public's trust, once you cross a line that the public thinks is too far, we will be on the losing side of this battle."