How long will social distancing for coronavirus have to last? It depends on these factors.

How long are we going to have to keep this up? The closed schools, work from home, six feet of personal space and zombie-apocalypse empty streets?

It's the question now preoccupying America as millions of parents silently scream it into the void. But it is an especially hard one for science to answer.

The best and most honest reply, according to epidemiologists and virologists, is simply: "It depends." It's not going to be over anytime soon - a matter of months rather than weeks. And these are the key factors that will determine just how many months:

- It depends on when U.S. cases finally reach their peak.

In recent days, the rapidly increasing number of confirmed U.S. cases has begun to resemble the beginning exponential curves of other countries such as Italy. While the virus continues to spread in Italy, the new daily cases of covid-19 in other countries like China and South Korea are finally tapering off - a sign that they have passed the peak of their immediate crises.

"It depends if a week from now, we look like Italy or South Korea," said Caitlin Rivers, an epidemiologist at Johns Hopkins Center for Health Security.

It took China roughly two months from beginning of its outbreak - and a month from the time the gravity of the situation was understood - for the country to reach its peak. And it took South Korea roughly half a month.

It is impossible, however, to say when that peak will arrive in the United States for many reasons - chief among them the fact that we don't yet know the true number of cases because of how limited testing remains in America.

The U.S. situation, one epidemiologist said, is the equivalent of someone asking an exterminator what it will take to get rid of rats in a basement they've been too afraid to enter for weeks. You have turn the lights on and examine the droppings first to figure out the scope of the problem. And the nation's response in the absence of that knowledge has been sluggish compared to other countries.

In the latest sign of how bad and how long this crisis could last, the Centers for Disease Control and Prevention said Sunday that all gatherings of more than 50 people should be halted for the next eight weeks.

- Even after the peak, we may need drastic actions to keep the virus at bay.

Two and half months after the virus emerged, China has partially lifted its draconian lockdowns in many areas. Schools have started reopening, and authorities have taken down the makeshift hospitals built in Wuhan at the height of the outbreak.

But new cases continue popping up. And the government has continued its use of temperature checkpoints and pervasive digital surveillance programs that track people's movements, and the streets even in its megacities are not as crowded as before.

[Coronavirus: How does it spread? What are the symptoms? When is it most contagious?]

The risk of new outbreaks still looms. That's why Chinese authorities introduced new restrictions on incoming travelers - just as some countries once banned Chinese travelers - to prevent the virus from coming back into China and starting new brush fires of transmission.

"We haven't seen how this plays out all the way yet in China," Rivers said.

We could see such second or third waves of outbreaks in countries still recovering from the first. Some experts think the virus will eventually infect 40 to 70 percent of the world's population.

So it's possible, even most likely, that after U.S. cases peak, Americans will still have to maintain some measures - such as isolating the infected, constant handwashing, even some degree of social distancing - until a viable vaccine is developed, which could take 12 to 18 months.

- It depends on unknown characteristics of the virus.

So much is still unknown about this virus and how it behaves.

Some have expressed hopes that the coronavirus, like the flu, will be affected by the change of seasons, with the flu waning with warmer temperatures in the spring and summer. If so, that could give Americans a respite from these drastic measures and much-needed time to prepare our health-care system rather than see them overwhelmed during a second onslaught of infections in the fall and winter. But no one knows whether seasons will have any affect.

Additionally, scientists still don't know for sure if surviving a covid-19 infection means you gain long-lasting immunity and, if so, for how long. There have been a few reports of possible reinfections, but many experts think those may be due to testing errors or a resurgence of the virus in patients who hadn't completely recovered.

- Much also depends on how much we’re willing to do, for how long.

How well America is able to flatten and bend its epidemiological curve of infections depends largely on how willing people will be to sacrifice individual conveniences and their desire to save the lives of others.

In Britain, for example, leaders last week said they were holding off on social distancing, large gathering bans and school closures, in part out of fear that citizens would quickly get tired of it.

"If you move too early, people get fatigued," Chris Whitty, chief medical officer for England, said Thursday. That decision, however, drew widespread opposition from experts - including more than 200 science and medical experts who published an open letter criticizing the plan. This is because a lot of epidemiological studies show the earlier you enact such interventions, the bigger their effect.

Even with the action being taken now in the United States, experts say hospitals will most likely run out of beds and ventilators and be forced to ration care, choosing which patients to save and which to let die.

"I don't know if people are ready now for how long they're probably going to have to keep up this social distancing. But as they see the hospital situation get more extreme, I think that attitude will change," said Natalie Dean, a biostatistician at the University of Florida, who is working on coronavirus vaccines with the World Health Organization and testing issues with Florida's health department.

As she spoke to a reporter Sunday night, Dean multitasked, taking her two kids on a walk around the block, with her eldest competing - loudly - at times for her attention.

"It’s stressful. It’s going to take adjustment for a lot of families. But to be honest, it’s too early given what’s still ahead to be asking ‘how long?’ " she said. “It’s like asking a fireman when you can move back in, but your house is still on fire.”