This is a do-or-die week in San Diego for fighting the coronavirus here, and it’s crucial for everyone to stay home, says a local scientist whose stark warning about the potential for catastrophe spread across social media on Tuesday.

“There are going to be a lot of people carrying and shedding the virus sometime this week … Taking everything together, this is a terrible week to be around other people,” wrote Forest Rohwer, a scientist who studies viruses at San Diego State University, in an email to colleagues that spread beyond the college community to websites like Facebook and Reddit.

Rohwer, who studies viruses in people and in the ocean, didn’t intend for the email to reach the public. “It was just for academics in my lab, honestly, to tell them what it looks like and where we’re at,” he said. But he’s happy to elaborate on why he thinks the next few days are so important in the battle against the coronavirus in San Diego.

In an interview, he said this is an “inflection point” — “a crucial week to flatten the curve” — because models suggest that California in general and San Diego specifically are about two weeks away from exploding past the capacity of hospitals to treat coronavirus patients.

“If we don’t want to let this balloon out of control, we need to stop it literally right now,” he said. The growth in cases “becomes impossible to stop when it really starts going. That’s how those exponentials work.”

He’s talking about how coronavirus cases have been growing exponentially in some parts of the world – doubling, then doubling again at an even faster rate until thousands are sick and dying. In the United States, according to CNN, deaths from the virus doubled from 100 to 200 over three days last week, then doubled again to 400 over two days by Sunday. Another doubling – to 800 – appears likely on Wednesday.

This week is important, he said, because models suggest that cases could overwhelm hospitals two weeks from now under some scenarios. It typically takes about two weeks for patients to need to be hospitalized after they’re infected, so this week is what he calls the “inflection point” that will decide whether we go down a road toward extreme sickness and death.

“The easiest way to think about it is to call it the point of no return, or a break point: A point in time where if too many people get infected, we won’t have enough hospital beds, and that means we’ll start having much higher death rates,” he said.

Rohwer pointed to the Covid Act Now model, created by a team of researchers, that estimates that California’s hospitals will become overwhelmed by April 7 — two weeks from now – if the state’s residents do nothing to prevent the spread of the virus. Nearly 800,000 Californians will die under this scenario.

Simply engaging in “social distancing” would push that date forward to April 19 and lead to an estimated 597,000 deaths. But the model estimates that hospitals won’t reach capacity before mid-summer if the state adopts a “shelter in place” strategy – which it has done – for three months. In this scenario, however, deaths in the state would reach 18,000.

San Diego County health officials are working on a model to predict local cases. But Dr. Wilma Wooten, the county’s top public health official, declined on Tuesday to tell reporters anything about what these efforts have produced.

As of Tuesday, San Diego County reported 242 cases of patients who tested positive for coronavirus and 45 total hospitalizations (possibly including patients who were released). Only 16 of the hospitalized patients were over the age of 60, and five were under 30. One resident has died in the county, and another resident died in another county.

What should we do this week? Stay away from other people, Rohrer said, and understand that we’re in a danger zone where what we do – or don’t do – matters not just to us but everyone else.

“We really are at that critical point,” he said.