Gov. Charlie Baker plans to announce later this week whether the coronavirus order closing nonessential businesses in Massachusetts will be extended.

According to a new Massachusetts General Hospital simulator, the decision should be clear.

As other states across the country began easing restrictions meant to curb the spread of COVID-19 over the weekend, researchers at the Boston hospital released the new interactive online tool predicting a second wave of COVID-19 infections and deaths this summer if shutdown orders are lifted this spring — both across the country and in Massachusetts.

According to the MGH simulator, the state’s business closure order and stay-at-home advisory should remain in place for another 12 weeks — or until roughly July 20 — to ensure against a late-summer surge in COVID-19 hospitalizations and to keep the number of statewide deaths due the disease just under 5,000 through the end of August. As of Monday, the COVID-19 death toll in Massachusetts stood at just over 3,000.


But if the state’s current restrictions were allowed to expire in four weeks and replaced by “minimal restrictions,” on May 25, the simulator predicts catastrophe.

The outbreak would accelerate again in July, killing more than 27,000 people in Massachusetts and infecting more than 2.8 million people — or roughly 40 percent of the state’s population — by the end of August. And if restrictions were lifted in just two weeks, the model predicts 42,700 deaths — and nearly 3.4 million cumulative COVID-19 cases in Massachusetts alone. In both scenarios, the state’s health care system would be completely overwhelmed by a second surge of patients dwarfing the number available hospital beds, according to the model.

Jagpreet Chhatwal, the MGH project lead, says the simulator is intended to inform coronavirus response efforts in the midst of the quickly changing and uncertain environment. But the staggering worst-case numbers belie the fact that the somewhat rigid, if illustrative, tool doesn’t cleanly map onto the policy options before the Baker administration.

The simulator models three differing intervention levels: a complete travel lockdown, the state’s current orders, and “minimal restrictions” — the latter of which includes no state mandates and only “learned social awareness” about the disease.

In reality, such an abrupt snapback to normal is out of the question; officials in Massachusetts and neighboring states are planning for a gradual easing of restrictions in which businesses can reopen only under stringent social distancing rules. The Baker administration is also funneling resources into containment strategies like testing and contact tracing.


Even with those efforts in mind, Chhatwal told WBUR in an interview Sunday that the model suggests the state shouldn’t lift restrictions until the end of June, when the state will have enough testing to isolate all active COVID-19 cases.

“Before that, if we lift restrictions, the virus can spread in the community, which can be difficult to trace,” said the MGH researcher and assistant professor at Harvard Medical School.

Chhatwal added the state “definitely” shouldn’t lift restrictions on their current expiration date, May 4.

“We could see a spike happening within the next two to three weeks after the restrictions are lifted,” he told WBUR.

Boston Mayor Marty Walsh told reporters Monday that there was “no question May 4 is too early” to reopen nonessential businesses. Baker has also stressed that restrictions won’t be lifted until Massachusetts sees a sustained decrease in new coronavirus cases; the governor said Monday that while hospitalizations due to COVID-19 have plateaued, the state is still in the midst of its surge.

MGH’s simulator also modeled the disease’s trajectory for the entire country and for each of the other 49 states, plus Puerto Rico. It portends more dire outcomes in states like Georgia that are more aggressively loosening their orders; even lifting restrictions gradually over the next month could result in over 23,000 deaths in the Peach State, according to MGH officials.

The implicit warning is similar at the national level.

While the orders have been implemented at the state level, President Donald Trump has pressed to reopen the economy as the number of coronavirus cases across the country appears to stabilize. More recently, even the White House’s own coronavirus response leaders have said certain social distancing rules will continue through the summer.


MGH’s simulator predicts 1.1 million deaths — and an overwhelming peak of 7.9 million hospitalizations in August — due to COVID-19 if the current restrictions were lifted across the board by May 25. But if current interventions remain in place until June 22, the model predicts 86,000 deaths due to the disease — and declining hospitalizations since the peak of 63,800 on April 21.

“Our analysis shows that even a week’s time can have a huge impact on the future trajectory of COVID-19,” Chhatwal said.

Mass. remains closed through May 18

Get Boston.com's e-mail alerts:

Sign up and receive coronavirus news and breaking updates, from our newsroom to your inbox.