MGH coronavirus simulator suggests Mass. fatalities would spike if restrictions lift suddenly

Massachusetts General HospitalErin Clark/Globe Staff

As some states across the country begin loosening restrictions meant to slow the spread of the novel coronavirus, a new interactive online tool from Massachusetts General Hospital allows public health experts and armchair epidemiologists to chart the possible outcomes of different reopening strategies.

The COVID-19 Simulator, which allows users to model different scenarios through the end of summer for the entire nation or one state at a time, shows dramatically different outcomes based on how quickly restrictions are lifted.

Deaths from the virus in Massachusetts could remain below 5,000 at summer’s end if residents continue staying home through August, according to the COVID-19 Simulator, but might rise to 10 times that if the state suddenly relaxed its guidance to stay home and avoid gatherings.

On Monday, as the state’s death toll from the virus surpassed 3,000, Governor Charlie Baker said he will announce later this week whether he’ll extend the state’s stay-at-home advisory past its current expiration date of May 4. Baker didn’t say what he is planning, but he stressed that Massachusetts has been much harder hit by the pandemic than many other states, including those that have begun allowing some nonessential business to reopen.

Boston Mayor Martin J. Walsh, at a separate news conference Monday, was unequivocal.

“Boston will not reopen on May 4,” he said.

Maintaining current restrictions is projected to keep new infections trending downward through the summer, reaching single digits in late July, according to the simulator.

Tightening restrictions so that Massachusetts has a full lockdown, with interstate travel banned, could reduce deaths somewhat, bringing them down to 4,430 on Aug. 31, according to the simulator.

In a scenario in which current restrictions are lifted May 25 and the state switches to “minimal restrictions” through the summer, deaths from the virus are projected to begin ticking steeply upward in mid-July and reach 27,200 by Aug. 31. That strategy could also see a steep rise in new infections that would crest around Aug. 7, according to the simulator.

Nationally, the simulator predicts a death toll of 86,000 by the end of summer if current restrictions remain in place. In that scenario, new infections would decline into triple digits in mid-June and then into double digits by mid-July.