Is Mass. heading for a third coronavirus surge? These charts show why experts are worried

At Torre Unidad housing in Boston, Shuiying Cheung-Ma, 75, gets the COVID-19 vaccine shot from Sofie Ghitman, a BSN nursing student, on March 19.David L. Ryan/Globe Staff

Coronavirus case counts and other metrics are on the rise, sending worrisome signals about a possible third surge of the deadly virus in Massachusetts.

The seven-day average of reported cases, which hovered at just over 1,300 in early March, has now climbed to over 2,000. Hospitalizations, which tend to follow a surge in cases, have begun to tick up again. Test positivity rates are also on the rise, reaching 4.2 percent statewide when college testing programs are factored out.

“It looks to me like we’re very much entering into another surge,” Northeastern University epidemiologist Samuel Scarpino said this week.

At the same time, Scarpino said, this surge may not be as bad as the two previous ones, which hit last spring and last fall. Factors working in our favor include a rising level of vaccinations, especially among older residents and vulnerable populations, and the protection ramping up in the systems of those vaccinated weeks ago, he said.

“While the cases are going up, we’re also building up immunity,” he said. “We’re entering into a surge of immunity.”

Another factor that could help the state, experts say, is that younger people, who tend to get less severe illness from the virus, are making up a greater proportion of those infected.

Dr. Howard Koh, a professor at the Harvard T.H. Chan School of Public Health and a former top Obama administration public health official, said, “We may well be poised to enter a third surge in our state, which would be so demoralizing and potentially devastating.”

The warnings about Massachusetts come as officials and experts have been cautioning about the possibility of a fourth surge nationally fueled by fast-spreading coronavirus variants and aided by people letting down their guard. (A new surge would be Massachusetts’ third surge because the state avoided a surge that hit much of the rest of the country last summer.)

Nationally, the seven-day average of coronavirus cases is slightly above 62,000 cases per day, CDC Director Rochelle Walensky said at a briefing Friday, a number that’s up from the low 50,000s in mid-March. New hospitalizations also continue to increase, she said.

The data were clear, she added, that despite progress in vaccinations, the country remained in a “pivotal” moment and “we simply cannot yet afford to relax the prevention strategies” such as wearing a mask and social distancing.

Here’s a look at some of the key metrics that have people concerned about Massachusetts:

CASES

The seven-day average of confirmed coronavirus cases plummeted from a high of 6,120 on Jan. 12 to 1,311 on March 10. But it has now been rising for about three weeks.

HOSPITALIZATIONS

The single-day tally of hospitalized coronavirus patients dropped from a high of 2,428 on Jan 4 to a low of 580 on March 20. But it has now generally been rising for the past two weeks. Hospitalization figures tend to lag behind case figures. Scarpino said the expectation is that hospitalization rates will be lower because of vaccinations, but he noted that the current level of hospitalizations is higher than when the surge began last fall.

DEATHS

The seven-day average of confirmed coronavirus deaths dropped from 86 on Jan. 6 to 30 on March 18, then ticked up and down. In recent days, the numbers have edged downward again, to 29. But as more people become hospitalized, will these numbers head back up?

HIGH-RISK COMMUNITIES

The number of Massachusetts communities deemed at high risk from coronavirus has risen to 55 from 32 last week and just 20 the week before. The categorization is based on a combination of cases per 100,000 residents and test positivity rates over a two-week period. For towns below 10,000 people, the criteria for being high-risk is simply 25 total cases.

CASES IN SCHOOLS

Weekly reports of coronavirus cases among students and staff in schools have been generally on the rise since the end of February, when pool testing began in hundreds of schools. The latest report showed the highest weekly total since the start of the academic year.

Koh, who is also a former Massachusetts public health commissioner, said he felt it was too early to declare the state was in a surge because the state hadn’t yet seen “an irrefutable, sustained rise in disease burden as reflected by increased cases, test positivity rates, hospitalizations, and eventually deaths.”

But he said, “At the very least, the previous rapid drop in cases, hospitalizations, and deaths has ended abruptly, which is not what anyone wants to see.”

He said officials needed to keep a close eye on the trends. “In the meantime, we need to continue to accelerate vaccinations, monitor the dynamics of the variants, and continue all prevention measures until further notice,” Koh said.

“We are still running a public health marathon and we can’t quit with the finish line in sight,” he said.

Peter Bailey-Wells of the Globe staff contributed to this report.