Mass. is putting a lot of focus on its coronavirus testing strategy. Will it work?

Stanley Street Treatment and Resources in Fall River is one of 18 community health centers to expand COVID-19 testing capacity.Barry Chin/Globe Staff/The Boston Globe

After weeks of racing to keep pace with infections, Governor Charlie Baker recently announced plans to drastically expand the state’s testing capacity to diagnose new cases of the coronavirus.

But his goal to more than triple the current number of daily tests by the end of July and increase it at least fivefold by December may come too late to make a significant difference in containing the virus’s spread, some epidemiologists say. It is both a more aggressive testing plan than most states have mustered, and also perhaps no match for the rampant virus.

“It’s like a dog chasing its tail,” said Dr. Michael Mina, an assistant professor of epidemiology at the Harvard T. H. Chan School of Public Health. “You’re constantly behind.”

The state has already tested more than 500,000 people, and Massachusetts now has among the highest per capita testing rates in the nation, trailing only Rhode Island, New York, and North Dakota. But residents may have to be tested multiple times as society reopens and the risk of infection rises.

With more testing kits becoming available, and an enlarged capacity to perform the tests at labs throughout Massachusetts, Mina and other infectious disease specialists say the state has the ability to ramp up testing substantially in the next two months. To reach Baker’s goal of the state having the ability to test 45,000 people a day within 10 weeks, it will have to do much more to expand capacity.

In recent weeks, the number of daily tests has plateaued at about 13,000, mainly because of the strict criteria of who could be tested and the limited availability of tests. And this week, the number of daily tests appears to have declined substantially.

Mina, who has played a significant role by working with private labs to boost the state’s ability to test for the virus, worries that Massachusetts is so far behind that the governor’s plan may be a waste of resources.

Other epidemiologists, however, said ramping up testing remains critical to blunting the spread of the virus.

“For every person we can identify as infected before they transmit the virus to a new person, it will break the transmission chain and lower the overall spread of the disease,” said Erin Bromage, a biology professor who studies infectious diseases at the University of Massachusetts Dartmouth

Baker’s plan is based on estimates there will be more than 4,000 new infections every day in July, and that an average of 10 people for every positive case will have to be tested — thus, the 45,000 test goal. In addition, it calls for identifying the contacts of those infected and isolating them until they’ve tested negative.

But with so many infections, such a system is unlikely to contain the virus, Mina said. Those challenges are likely to be compounded as the shutdown gradually eases, and more people travel to Massachusetts from states with less testing and fewer restrictions.

“This virus just moves too fast,” said Mina, who’s also associate medical director of the clinical microbiology laboratory at Brigham and Women’s Hospital. “The moment you start contact tracing, you’re behind the curve.”

State public health officials, however, say testing, tracing, and isolation are key to halting the spread of the virus.

The plan includes expanded eligibility for tests including those with mild symptoms; distributing more nasal swabs and plastic tubes to conduct tests; and creating more testing sites and lab space at everywhere from pharmacies to universities.

“Diagnostic testing … with prompt contact tracing is a very important part of the risk reduction strategy in Massachusetts, in conjunction with guidance, such as social distancing, masking, hand washing, staying at home, and all the other measures that have been implemented,” Dr. Catherine Brown, the state’s epidemiologist, said in a statement.

Dr. Thomas Tsai, a health policy researcher at the Harvard Global Health Institute, said the state must ensure that testing and tracing is part of a larger effort to stem the spread of the disease, which includes widespread wearing of facemasks. The tracing effort alone will cost the state at least $44 million.

Among the challenges are how quickly contacts can be found, whether they’re tested at a time when the virus can be detected, and how long it takes for the results of the tests.

If it takes too long to identify people who were exposed, the system would do little to contain the disease.

“A half-built dike won’t hold back the water,” Tsai said. “The system has to be rapid, timely, and done at a wide scale.”

While testing and tracing may work better on diseases, such as Ebola, that don’t spread as swiftly and easily as COVID-19, the system doesn’t have to be perfect to have benefits, he and others said.

The system could work in smaller settings, such as at prisons and nursing homes. It will also provide a means of testing more asymptomatic people, who can spread the virus without knowing.

One reason the number of tests in Massachusetts has plateaued in recent weeks was an inability to extend a large number of tests to those who lack symptoms, epidemiologists say. With limited testing available, only those who had clear symptoms were eligible.

As many as 80 percent of people who contract COVID-19 are either asymptomatic or develop mild symptoms, according to the World Health Organization.

“These efforts will hopefully allow us to avoid returning to the blunt instrument of community quarantine, and instead enable us to respond commensurately to the virus, with smaller quarantines where needed,” said Yonatan Grad, assistant professor of immunology and infectious diseases at the Harvard’s Chan School.

At the Broad Institute of MIT and Harvard, which can now process more than 25,000 tests a day, officials said the governor’s plan appears to be a viable path forward to allow society to begin reopening without a vaccine.

“Only by testing many more people — whether they have symptoms or not — can we cut off all these transmissions,” said David Cameron, a spokesman for the Broad Institute, which expects to increase its testing capacity further in the coming weeks. “Otherwise, we are flying blind.”

Dr. David Hamer, an infectious disease specialist at Boston Medical Center, said that new technology may help accelerate the tracing process, such as using cellphone apps that alert the potentially infected to get tested.

And if the amount of new infections continues to decline, that could make the state’s plan more viable.

“It will work better if the numbers of new cases are much lower than they are now,” he said.

But Mina said the state would be better off expanding serology tests, which detect antibodies produced in response to COVID-19. Baker’s testing goals remain exclusively for diagnosing new infections.

The state could also ramp up other surveillance techniques, such as monitoring the amount of the disease in sewage, he said. Recent studies suggest that stool samples from waste water treatment plants could provide a more accurate picture of the extent of the disease than clinical testing alone.

While Mina acknowledged that some serology tests have been marred by inaccurate results, the information remains valuable, as the presence of even small amounts of antibodies would alert public health officials to the presence of the virus, he said.

“These tests are cheaper, easier, and they help you find outbreaks,” Mina said of the antibody tests. “Capturing a picture of everyone with virus isn’t working.”