A medical professional worked in a tent at Somerville Hospital, where patients can drive up, be interviewed, and tested by staff for coronavirus infection. David L. Ryan/Globe Staff

People are losing their jobs, way of life, and grip on their sanity over the drastic social distancing measures ordered to curb the spread of the coronavirus pandemic. Yet the number of cases and deaths are on the rise, and infectious disease specialists warn that the worst is yet to come, creating a public health crisis that could overwhelm the medical system.

At the moment, signs of progress are hard to see, perhaps because there may not be any just yet. But in the weeks and months to come, as measures to curb the pandemic take hold, exacting untold economic and social harm, what will progress look like? What milestones will experts use to measure gains, however incremental, and to ever-so-warily hypothesize when we might return to some semblance of normalcy?

“That’s one of the hardest questions to answer in epidemiology, and it’s one of the things that everybody is most interested in,” said Samuel Scarpino, an epidemiologist at Northeastern University. “We’re going to have to be very cautious because we don’t want to waste all the sacrifices that we’ve already made.”

The first sign that the tide has started to turn, scientists say, will be a decline in new cases over several consecutive weeks, even as testing expands. In Boston, that peak is likely at least a few weeks away, Scarpino said. New coronavirus-related hospitalizations should fall a week or two after the number of new cases declines, in light of the time it takes for the disease to progress.

That would indicate that the economically devastating social distancing measures are working. Even then, it will be too soon to fully return to normal, specialists say. Just because there was a peak doesn’t mean it was the peak.

In fact, once new infections fall to a level that hospitals can manage, experts predict different regions will still experience a series of peaks and valleys in virus caseloads until a vaccine can be developed, something that will likely take at least 12 to 18 months. If social distancing restrictions are relaxed, governments will have to weigh economic against public health consequences in determining when, or whether, to reimpose them.

“What we’re doing right now is definitely worth it,” said Alex Perkins, an epidemiologist at the University of Notre Dame studying the trajectory of the pandemic. “Hopefully we’ll start to see some benefits, but we also have to recognize that we’re going to have to continue to adapt to this situation for the foreseeable future."

To reduce deaths by at least hundreds of thousands, top infectious disease specialists at Imperial College London recently projected that the United States should expect to have rolling periods of social distancing and school closures through late 2021. In each period, the measures would last about two months, relax for one month, then resume for two more. The specialists suggested using the number of coronavirus patients in intensive-care unit beds, based on the country’s peak intensive care unit capacity, as a trigger for restarting the restrictions.

For example, the Imperial College model projected that 510,000 people would die in two years in Great Britain without action. But the death toll would fall to 39,000 if the social distancing measures restarted every time the patient count in ICUs hit 400, or could shrink to 8,700 deaths if the trigger were 60 ICU patients.

The United States would see proportionally similar results, the specialists said, projecting that if the US did nothing, at least 2.2 million Americans would die.

A new report shows how a strategy to save potentially millions of lives in Great Britain and the United States could result in social distancing measures being imposed for two-thirds of the time through late 2021. The blue rectangles show the time spent social distancing and school closures, triggered by coronavirus ICU hospitalizations, in orange. This chart is for Great Britain, but the model is similar for the United States, the researchers wrote. Imperial College London COVID-19 Response Team (custom credit)/Imperial College London COVID-19 Response Team

Complicating projections is how much there is still to learn about the virus. For example, scientists aren’t sure how long immunity from the virus lasts in people who recover.

During the Spanish flu epidemic in 1918-1919, the last time the world confronted a pandemic of this scale, the impact of social distancing was clear. Philadelphia held a World War I victory parade and saw 10,000 deaths in the following month, while in St. Louis, which had canceled its parade, the death toll did not exceed 700, according to the US Centers for Disease Control and Prevention.

Another important milestone would be for America’s testing capacity to advance to the point of being able to quickly identify and isolate coronavirus patients and their contacts, including household members. That may require bolstering local health departments, Perkins said.

“We’d like to get to where it’s a more manageable thing,” Perkins said. “We’re not anywhere near that right now.”

Through extremely restrictive social distancing measures and far more testing, other countries have shown it’s possible to control the virus.

On Thursday, China announced its first day with no new locally transmitted cases. That was a bright spot for many epidemiologists who have watched Italy’s hospitals become overwhelmed and deaths in that country surpass China’s roughly 3,200.

But getting the virus under control in China took draconian measures that tanked both the economy and civil liberties, as many non-infected citizens weren’t allowed to leave their homes and coronavirus patients were required to be hospitalized despite not needing hospital care. Now, China is reopening factories and businesses but has implemented thermometer scans at the entrances to many buildings. Many schools are still closed.

It’s unclear whether democratic societies would tolerate such measures.

“China’s response was extreme by US standards, but it seems to have worked" at least in the short term, said Nadia Abuelezam, a Boston College epidemiologist.

In Singapore, Taiwan, Hong Kong, and South Korea, governments managed to keep case numbers relatively low through large-scale testing that allowed for people with infections to be identified and quarantined.

Epidemiologists would welcome any news about increased testing capabilities to ensure that anyone with symptoms could receive a test. Currently, many sick people have complained that they were denied tests due to a shortage and strict rules that have limited tests except for those with links to a confirmed case or foreign travel.

Until testing capacity is up, epidemiologists said, the numbers do not offer a true measure of the outbreak because they’re just showing that more people are being tested. Researchers believe the state’s confirmed case count — 525 on Saturday — represents a fraction of the actual number of infections.

“We don’t have enough data now to know where we are on the epidemic curve because we simply aren’t testing enough," Abuelezam said.

Elizabeth Halloran, a senior researcher at the Fred Hutchinson Cancer Research Center in Seattle, said it’s crucial that the US boost its testing capacity even for people with mild or no symptoms. Studies show that undetected cases drive the growth in epidemics as people who don’t feel severely ill often continue to go about life, infecting those they interact with.

Experts would also celebrate any innovations that can increase the availability of ventilators or hospital capacity. But true long-term progress won’t come until either drugs or a vaccine are developed and mass-produced.

Vaccines are ideal because they prevent infections and establish immunity among a large population of people, Perkins said, but they’re also extremely difficult to create. Many infectious diseases still lack a vaccine. Clinical trials are underway for coronavirus vaccines.

“There’s so much of this across the world right now, it’s a disease that’s likely going to be with us for the foreseeable future,” Perkins said, noting that smallpox is the only infectious disease that has been successfully eradicated. “Getting all the way to zero is incredibly difficult.”

Drugs could likely come along sooner and would be hugely important in saving lives. Massachusetts General Hospital and Brigham and Women’s Hospital are enrolling patients in studies of the experimental drug remdesivir. Scientists hope that a drug could be used to prevent new infections as well as treat them.

Abuelezam said she did see two potential bright spots. She hopes this terrifying episode will lead nations to prioritize epidemic preparedness in the future. Many deaths from the pandemic could have been prevented with better monitoring and action, she said.

She also hopes the tragedy will unify people in common cause by showing how our fates are intertwined.