How You’ll Know When the Pandemic Is Contained

There will be no dramatic end to the pandemic, but we can at least look for these four signs that it’s under control

Photo: San Francisco Chronicle/Hearst Newspapers/Getty Images

After a dark, lonely winter — when cases of Covid-19 ravaged the globe, surpassing 2 million deaths in mid-January, and with new variants cropping up — we seem to have begun emerging from the absolute worst. Spring’s fate is up in the air, but the ramped-up vaccine program under the new administration is sending hopeful signals. Seeing more and more friends and family posting vaccine selfies on social media amid climbing vaccination rates makes the end of the pandemic feel a little more tangible, in some ways.

But when we say “the end,” what exactly do we mean?

Its challenging to know when a pandemic will be over, because by definition, a pandemic is an epidemic occurring on multiple continents. Covid-19 may be on the downslope of wreaking havoc in the United States, but what about elsewhere?

Experts caution that there likely won’t be a complete end to Covid-19: Sporadic, small outbreaks may continue around the world. And even getting to that point is not on the fast track.

“The pandemic is not going to end in a bang; it’s going to end in a whimper,” says Syra Madad, an infectious disease epidemiologist at New York City Health + Hospitals, and “getting to Covid zero is unrealistic.” But the world can fall below epidemic levels of the virus as it fades into the background.

If we can accept that Covid is here to stay, how do we make it like other infectious diseases that we just live with fairly safely? Experts say that the best way to think about Covid-19 might be to think about when we will have contained it. They cite four benchmarks that could signal that containment.

Extremely low caseloads

One sign that we may have entered pandemic containment is if caseloads fall below two to four per 100,000 people, says Jessica Malaty Rivera, an infectious disease epidemiologist at the The Atlantic’s Covid Tracking Project. Currently, most U.S. states still have moderate (10 to 50 cases per 100,000) to high (more than 100 cases per 100,000 people) levels of transmission, according to data from the U.S. Centers for Disease Control and Prevention. Crystal Watson, a health security researcher at Johns Hopkins University, offers an even more conservative threshold of 0.5 cases per 100,000 people per day.

“If that translates to 2,000 cases a day, that’s very low transmission for a population of 330 million,” says Rivera. At that level, cases would be so low that contact tracers would no longer be overwhelmed by positive cases. In this situation, Madad says they would have adequate time and resources to reach out to an affected individual’s close contacts to urge isolation and halt the spread of disease.

If we can accept that Covid is here to stay, how do we make it like other infectious diseases that we just live with fairly safely?

Fewer than 100 deaths a day nationally

A threshold of 100 Covid-related deaths a day would approach the average for flu, says Rivera. Falling below that threshold means less stress on the health care infrastructure and frontline healthcare workers who have been doing battle against Covid-19. As a caveat, Rivera cautions that the comparison of Covid-19 to flu isn’t perfect because deaths from Covid are more likely to be accurately reported than are flu-related deaths. In any case, as of early March 2021, Covid-19 deaths still exceeded 1,700 a day in the United States.

Low percent positivity rates with robust testing

The positivity rate for Covid-19 refers to the percentage of all Covid-19 tests that are positive and helps determine the level of transmission in a community. Experts say that low percent positivity rates of 1% to 2% are a sign of containment.

Accurate positivity rates, however, rely on testing and the reporting of testing results to public health officials. “Testing shouldn’t basically be gone if we think Covid-19 is no longer a threat,” notes Madad.

Rivera says that even though the United States rolled out vaccines quickly, testing rates haven’t really improved over the last year. “The plateaus that we’ve seen in testing have been deeply frustrating,” she says. “Are people getting reinfected? Are more cases happening? Is the variant escaping vaccination? Testing would be able to answer some of these questions.”

Reaching an immunization uptake threshold

It’s difficult to know how much of the population needs to be vaccinated for transmission of the virus to decrease to containment levels. But experts believe that a vaccination rate higher than 70% will likely move a population toward herd immunity. Anthony Fauci, MD, director of the National Institute of Allergy and Infectious Diseases, has said that reaching herd immunity may require vaccinating 70% to 85% of the U.S. population.

The various common infectious diseases require different levels of immunization to reduce transmission. The measles virus, for instance, is highly infectious and lingers in the air for hours. With measles, if vaccination rates drop below 90%, says Rivera, we start seeing outbreaks. “That’s not the case with Covid,” she explains. “It doesn’t linger in the air like measles for several hours, and it probably doesn’t need a threshold of 90% or more.”

But the level of vaccination to achieve herd immunity for Covid-19 is still not thoroughly established. “Covid-19 is cruel in that way — it truly is novel and not like other diseases we’ve dealt with,” says Rivera.

Someday, though, it will no longer be novel. As case numbers and percent positive rates drop to certain thresholds, and vaccination rates increase, communities will be better off. This combination of factors rather than a single metric will signify containment, says Rivera, indicating that the pandemic is at least approaching a whimpering exit.