Some 2% of Covid-19 tests are coming back positive, compared with more than 13% during the height of the winter surge, according to Johns Hopkins University, which compiles Covid-19 testing and case data in the U.S.

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‘It’s a true reflection of a decrease in overall [Covid-19] circulation in the U.S.’
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The percentage of tests that come back positive, known as the test-positivity rate, depends both on the level of disease and the amount of testing being done. The national positivity rate was highest early in the pandemic, when the limited amount of testing available focused on people with symptoms.

The proportion of tests coming back positive has been consistently falling since April this year and is now at the lowest point since March 2020, the furthest back the Johns Hopkins data are available.

The low positivity rate is a signal that the drop in infections is really due to less disease in the country rather than because the U.S. is testing less for the virus, according to epidemiologists. It is another indication of how the U.S. is gaining ground against the Covid-19 pandemic, along with declining case counts, hospitalizations and deaths.

“It’s a true reflection of a decrease in overall circulation in the U.S.,” said

Anne Rimoin,

an infectious-disease epidemiologist at the UCLA Fielding School of Public Health. “But we still do have pockets where we’re seeing transmission of the virus, and we need to be careful.”

On June 10, the seven-day average of daily new Covid-19 cases in the U.S. was just over 13,800, according to the CDC, and average deaths were 352 a day.

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Public-health experts anticipated a drop in testing demand as infections, hospitalizations and deaths declined. Fewer infections translate into fewer patients and close contacts that need to be tested.

Also, the CDC’s current guidance says that vaccinated people without symptoms don’t need to be tested if they have come into contact with someone diagnosed with Covid-19 or undergo regular screening, with some exceptions.

“As infections drop and vaccinations increase, the need to conduct screening tests will decline,” said

Jennifer Nuzzo,

a senior scholar at the Johns Hopkins Center for Health Security and lead epidemiologist for the university’s Covid-19 testing insights initiative.

Dr. Nuzzo and other infectious-disease experts said testing remains an important tool for tracking the pandemic and curbing transmission.

People should keep being tested, health experts said, if they have symptoms or are unvaccinated. Nursing homes, prisons and other high-risk settings should probably continue to test people regularly, the experts said, particularly in areas with low vaccination rates or high infection levels.

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Some public-health experts expressed concern that people might not seek testing, even with mild symptoms, if they feel the pandemic is over or don’t see it as a threat, which could help spread the virus and complicate the ability of health authorities to keep track of the pandemic.

“Waiting until hospitalization rates rise is too late,” said

Leana Wen,

an emergency physician at the Milken Institute School of Public Health at George Washington University and a former Baltimore health commissioner.

“In areas with higher vaccination rates, I’m less concerned,” she added.

Throughout the pandemic, public-health officials have used the test-positivity rate to help gauge whether enough testing was being done to catch the majority of Covid-19 cases. If test positivity is high, it is likely that some cases are being missed.

At least five states had test-positivity rates of 40% or above in early January during the pandemic’s deadliest surge in the country. Now just three states—Idaho, Kansas and Alabama—have rates above 10%, according to Johns Hopkins University.

Health authorities have also used the metric to help suss out whether Covid-19 was spreading or retreating in a community.

Darlene Bhavnani,

an infectious-disease epidemiologist at the University of Texas, Austin, expressed caution about leaning too heavily on test positivity to gauge Covid-19 spread as results can depend on who in the community is being tested, which changes over time.

Other caveats: States often track test results in different ways, and the federal tally of tests includes only those analyzed at laboratories and is missing the rapid tests now being taken outside labs, including at home. At-home rapid tests started becoming widely available at pharmacies and retailers in April.

Write to Brianna Abbott at [email protected]