No, a Negative Coronavirus Test Does Not Mean You Can Safely Socialize
A negative test is helpful, scientists and doctors say.
But it doesn’t mean you should skip other measures, like quarantining, masking and distancing.
In the lead-up to Thanksgiving, Americans are no stranger to planning. But this year, as they prepare to let turkeys brine and pie crusts thaw, people across the country are waiting for something extra: a coronavirus test they hope can clear them to mingle with loved ones.
Many people consider a negative coronavirus test to be a ticket to freely socialize without precautions. But scientists and doctors say this is dangerously misguided. It is one precautionary measure but does not negate the need for others, like quarantining, masking and distancing.
The main reason is that a test gives information about the level of the virus at one point in time. A person could be infected but not have enough virus yet for it to register on a test.
Or, a person may become infected in the hours or days after taking a test.
“If you require all of your guests to email you a negative test result before your Thanksgiving dinner, it will definitely decrease the risk of an outbreak — but not completely,” said Dr. KJ Seung, chief of strategy and policy for the Covid response at Partners in Health. Yet this is a common misperception contact tracers hear when talking to people, he said.
The experts agreed that tests were very useful for one thing: If someone receives a positive test, that person knows to stay home and isolate.
But a negative test, while helpful, is not sufficient, said Dr. Esther Choo, an emergency medicine physician and a professor at Oregon Health and Science University.
A test “filters out those who are positive and definitely shouldn’t be there,” she said. “Testing negative basically changes nothing about behavior. It still means wear a mask, distance, avoid indoors if you can.”
Not all tests are created equal.
- Different tests for the coronavirus give different information.
- Laboratory tests that rely on a technique called polymerase chain reaction, or P.C.R., can detect the virus when it’s present even at very low levels.
- Antigen tests are faster, less expensive and more convenient — they can deliver results in a matter of minutes — but are also more prone to missing the virus when it’s scarce.
- To receive emergency authorization from the Food and Drug Administration, antigen tests for the coronavirus need to detect only 80 percent of the infections found by P.C.R.
A person who tests negative with an antigen test might test positive by P.C.R. — raising the risk that a negative antigen test could give someone a false sense of security en route to Thanksgiving dinner, said Paige Larkin, a clinical microbiologist at NorthShore University HealthSystem in Chicago, where she specializes in infectious disease diagnostics.
Taking multiple tests over a period of days gives a clearer answer.
But experts cautioned that no test — regardless of how many times it’s taken in succession — can definitively determine whether someone infected by the coronavirus is contagious, or no longer poses a transmission risk to other people.
The October outbreak at the White House is a good example of what can happen when a group of people rely heavily on testing and ignore other strategies to limit the spread of the virus.
Dr. Anthony S. Fauci, the nation’s top infectious disease expert, said in a New York Times interview with Elisabeth Rosenthal that he will not be seeing his three adult daughters this Thanksgiving.
Dr. Michael Mina, an epidemiologist and immunologist at Harvard, said that people could combine a negative test with a two-week quarantine.
Avoiding any contact with other people for a week or more before taking a test is a powerful tool, said Jeffrey Townsend, a professor of biostatistics at the Yale School of Public Health.
Not only does it decrease exposure, but it also gives the virus more opportunity to reach detectable levels in infected people, his research has found.
“You can do more quarantine, and it is quite helpful,” he said. “But the test on exit really helps, and it really drops your chance.”
https://www.nytimes.com/2020/11/21/upshot/coronavirus-test-thanksgiving-plans.html