No, a negative coronavirus test doesn’t mean it’s safe to socialize

Looking ahead to Thanksgiving, Americans are no strangers to planning. But this year, as they prepare to let the turkey brine and pie crusts thaw, people across the country are waiting for something more: A coronavirus test they hope may inspire them to mingle with it. their relatives.

Many people see a negative coronavirus test as a ticket to socializing freely without precautions. But scientists and doctors say this is dangerously wrong. This is a precautionary measure, but does not remove the need for others, such as quarantining, masking, and distancing.

The main reason is that a test gives information about the level of the virus at a given time. A person can be infected but not yet have enough virus to register for a test. Or, a person can become infected within hours or days of a test. Additionally, the tests do not have 100% accuracy.

“If you ask all of your guests to email you a negative test result before your Thanksgiving dinner, it will certainly decrease the risk of an outbreak – but not completely,” said Dr. KJ Seung, chief of the strategy and policy for Covid’s response to Partners in Health. Yet, it’s a common misconception that contact tracers hear when talking to people, he said.

Experts agreed that the tests were very helpful for one thing: if someone tests positive, that person knows how to stay home and self-isolate. But a negative test, while helpful, isn’t enough, said Dr. Esther Choo, emergency physician and professor at the Oregon University of Health and Sciences.

A test “filters out those who are positive and definitely shouldn’t be there,” she says. “The negative test does not fundamentally change the behavior. This always means wearing a mask, keeping away, avoiding 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 PCR, can detect the virus when it is present even at very low levels. But it may take a few days to return the results, allowing time for someone to be exposed. Antigen testing is faster, cheaper, and more convenient – they can provide results in minutes – but are also more likely to miss the virus when it’s rare. To receive emergency clearance from the Food and Drug Administration, coronavirus antigen tests must only detect 80% of infections detected by PCR.Many rapid tests are also not allowed in people who do not have symptoms.

In some cases, a person who results in negative for an antigen test can be tested positive by PCR – increasing the risk that a negative antigen test could give someone a false sense of security on their way to Thanksgiving dinner, said Paige Larkin, clinical microbiologist at NorthShore University HealthSystem in Chicago, where she specializes in diagnosing infectious diseases.

Why testing alone is not enough

“A negative result is a snapshot in time,” said Dr. Larkin. “This tells you that the exact second you are tested the virus has not been detected. It does not mean that you are not infected. “

After entering a person’s body, it may take several days for the virus to build up, and in the meantime there may not be enough virus for a test to detect it. But the person could still be infected or contagious in the meantime. A person who tests negative one day can turn positive just a day or even an hour later. People can spread the virus in the days before the onset of illness and can also spread the virus even if they never develop symptoms.

“The challenge for the individual is then that a negative test today does not mean that a person will be negative tomorrow or the next day,” said Natalie Dean, assistant professor of biostatistics at the University of Florida.

Doing several tests over a period of several days gives a clearer answer. But experts have warned that no test – no matter how many times it is done in succession – can definitively determine whether a person infected with the coronavirus is contagious or no longer poses a risk of transmission 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.

In an informal survey of 670 epidemiologists, only 6% said if they recently tested negative for the virus, they would be comfortable spending time indoors with others without precautions. Twenty-nine percent said they would if everyone also used masks and kept their distance. And 64% of them said that even if they tested negative, they wouldn’t be comfortable spending time indoors with people they don’t live with.

How to think about risk

Yet it is often unrealistic to avoid others for months on end. People need to work and take care of their basic needs, and they also crave connection with family and friends. Risk is a spectrum, not a binary one, and there are ways to reduce it, the experts said.

“Don’t let the perfect be the enemy of the good,” said Dr. Anthony S. Fauci, the nation’s leading infectious disease specialist, in an interview with The New York Times with Elisabeth Rosenthal. “Your risk, if everyone is tested before you get together to sit down for dinner, is greatly reduced. It might never be zero, but, you know, we don’t live in a totally risk-free society. “

However, Dr. Fauci won’t be seeing his three adult daughters on Thanksgiving.

Dr Michael Mina, an epidemiologist and immunologist at Harvard, said that at this point in the pandemic, people could not be expected to completely eliminate the risk of coronavirus. He compared it to the risk of a car accident. To avoid risk, people did not rise at all in a car. Seat belts, airbags, and following the rules of the road all reduce the risk, but that doesn’t mean someone is completely safe – and people don’t give up using a seat belt just because the car has airbags. Coronavirus precautions such as testing, distancing, and masking work the same, he said.

How to reduce the risks and keep coming together

Before getting together with others, Dr Mina said, people could combine a negative test with a two-week quarantine if they were able, and have a frank conversation with older family members about the risk and whether they are prepared to attend. At a rally, he said, risk mitigation strategies might include keeping dinner short, holding the event outside, wearing a mask when you’re not eating, and hugging instead of touching.

Avoiding contact with other people for a week or more before taking a test is a powerful tool, said Jeffrey Townsend, professor of biostatistics at the Yale School of Public Health. Not only does this decrease exposure, but it also gives the virus more opportunities to reach detectable levels in those infected, according to its research.

“You can do more quarantine, and that’s very helpful,” he says. “But the exit test really helps, and it really sucks your luck.”

Professor Townsend will be celebrating Thanksgiving at home with his wife and children. Although he is studying testing protocols, he has never taken a coronavirus test himself, as he has stayed at home throughout the pandemic except for urgent needs.