Coronavirus temperature scans are nothing more than pandemic security theater. In some cases, they're dangerous.

• Public thermometer scans for COVID-19, the disease caused by the coronavirus, are not only useless but also may be fueling the virus' spread.
• On-the-go temperature checks are wildly inaccurate. Also, not everyone with COVID-19 has a fever, so such temperature readings may lull people into a false sense of security.
• The scans are done out in public, when sick people have already been exposing others.
• A better idea is monitoring temperatures across a population, using at-home thermometer readings to track where illnesses may be spreading. One smart-thermometer company, Kinsa, is already doing this and seeing some success.

Dr. Anthony Fauci has gotten his temperature taken a lot during the pandemic. The results have not been stellar.

On one occasion, his temperature registered at 103 degrees Fahrenheit in the summer heat of Washington, DC, before he rechecked it later in his air-conditioned car (he was fine at 97.4). Later, his heat reading came up as 93 degrees Fahrenheit in a chilly indoor space, "which means I should've been on a respirator," he told Dr. Jason Blaylock, the chief of medicine at Walter Reed Medical Center, during their virtual grand rounds last week.

"This is going to disappoint a lot of people," Fauci told Blaylock. "The benefit is marginal."

Temperature checks have been so inconsistent and needlessly time-consuming during the pandemic that Fauci doesn't even get his checked anymore before he heads into the White House or the National Institutes of Health, where he works.

Yet handheld thermometers have become ubiquitous coronavirus-tracking tools anyway, and they are widely used in public locations like salons, offices, schools, and airports.

The move is just as needless and arbitrary as removing your shoes before boarding a flight.

Thermometer screenings for COVID-19 aren't just inaccurate and unhelpful, they're lulling people into a false sense of security during the pandemic. A person's temperature, even when taken accurately, isn't always an indication of early coronavirus infection and often won't tell you that someone is ill when they're at their most contagious stage.

Ultimately, public thermometer screenings are a dangerous piece of pandemic security theater that could be encouraging people to hang out in close confines at the exact moments when they really shouldn't be.

"If your objective is to screen people out who are arriving at a lobby or entry point, it's mostly theater," Inder Singh, the CEO of the smart-thermometer company Kinsa, said. "These kinds of high-throughput situations are rife with errors. Very frankly, by the time you're screening people out, it's too late."

Instead, thermometers should be one of many coronavirus protection protocols but used before people go out in public and expose others to their germs.

Many coronavirus patients don't run a fever

The first couple days of a COVID-19 illness, when a person is at their most infectious, often don't include a fever. This is why people around the world have gotten sick after attending gatherings at bars, nightclubs, churches, and nursing homes.

"You could be in the restaurant, feeling perfectly well, and start to get a fever," Mike Ryan, the World Health Organization's executive director of health emergencies, said in June. "It's because the disease can spread at that moment that the disease is so contagious."

Even those who do display a fever early on often have a moderate low-grade temperature that is barely detectable, below 100 degrees Fahrenheit. Some patients never develop clear symptoms of infection at all.

Temperature measurements could miss more than half of all infected people, the US Food and Drug Administration said in June.

One hospital in Melbourne, Australia, took the temperatures of 34 people who tested positive for COVID-19 from March through May and found that a fever was present only about 20% of the time.

In the most critical hours for quarantining people with the coronavirus then, thermometers may not pick up much amiss. But there's another reason that they're so dangerous.

"By the time you take someone's temperature in the lobby, or in the school entryway, it's too late," Singh said. "They've already spread the disease. They were already on public transportation. They were already standing in a lobby with others."

Thermometers need to be used in conjunction with other virus-fighting tools, and preferably at home

Thermometers should instead be one at-home tool used to stop the coronavirus. They need to be used alongside masks, contact tracing, social distancing, and quarantining sick and exposed people.

None of these public-health measures will be 100% effective at stamping out the virus on their own, but put some of them together, and they'll do pretty well at stopping infections, as countries like Japan and France have seen.

Singh said Kinsa has found its at-home smart-thermometer network can be used as an early-warning system to see where contagious illnesses like the coronavirus and the flu are spreading in schools, workplaces, cities, and states around the US.

In places where people have used Kinsa's thermometers consistently, checking their temperatures at home every day, the company has been able to effectively forecast outbreaks of both the coronavirus and the flu, noticing fever spikes weeks before hospitals and clinics start to see an influx of patients.

So while a thermometer reading is generally not useful when taken on a lone shopper, worker, or traveler, in the aggregate it can help create a local forecast of where a disease might spread next.

Using populationwide temperature readings to develop a local illness forecast can help people ramp up their other virus-fighting tricks

There's plenty of data to support the idea that public temperature screenings for COVID-19 are pure theater.

As early as February 23, the Centers for Disease Control and Prevention had screened over 46,000 travelers coming into the US from China, hoping to catch the disease as it hit American borders. Of those tens of thousands of people checked for fevers, only one was plucked out who later tested positive for the coronavirus.

Clearly, the virus found many other ways to get around the US.

The CDC doesn't even mention fevers or temperature screenings in the guidance it gives out to travelers arriving in the US from "high-risk" countries, instead extolling the virtues of hand hygiene and staying away from people who are sick.

Fauci now advocates that people screening others entering public spaces "ask questions" about how they are feeling instead of doing temperature scans. It's a reminder there's no silver bullet for avoiding virus spread, no matter how comforting pandemic security theater may feel.