Medical Examiner

What Is the Point of Temperature Checks?

These really only work if the rest of the system is working. In America it is not.

A gloved hand holds a thermometer to the forehead of a girl who is wearing a mask.
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In the coming weeks, months, years (eternity … ?), you might have to get your temperature taken at various junctures as you go about your routine outside your home. Apple, for example, announced this week that it will conduct temperature checks at the doors of its stores as they reopen. The TSA is considering temperature checks at airports, as is the CEO of Snap for the company’s offices. The thermal camera business is booming.

You might have some questions about how this will all work! We’re here to help.

What happens if I get a temperature check and it turns out I have a fever?

Not much. At least, there aren’t any temperature police who will come and arrest you for being out while sick or anything like that. At most, you’ll be asked not to shop. “Anyone with a fever will be kindly asked to rest at home and contact their health-care provider,” the CEO of Canadian supermarket chain T&T told the Toronto Star. Another important point from that story: Temperature checks at T&T supermarkets are voluntary for customers. Whether or not to do temperature checks, and how to enforce them, is, so far, left up to stores. Whether an individual who has a high temperature heads home or simply proceeds to a different place to shop is left up to the individual. This variability means it is likely that temperature screenings will play out differently in different areas of the U.S., and among different demographics.

Will temperature checks definitely catch people with the coronavirus? What about people who have the virus but no symptoms?

This is exactly the problem. Temperature checks would miss anyone who does not have symptoms or, in particular, this symptom. Exactly how often a coronavirus infection comes with a fever is still slightly unclear, but what is certain is that it is possible to be sick with COVID-19 and not have a fever. It’s even more likely that you wouldn’t have a fever for the duration of the infection. A case study of 5,700 patients hospitalized for COVID-19 in the New York City area published in JAMA found that just over 30 percent of patients had a fever when they came in, which caused experts to question the utility of temperature checks at all. There’s also the smaller issue that temperature checks will catch people who are running a fever for another reason (but if you have some other infection, it’s good to not be spreading that right now too).

Another problem with temperature checks: The thermal cameras that some business and airports are using to scan temperatures aren’t as accurate as individual thermometers are, meaning they’re imperfect filters even for people with fevers. Drones have the same problem.

If you have a fever, how are you supposed to know whether or not the fever is due to the coronavirus?

Well, you would need to get a test to confirm a coronavirus case, particularly if you don’t have other symptoms or a consistent fever. The problem is that failing a temperature check wouldn’t mean you’d automatically get a referral for a test, and even as testing capacity ramps up, getting one can still be hard.

So, temperature checks are sort of just security theater for the coronavirus era?

A little bit! Temperature checks really only stand to work as well as the rest of the system does. There are a number of ways people could respond to realizing they have a fever that would help, sure. Individuals could decide to avoid tasks like grocery store runs if they have symptoms. Employers who are making employees submit to temperature checks could give out paid sick days to employees who have fevers. Much like masks, temperature checks can be a useful tool to cut down on risk, a little bit. But they cannot be the only tool.

If you haven’t seen New York Times reporter Donald McNeil’s appearance on Rachel Maddow’s show (from March, when they were sitting across from each other!), it provides a very helpful breakdown on why widespread temperature checks are a viable strategy for China to combat the coronavirus but are less effective here. As McNeil explains, if you run a fever in China, you are sent to a fever clinic, where you are: tested for the coronavirus.

In the absence of that, temperature checks sure stand to provide a false sense of comfort and allow stores and the TSA to make a big show of protecting people without necessarily doing much. Imagine a system for driving in which we had stop signs but no traffic court. Actually, then also imagine that instead of risking plowing into someone else in the moment, the risk was that someone else got sick days later, and also you’d never personally hear about it. That’s temperature checks in the absence of testing and other meaningful measures to prevent the spread of the coronavirus. Not useless—surely many people would still carefully stop at stop signs in that scenario. Which is to say: It’s possible widespread temperature checks would serve as encouragement for people with fevers to stay home altogether.

Experts are mixed on the usefulness of temperature checks, which makes sense, because we’re going through an entirely new situation here. “I don’t think they’re a bad idea. I don’t think they’re counterproductive,” Charles Powell, CEO of the Mount Sinai–National Jewish Health Respiratory Institute, told Spectrum News NY1. “I think we just have to be cognizant of how we interpret it.” But other experts have expressed a deeper level of skepticism that they could be useful at all. We probably won’t know for sure how well they worked for a while; we’re still in the middle of the experiment here. Like with so much else in this pandemic, from mask-wearing to positive antibody tests, we have to be especially careful not to overinterpret them as being useful, or a reason to ease up on measures like social distancing. In other words, don’t take temperature checks as a reason to head to an Apple store for kicks. Conversely: If your local supermarket doesn’t have temperature checks, that’s not a reason to freak out.

Hmmm, this is complicated.

Yes, and to add one more complication: It’s unclear that we even have enough thermometers to do temperature checks consistently.