Coronavirus FAQ: Folks At Trump-Biden Debate Were Scanned For Fever. Is That Helpful?

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A temperature check is conducted at a Trump campaign rally last month in Toledo, Ohio. / LightRocket via Getty Images

Each week we answer some of your pressing questions about the coronavirus and how to stay safe. Email us your questions at goatsandsoda@npr.org with the subject line "Weekly Coronavirus Questions."

More and more places want to take my temperature before letting me in, with some kind of device they aim at my head. What are the benefits — and drawbacks?

If you go out and about during this pandemic, you're probably going to get your temperature taken. Often.

At the dentist's office, at a gym or exercise class, even at some restaurants and grocery stores, a staffer will use a non-contact infrared thermometer (aka a no-touch temperature gun) to see if you are feverish — a symptom that could be a sign of infection with the coronavirus. The device, which looks like a laser gun, is pointed at your forehead and registers body temperature in a matter of a few seconds.

And increasingly, those scans are becoming the norm in airports, hospitals and workplaces around the globe, from the U.S. to India.

At the presidential debate Tuesday in Cleveland, authorities temperature-checked all attendees, according to NPR correspondent Scott Detrow, who attended the event. "There was a big sensor pointing at us, and you could see there was a video camera that put a thermal temperature bubble over everybody," he says. "The sensor picked up people's temperatures, then displayed them on two large screens."

The reason for this surge in temperature taking is clear. If people are running a fever, they're turned away at the door. Fever can be (but isn't always) a sign of COVID-19, the disease caused by the novel coronavirus.

But what can the results of a temperature scan really tell us?

Sonali Advani, an assistant professor of medicine at Duke University, distills the issue into two main questions.

The first is fundamental: Do infrared temperature guns get an accurate temperature read?

In broad terms, research points to yes.

"In general, they've shown to work reasonably well," Advani says,

Harvard Medical School physician Abraar Karan explains that studies have shown that the readings on infrared thermometers are comparable to digital thermometers. In one paper that looked at temperature scans of newborns with normal and touchless infrared thermometers, for instance, the two often had close concordance in readings.

That said, infrared thermometer guns can be a bit hard to use — and the scan results can be susceptible to outside influence.

The reason: "Infrared thermometers look at skin temperature, which can vary from core temperature," Karan says. "And skin temperature can be affected by humidity, sweat [or other weather conditions], interrupting the interface between the device and skin."

In other words, if you were to run to the gym for a pre-workout burn, your results might be affected by the sweat you pick up on the way. Plus, for infrared thermometers to capture accurate readings, they've got to be properly calibrated and used in a consistent manner, Advani says. Things can go wrong, for instance, if the temperature taker is standing too far or close to the patient. And no thermometer can account for the impact of fever-reducing medicine.

That said, Karan thinks "infrared thermometers have a net benefit." They're contactless and super-fast. That, plus the fact that they're reasonably accurate, despite the potential for false positives, makes them particularly attractive for pandemic use.

But that's only half the story, Advani says, pointing to a second, broader consideration: Namely, do such temperature readings really help minimize the chances that an undiagnosed patient will infect others? Here, medical professionals agree: Temperature screenings alone are an insufficient way to suss out and minimize COVID-19 risk.

"When we talk about temperature checks, we need to know what we are getting and what we are not getting," Karan says.

What we are getting, per Karan, is another layer of precaution. But it's certainly not foolproof, and alone, it's certainly not enough.

That's because of the nature of the virus: Roughly half of infections don't present with fever, Advani says. Plus, the virus can be contagious even in its presymptomatic phase — that is, before an infected person even shows signs of being sick. A nonfeverish yet contagious person could sail through a temperature check.

So despite the benefits of temperature checks — it can't hurt to turn away someone who's feverish — there is cause for skepticism. Infectious disease specialist Mark Kortepeter explains that infrared temperature screenings can contribute to a misguided sense of security, encouraging people to participate in activities that aren't altogether that safe.

Karan agrees.

"It can give people a sense of reassurance to have someone at the door scanning your head, which gives the illusion of safety," he says. "But it's not in any way guaranteeing your safety, and it's not guaranteeing you're not infectious."

Instead, temperature checks must just be one measure in an arsenal of risk prevention measures, our sources stress — including a thorough interview, asking people who they've been exposed to, if they're experiencing any of symptoms and where they've been traveling.

The take-home lesson: Individuals still need to take protective measures due to possible lapses in temperature screening. "Everything we do must be linked — that's the keystone of this," Advani says. "We want universal masking. And once you're in the business, you need to start looking at occupancy, ventilation, hand hygiene."

In stores, Kortepeter says it's a good idea to see what steps are being taken to minimize crowding. And at restaurants, Karan says you should consider points such as: Has indoor dining been moved outdoors, where the risk of transmission is lessened by air flow?

Finally, it's important to think about your own risk factors.

The elderly have a lower threshold for fever (while a 99-degree temperature may be within the normal range for the average individual, it may be cause for worry in an elderly person), Advani notes, so it's important for them to be more judicious than younger people.

Meanwhile, you might also wonder: Should I buy a no-touch thermometer for home use?

It's probably easier to use a digital thermometer or an infrared thermometer that goes in your ear, especially since thermometer guns may be hard for the untrained to administer properly. The one exception, Advani says, is for parents of young kids: Traditional thermometers can be challenging to use on a fidgety or sensitive kids. In these cases, the no-touch device may prove useful.

Pranav Baskar is a freelance journalist.

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