The idea is that thermal cameras can ferret out sick people in a crowd by finding those who have elevated temperatures, according to 11 surveillance companies NBC News found marketing the technology as a form of coronavirus detection. Fever is a symptom of COVID-19, the disease caused by the coronavirus.

But the problems with this technology, according to thermal imaging and virus surveillance experts, is that thermal imaging is an imprecise method for scanning crowds, and doesn't measure inner-body temperature.

They also noted that the coronavirus only produces a fever after a person is infected for days, if there are symptoms at all. A recent study in Iceland looking at tests from a sizable portion of the population found that 50 percent of everyone who tested positive were asymptomatic.

The rise in demand for thermal cameras also comes as governments are looking for new ways to track who is sick, including turning to smartphone location data.

On Thursday, President Donald Trump wrote in a letter to governors that the federal government plans to implement "robust surveillance testing" in an effort to help assess risks of individual counties for states struggling from businesses and school closings in response to the outbreak, though it's unclear if he was referring to thermal imaging.

A booming market

A range of companies are selling thermal cameras for fever detection. Surveillance tech startups have quickly launched new products and websites to jump on the opportunity to sell high-tech solutions to businesses desperate to get back to work. Other companies have long been in the surveillance camera market and were selling thermal imaging for years before the coronavirus swept the world.

In a video posted to Twitter, one company, Remark Holdings, pitched its fever surveillance system to the Las Vegas Police Department on Monday.

In the presentation, the company's CEO, Shing Tao, said that with their fever surveillance technology, a customer, such as a law enforcement agency, would be able to point the camera at a large crowd and "be able to identify who they are, match them with a virtual ID, capture their temperature," which, he added, his company has been testing for the past two years.

Byers Market Newsletter Get breaking news and insider analysis on the rapidly changing world of media and technology right to your inbox. This site is protected by recaptcha

Remark Holdings also makes facial recognition technology that it claims works even if the target is wearing a mask.

The Las Vegas Police Department did not respond to requests for comments.

Thermal image scanning for fever detection is broadly in use across China and South Korea, where the systems are set up in the fronts of businesses and buildings across both countries. Some U.S. businesses, like Wynn Resorts in Las Vegas and Vo's chain of grocery stores in Georgia, have set up thermal imaging systems, too, but the technology is not yet broadly adopted.

Some American companies are hoping to change that.

Companies that sell cameras for fever detection and surveillance say that demand for their products has skyrocketed. Remark Holdings' Tao said that the interest in his company's fever surveillance technology right now is "massive."

John Honovich, the founder of IPVM, a trade publication that investigates and reviews security cameras, said thermal cameras are "bar-none clearly the hottest selling item in video surveillance right now, and companies are scrambling to get products all over the place."

"The only thing I would compare it to is when I first got into the surveillance camera industry after 9/11 when price was no object," Honvovich said.

One firm, Athena Security, which sells a "fever detection system" has already clocked in more than 1,000 orders in the last two weeks since they launched their new product, the company's CEO, Lisa Falzone, said.

Some companies are combining fever-detection with face recognition and AI-powered sorting of individuals.

One company, Feevr, claims it leverages "AI face detection and thermal imaging to screen people with an elevated temp" in its marketing materials posted to its website, feevr.tech, which was only created at the beginning of the month. The company that owns feevr.tech, X.Labs, makes technology that specializes in weapons detection, which also uses thermal imaging.

"We have sold 5,000 units in the U.S., and we are building more," said Steve McClinton, a vice president of sales at X.Labs, in an email. The company wouldn't share any details about who their customers are, citing privacy concerns.

Athena Security also specialized in gunshot detection before pivoting to fever detection, which the company's CEO said is already being tested in a startup-focused co-working space called Capital Factory in Austin, which is currently closed due to a county-wide shelter-in-place order.

FLiR, a well-known security camera company that's been making thermal imaging cameras for body temperature detection cameras since 2002, said that it, too, is seeing a large demand in orders. FLiR's thermal imaging cameras for reading body temperature are approved for use by the Food and Drug Administration, unlike those from Athena Security, Feevr and Remark Holdings.