In the race to control the coronavirus, some public health experts have great expectations for a humble tool: a “smart” thermometer that is feeding data about surging fevers into a new online “Health Weather” map of the United States. Especially while diagnostic tests remain scarce, the device may provide early warnings for officials chasing down local outbreaks before the disease can spread.

Kinsa, a San Francisco-based start-up, began selling and donating its smart thermometers eight years before the onset of covid-19. Today, more than 1 million U.S. consumers are able to use them to link to a mobile phone app that relays data about fevers and other symptoms to its corporate headquarters, says Inder Singh, the firm’s founder and chief executive.

Kinsa already has used its data to forecast the spread of seasonal influenza — accurately, and about two weeks ahead of the Centers for Disease Control and Prevention projections, Singh says. Now he says he hopes the thermometer can alert public health officials to new outbreaks of the coronavirus.

“The thermometer is the first and only device you use in the home when illness strikes,” Singh says. “We’ve turned it into a communications system. I can’t tell you for sure right away if it’s covid-19, but it immediately tells us, ‘Look here! Something important is going on!’ ” Subsequently, he says, the system can help triage users to the care they require, while also capturing signs of spreading illness so that authorities can step in when needed.

As of last week, Kinsa’s online map allows users to scroll over counties throughout the United States to monitor both the flu and unexpected, or “atypical” fevers that might indicate covid-19.

“You’re desperate for hope at a time like this, and this gives me hope,” says Benjamin Dalziel, an Oregon State University scientist who collaborates on research funded by Kinsa.

The company’s name derives from “kin,” signifying its emphasis on family, Singh says. The app encourages owners to use it by offering instant, personalized medical advice, such as when to take fever-reducing medicine. It can even connect users with a doctor, through its partnership with the telehealth company Teladoc.

For the sake of harried parents caring for children in the middle of the night, the app also features a distracting video game kids can play while their temperatures are being taken.

“The real benefit is to get that data in real time,” says Jennifer Radin, an epidemiologist with the Digital Medicine Division at Scripps Research Translational Institute. Traditionally, such information is unavailable for one to three weeks, during which doctors and hospitals relay reports to the CDC, says Radin, adding: “That way, we lose valuable time to respond.”

Kinsa’s thermometer is one of several high-tech tools that may be deployed in coming years to detect new diseases, in an emerging field known as digital epidemiology. Experts hold similar hopes for wearable devices such as a Fitbit, which tracks changes in resting heart rates and activity levels — potentially clues to illness.

On Wednesday, Radin urged any Americans over 18 who use activity trackers such as Fitbits and smartwatches to collaborate with her research team by sharing their health data on the mobile app MyDataHelps. The devices can send alerts about physiological changes, after which users can record other symptoms. “We’re hoping it will help pick up outbreaks of covid-19,” she said.

Radin was the lead author of a recent study in the Lancet on the potentially “vital” role of Fitbits in disease detection, based on analyzed data from 47,249 people in five states.

The thermometers, Fitbits and smartwatches belong to the “Internet of things” — connected devices including cars that can summon help after a crash, thermostats that report home temperatures to your local utility, and Alexa, the Amazon speaker that may soon try to sell you cold medicine if it hears you cough.

Singh, a former executive officer of the Clinton Foundation’s Clinton Health Access Initiative, says he founded his company after realizing that “no matter what we would do there would always be a ceiling in curbing infectious illness spread unless we knew where and when it was starting.” He now hopes that U.S. government agencies such as the CDC will recognize Kinsa’s public health mission and collaborate, sharing data and providing financial support so that it can scale up.

This hasn’t happened to date, however, and a CDC spokesman declined to answer questions about Kinsa’s project, other than to say that while it was not working directly with the firm, the agency “appreciates the efforts of so many companies working across the private sector to address this new threat.”

Kinsa has raised $37 million from venture capitalists, Singh says. It earns revenue from not only thermometer sales but also licensing data through Kinsa Insights to businesses selling health-related products. Clients, including Clorox, according to an online case study, use the information to manage inventory, such as making sure stores are carrying extra disinfectant products during local fever spikes.

They can also “maximize marketing returns by reaching high-intent consumers when they most need your product,” according to the site. Yet Singh says the data is never individualized, but aggregated while provided on a county-by-county basis, complying with HIPAA confidentiality laws. What that means is that Clorox might target an ad to consumers sharing a Zip code in an area where fevers have been breaking out.

About three years ago, Kinsa began working with low-income schools, giving away its thermometers to students’ families. Its “FLUency” program now involves about 1,400 schools throughout the country, Singh says.

“We were seeing a flood of kids every day lining up at my office because their parents couldn’t afford thermometers,” recalled Alisha Palmer, a nurse for Jackson Park Elementary in Kannapolis, N.C., one of the first schools to join the program.

Most of the parents held low-wage jobs at local restaurants, retail shops or the chicken processing plant. Few if any of them could afford to stay home from work unnecessarily, so instead they counted on the school to let them know if and when their children were ill.

“I was having these kids pour off the bus after 30 minutes to an hour of being crowded together,” Palmer says. “That of course led to many more children getting sick. We’re a small school, less than 500 students, but at one point I was seeing 50 kids a day.”

Now, however, parents are able to measure children’s temperatures at home and also see information on their phones about the severity of illnesses going around. Palmer says her daily caseload has dropped by 50 percent, and parents are grateful for the steady stream of information about students’ health — particularly now.

The pandemic has sharply increased demand for Kinsa’s thermometers while also raising prices for components manufactured overseas, Singh said. U.S. sales orders recently reached 10,000 per day, with at least a two-week backlog on delivery, he adds. The price has also shot up, rising from $20 to $35.99 when ordered from the company’s site. The Amazon listing said: “We don’t know when or if this item will be back in stock.”