sl At least 2,000 San Francisco emergency medical workers will begin wearing rings this week that track their body temperature and other vital signs in a first-of-its-kind study to try to identify the early onset of COVID-19 and help curb its spread.

In addition to UCSF Medical Center and Zuckerberg San Francisco General Hospital staff wearing the devices, UCSF also started a campaign Monday to ask the Oura Ring’s approximately 150,000 users to share their medical data in hopes that researchers can develop an algorithm that could detect the earliest stages of coronavirus, before symptoms manifest.

It’s that early detection that would allow wearers to seek treatment, isolate themselves and, especially for doctors and nurses serving vulnerable patients, stay home from work. The team hopes to develop a COVID-19 early detection device by fall, when infectious disease experts worry coronavirus will return for a second wave.

“It will help people self-quarantine sooner, get treatment sooner,” said Dr. Ashley Mason, the UCSF assistant psychiatry professor who developed the project and is the lead investigator. “It’s expected back in the fall and we need to have tools ready.”

It’s a novel approach and one that germinated over a text chain as COVID-19 grew in California.

Two weeks ago, Mason’s study on saunas and extreme heat in the treatment of depression came to a screeching halt when UCSF froze all non-essential research.

A dejected Mason texted Harpreet Rai, the CEO of Oura Health. She had purchased the Oura Rings because they were non-invasive, wearable devices that tracked body temperature. The pair discussed COVID-19 and the CEO began wondering if the ring device that records the wearer’s vital signs could help TSA agents in airports determine whether they are going to get sick.

“I told him, ‘I have no idea how to get you into an airport, but I’d like to put them on the fingers of all UCSF’s emergency staff,’” Mason recalled.

“Let’s do it!” the CEO responded.

And just like that, in less than two weeks the pair started a collaboration that could change how medicine operates, said Benjamin Smarr, a UC San Diego assistant professor of bioengineering and data science.

“There are plenty of signs we can predict this coming,” said Smarr, who works as an Oura scientific adviser and will help crunch data. “I have no question we could do a good deal of illness prediction.”

As opposed to an occasional doctor visit that provides a snapshot of an individual’s body temperature, heart rate and other vitals, the ring collects vital health information from wearers while they are sleeping and provides aggregate data the next morning. Overnight, unbothered by the environment, the vitals will tell a story.

“Fever is one of the most reliable signs of people coming down with COVID,” said Dr. Rick Hecht, an internist and director of research at UCSF Osher Center for Integrative Medicine who is a senior researcher for the study.

One of the strategies in Wuhan, China, at the epicenter of the outbreak, was to have residents report their temperatures every day and immediately isolate anyone with a slight fever. The ring data provides a much more thorough analysis that eliminates fluctuations of temperature that can alter a thermometer reading, Hecht said.

There are data indicating that people often don’t feel sick or have a cough at the earliest onset of COVID-19, Hecht said, so that window of early detection can be key in reducing the spread.

Researchers have taken particular interest in Petri Hollmén, CEO of a Finnish firm, who tested positive for COVID-19 and had been wearing one of the rings.

On March 12, Hollmén woke up and learned his body temperature was 1 degree Celsius higher than normal — about 100.4 Fahrenheit — and his heart rate and breathing rates were slightly increased. But he felt normal, Hollmén recalled in an email to The Chronicle.

“Without a device telling me this, I would’ve just thought that I was a bit tired due to the dog waking me up twice during the night,” he said.

Alerted to that data, he called the hospital because he had been traveling for work the weekend before in an area of Austria that had since been declared a coronavirus hot spot. His test came back positive, and he has since been quarantined at home, where he still has felt few symptoms.

“Without the ring measuring my body during the night, I would not even had known about the temperature rise,” Hollmén wrote in a Facebook post. “This makes this (illness easy) to spread — you might not even recognize it.”

The short-term goal, Mason said, is for UCSF and San Francisco General emergency room doctors and nurses to get a heads-up of a fever or impending illness, not just COVID-19, so they stay home or get treated. Already taxed front-line medical workers can little afford to spread illness among themselves, she said.

The long-term goal is to collect as much data of healthy and COVID-positive patients who wore the ring and determine common bio-marker activity that precipitated symptoms, such as heightened temperature or breathing patterns. Whether they will be able to differentiate the common flu from COVID-19 is unclear.

“My hypothesis is they might look pretty similar, but that might not be the main value,” Hecht said. “It could provide an early warning sign that you have some kind of infection going on. ... The important thing with this is we’re trying to let people who might be infected know early.”

The researchers hope users will volunteer their medical information through the Oura Ring app, which has a link to the UCSF study.

“In fall, (coronavirus) will probably come back, and if we get the data now,” Smarr said, “by the time it comes we’ll have a good system testing.”

Matthias Gafni is a San Francisco Chronicle staff writer. Email: matthias.gafni@sfchronicle.com Twitter: @mgafni

Editor’s note: This story has been updated with additional information. The rings collect vital health information from wearers overnight and provide aggregate data in the morning.