Fever Scans Are Inadequate COVID-19 Screening Tools, Study Finds

From hospitals and hair salons to restaurants and resorts, establishments of all kinds have turned to fever scans as a primary COVID-19 screening method. However, new evidence shows they probably fail to detect most people who are COVID-19-positive. Instead of keeping us safe, they're serving as artificial security blankets. 

A study conducted by Natalie Lambert, PhD, an associate research professor at Indiana University School of Medicine, and Survivor Corps, the largest grassroots movement connecting COVID-19 patients and survivors, reveals a lack of connection between fever and COVID-19.

After analyzing 3,905 patients’ self-reported symptoms through an online survey, Lambert found that only 7.66% of patients exhibited a fever in the first 10 days of symptom manifestation. After accounting for the 40% of asymptomatic COVID-19 patients, she estimates the number of COVID-19 patients exhibiting fevers is only 4.6%. That means the fever scans are only detecting about 5% of people infected with SARS-CoV-2, the virus that triggers COVID-19. 

“It can be very overwhelming and nerve-wracking to learn that something that a lot of businesses and schools rely on is not effective and will not protect people," Lambert tells Verywell. "All the fever screenings before kids go to school in the morning, before you can go to your dentist or your doctor—they're not catching that many people who have COVID-19. I was very surprised when I saw the numbers myself, but it’s something everybody needs to know because people are trying to make the best decisions about how to best protect their family.”

Despite how strongly fevers are represented in COVID-19 data, Diana Berrent, the founder of Survivor Corps, says the members of the organization’s Facebook group (which included more than 110,000 people) were not remotely surprised by this revelation. 

“When we announced the results within the Facebook group, I thought it was going to be this huge splash of news—but no one was shocked,” she tells Verywell. “They were all like ‘Oh yeah, of course, that makes sense, I didn’t have a fever.’”

Hospitalized vs. Non-Hospitalized Patients 

This study highlights the fact that the majority of our data and understanding about COVID-19 is extracted from only a minority of patients.

Studies evaluating patient symptoms are usually centered on hospitalized patients, which represent only 0.19% of COVID-19 patients. This number plays an important role in our understanding of symptom manifestation, according to Lambert, because many patients may have been turned away from hospitals and told to nurse their symptoms at home, using the “Gatorade and Tylenol” recovery route.

Prior data shows that fevers occur in 83% to 99% of COVID-19 patients, while the Centers for Disease Control and Prevention (CDC) features fever at the top of its COVID-19 symptom list. This early data fueled public health policies and shaped national reopening strategies around thermal screenings—but it largely came from hospitalized patients. 

“Most of the COVID-19 patients who are hospitalized have a fever when they are admitted. However, our study shows how most of the patients were not hospitalized, and that most did not have a fever in the first 10 days,” Lambert says. “People who are recovering at home and monitoring their vitals at home don’t have anyone collecting data on them, and that's why I’ve been reaching out to Survivor Corps to try to learn about their experiences with COVID-19.”

Symptom Diversity Limits Symptom Checks

In the survey, 14.4% of patients reported feeling fatigued, which was the highest reported symptom. In order of prevalence, symptoms that followed fatigue included:

1. Cough
2. Headache
3. Shortness of breath
4. Inability to exercise
5. Altered sense of taste
6. Fever

This array of distinct symptoms poses a problem for other screening protocols, Lambert says, such as daily symptom checkers. Many universities, such as the University of Miami, employ this method—where students and employees are asked to monitor and report any daily developments. The CDC lists 11 of the most common COVID-19 symptoms on the website. The Survivor Corps survey cataloged 101. This makes patient tracking through symptom checking extremely difficult, without even factoring in asymptomatic cases. 

“There's no one or two symptoms that the majority of people have that you can use to screen people for. Even if we look at the most frequently occurring symptom—fatigue—that was only in around 14% of people,” Lambert says. “If you only track symptoms, you pretty much have to say that anyone who's feeling sick at all has to stay at home or out of school, which would shut down everything again and keep people who need medical treatment from being able to see their doctors.” 

The symptoms reported in Lambert's survey ranged from hair loss to herpes to hormone imbalances, often manifesting in ways that can’t be easily checked off in a box.  

Alternate Solutions 

The authors of this study suggest widespread rapid testing as the only efficient way to curb the spread of COVID-19. The inefficiency of fever scans and the limitations of symptom checkers make rapid tests the only real solution, Lambert says. Berrent concurs.

“We have such few tools in our tool kit in terms of stopping the spread of COVID-19, and now, based on this study we can throw the temperature and symptom checks out of the window,” Berrent says. “They are pure medical theater.” 

Widespread rapid testing curbed the spread of COVID-19 in countries like South Korea, and experts have been arguing for their use since the start of the pandemic. The U.S. has not been able to mass-produce these types of tests just yet, but many are on the market and in development, with cheap and fast saliva tests serving as key contenders.

A team at the Harvard Global Health Institute analyzed the number of people in the U.S. that would need daily rapid tests in a report for NPR. Their ideal target was a little over 14 million, which accounted for students, teachers, healthcare workers, prison inmates, and essential workers. But if the remainder of the population were to get daily tests, the demand would be much higher. Lambert says that in this case, their importance and significance trumps all other factors. 

“The policy implications for this are huge,” she says. “We need to digest this new, scary fact, and then we need to reach out to the organizational decision-makers and say, ‘Here's a new piece of scientific evidence, let's look at this and let's rework our health policies.’ We need to have those conversations regularly because with COVID-19, new information is coming out all the time, and we need to adapt and include that science in our studies.”

The information in this article is current as of the date listed, which means newer information may be available when you read this. For the most recent updates on COVID-19, visit our coronavirus news page.