People in most of the United States are currently staying at home to slow the spread of COVID-19, the disease caused by the novel coronavirus. While we stay isolated and practice social distancing, many folks are thinking ahead to what society might look like after restrictions are eased, and which safety measures will help keep people safe.

One strategy that continues to pop up is temperature checks for fever — a tactic being used in Wuhan, China, as the city where the virus began attempts to resume everyday life. The process is happening in the U.S. too: Amazon announced it would use thermal cameras to check employees’ temperature, and some grocery store workers are undergoing checks before reporting to their jobs.

Once infections in the U.S. begin to decline, we might start seeing these measures on a larger scale. Colorado Gov. Jared Polis (D) recently announced a “slow roll” toward reopening, which included temperature checks at the workplace. California remains under a stay-at-home order, but Gov. Gavin Newsom (D) described possible temperature checks at restaurants as part of his state’s eventual reopening strategy. Disney parks are also considering temperature checks on guests once lockdown restrictions are lifted.

But are temperature checks really the best way to monitor and control the spread of coronavirus?

According to some infectious disease experts, the method has a lot of flaws and shouldn’t be the only measure to address the pandemic once activity resumes.

Large-scale temperature checks may not show everyone with COVID-19

According to the Centers for Disease Control and Prevention, COVID-19 symptoms can develop anywhere between two and 14 days after exposure — meaning someone can have the virus and not know it.

“The incubation period ... is variable between patients,” said Jai Marathe, an infectious disease physician at Boston Medical Center and assistant professor at Boston University School of Medicine. “During this time, the virus is multiplying. Once it reaches a critical level, it causes the body to respond with robust symptoms. The duration for this to happen is variable in different patients, and in the case of COVID-19, one of the most common symptoms experienced by patients is fever.”

While fever can be expected in many cases, experts have also learned that there’s no guarantee it’ll be present for everyone. COVID-19 doesn’t produce the same symptoms in each patient (and a large portion of cases might be asymptomatic). One study published in the Journal of the American Medical Association, which analyzed 5,700 people seriously ill with COVID-19 in the New York City area, found that two-thirds did not have a fever.

“While fever is one of the more common manifestations of SARS-CoV-2 infection, it is not universal,” said Stephen P. Juraschek, a physician at Beth Israel Deaconess Medical Center and assistant professor of medicine at Harvard Medical School. “Unfortunately, we are unable to predict whether or not someone will be symptomatic and what their symptoms will be.”

It’s unclear how many people infected with the coronavirus are asymptomatic “silent spreaders,” but scientists estimate the number is considerable.

“The body’s immune response plays a big role in the severity of infection,” Marathe said. “The immune defense in certain individuals is able to protect the patient from manifesting any symptoms, which is what we refer to as ‘asymptomatic.’ The immune response is also influenced by other factors like age [and] underlying medical conditions.”

For this reason, Juraschek noted that temperature checks might not always be effective.

“Asymptomatic, mild, or delayed cases can be missed,” he said. “So, while better than nothing, such approaches do not replace other critical interventions like hand washing, 6-feet distancing, using a mask or covering one’s mouth when coughing.”

Natasha Chida, assistant director of the infectious diseases fellowship program and assistant professor of medicine at Johns Hopkins, also pointed out the shortcomings of temperature checks.

“It can’t necessarily hurt to implement temperature checks in public places to limit people who are symptomatic from infecting others,” Chida said. ”But I think you will end up missing people who are infected and are either not yet manifesting symptoms — or who are not going to manifest symptoms.”

Temperature checks might be challenging for businesses

In addition to the personal protective equipment that would be required to implement large-scale temperature checks — much of which is difficult to acquire right now — businesses might face logistical hurdles.

“Many of us do not have thermometers at home and currently you cannot buy one easily in the market,” Marathe said.

“The logistics of when and for whom you do the temperature check do not seem to be well thought out,” Marathe continued. “For example, how frequently do you check? What about the employees who take medications like Tylenol for headaches or arthritis, in whom a fever may be suppressed?”

Chida also has questions:

“Who is going to be measuring the temperatures? Are people going to be measuring their own temperatures? If you’re using oral thermometers, you’re going to need many of them. If you’re using ear or forehead scanners, those can be unreliable if you don’t use them correctly. It might depend on the size of the business in terms of how practical it is.”

Other safety measures could be effective

The experts noted that temperature checks shouldn’t be the singular method of monitoring and preventing the spread of coronavirus. And for now, staying apart might still be our best tool.

“If things are going to open back up, we’ll still need to keep up social distancing until we have better measures of aggressive contact tracing and more therapeutics available,” Chida said. “If people are going to be in a public space, they should still be keeping 6 feet apart.”

Juraschek said widespread testing for infection and contact tracing will also be essential.

“Testing is a critical tool for case tracking, isolating positive cases and estimating disease burden in the community,” Juraschek said. “In many ways, it can help predict where we are in the pandemic, in terms of rate of infection spread and herd immunity.”

But virus screening isn’t infallible, Juraschek pointed out, because someone who is negative today could become positive tomorrow.

Antibody testing, or being able to detect if someone has already been infected with COVID-19, is useful, too, but it’s not a perfect solution, either. The duration of when someone who has recovered from the coronavirus would test positive for antibodies varies from person to person, and sometimes you can get a false negative, Marathe said.

Further, Marathe explained, “we do not have adequate information on whether the presence of an antibody means that the individual has protection against the virus.”

Ultimately, some of the best practices for limiting the spread of infection are within our control. That includes staying home if you feel ill, practicing proper hand-washing, covering a cough and wearing a mask in public places.

“Some form of screening will likely result in more timely capture of symptomatic [people] and at the very least make employees more aware and more likely to self-monitor before reporting for work,” Juraschek said. “However, as previously mentioned, these approaches are not foolproof and other standard hygienic and public precautions should be applied.”