A recent paper published in the journal Travel Medicine and Infectious Disease found that temperature checks are not particularly reliable, especially among a younger demographic. The researchers evaluated 84 men in military basic training at the Swiss Armed Forces with a median age of 21 years old, each of whom had been diagnosed with COVID-19. The researchers measured their body temperatures twice a day for two weeks starting on the day that each patient was initially diagnosed. What they found was that while their fevers were initially high, their body temperatures quickly returned to normal. After five days, not one of the patients had a fever. Further, 83 percent of the patients evaluated never even developed a fever and, with one exception, none of them suffered from a fever for longer than three days. The researchers point out that those with the coronavirus are known to be contagious for “up to 10 days post-infection,” which means that these individuals with COVID-19 can still spread the contagion even though their body temperature is normal.ae0fcc31ae342fd3a1346ebb1f342fcb “Screening for fever is not sensitive enough to detect the vast majority of COVID-19 cases in the age group between 18-25 years,” the researchers concluded. “Even a low-temperature cut-off value of 37.1°C [98.8 degrees Fahrenheit] will miss more than a third of symptomatic cases of COVID-19 on the day of diagnosis and will cause a large number of false-positives.” Beginning in June, coronavirus began to strike a younger demographic, with nearly half of new coronavirus cases in some states spread by people between the ages of 18 and 35. As a result, which symptoms were considered “common” started changing, too. And that includes fewer and fewer having a fever. “Younger people often do come in now—somewhat to our surprise—without fever,” William Schaffner, MD, an infectious disease professor at Vanderbilt University, told WGN9 in July. RELATED: For more up-to-date information, sign up for our daily newsletter. All of this means that if young people with COVID-19 were given temperature checks outside of a store, their office, or a travel border, they wouldn’t raise any red flags, even though they could still have the virus and infect others. The researchers particularly want those handling border control measures to be aware of the ineffectiveness of temperature checks, and recommend they switch gears. “We advocate the evaluation of, novel non-invasive screening approaches, such as testing saliva samples for SARS-CoV-2 with rapid follow-up on positives,” the researchers note. “This may prove to be a fast and more sensitive alternative to body temperature screening at borders.” And for more on COVID safety measures that aren’t working, check out Only These 6 States Can Currently Contain COVID, New Research Shows.