Fever, symptom screening misses many coronavirus cases

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FILE - In this May 27, 2020 file photo, Marine recruits line up at Parris Island Recruit Depot, S.C. A study published on Wednesday, Nov. 11, 2020 found that despite temperature and COVID-19 symptom checks and strict quarantines before they were allowed to start training, new Marine recruits spread the virus to others even though hardly any of them had symptoms. None of the infections that occurred were caught through symptom screening. (AP Photo/Lolita Baldor)

Temperature and COVID-19 symptom checks like the ones used at schools and doctor's offices have again proved inadequate for spotting coronavirus infections and preventing outbreaks.

A study of Marine recruits found that despite these measures and strict quarantines before they started training, the recruits spread the virus to others even though hardly any of them had symptoms. None of the infections were caught through symptom screening.

The study, published Wednesday in the New England Journal of Medicine, has implications for colleges, prisons, meatpacking plants and other places that rely on this sort of screening to detect infections and prevent outbreaks.

“We spent a lot of time putting measures like that in place and they’re probably not worth the time as we had hoped,” said Jodie Guest, a public health researcher at Atlanta's Emory University who had no role in the research.

“Routine testing seems to be better in this age group” because younger adults often have no symptoms, she said.

The study was led by researchers from the Icahn School of Medicine at Mount Sinai in New York and the Naval Medical Research Center.

It involved 1,848 Marine recruits, about 90% of them men, who were told to isolate themselves for two weeks at home, then in a supervised military quarantine at a closed college campus, The Citadel in Charleston, South Carolina, for two more weeks. That included having a single roommate, wearing masks, keeping at least 6 feet apart and doing most training outdoors. They also had daily fever and symptom checks.

The recruits were tested for coronavirus when they arrived for the military quarantine and 7 and 14 days afterward. Sixteen, or about 1%, tested positive on arrival and only one had any symptoms. Another 35 -- an additional 2% -- tested positive during the two-week military quarantine and only four had symptoms.