Marine study suggests widespread testing key to slowing transmission of asymptomatic cases


A new study of about 2,000 Marine recruits suggests that regular, widespread testing is key to slowing down the spread of the coronavirus.

Researchers at Mount Sinai collaborated with a U.S. Navy program that quarantined Marine recruits before sending them to training camp.

Among the recruits, 51 were found to be infected with the virus and only five had experienced any symptoms, which were very mild.

“In this age group it’s rare for them to have symptoms and none of them get particularly sick,” said Dr. Stuart Sealfon, professor of neurology at the Icahn School of Medicine at Mount Sinai and one of the lead authors of the study, which was published this week in the New England Journal of Medicine. “They were completely surprised when they found out they were infected because they felt perfect.”

The recruits were told to quarantine at home for two weeks before they came to another facility where they were under a strict quarantine with infection control measures for an additional two weeks. During that time, they were tested for the virus before they could go to a training camp.

The recruits were also subject to regular health screenings and symptom and temperature checks.

“From the daily temperature checking and from the daily symptoms screening, it turned out that no cases were identified. All of the cases were identified by testing independent of symptoms,” said Dr. Sealfon.

While some essential workers are required to get regular testing through their employers, that is not the case for most Americans, who only get tested for the virus if they know they have been exposed or feel sick.

The results of this study suggest that under that model, many asymptomatic cases are being overlooked.

“Among these asymptomatic Marines, some of them had absolutely extraordinary levels of virus… we couldn’t show any of them were super spreaders, but this is what one would expect an asymptomatic super spreader would look like,” said Dr. Sealfon.

That is why he is calling for testing to be scaled up considerably.

“It’s the only way we’re going to get this pandemic under control,” he said. “We don’t have enough testing to do this countrywide in everybody a couple times a week, but we can do much more testing than we’re doing.”

Dr. Sealfon says pooling samples together can help to considerably scale up testing.

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