According to a new federal government-backed study, widespread Covid-19 testing has helped stop the asymptomatic spread among nearly 2,000 Marine recruits, providing more evidence that frequent testing can help contain the virus.
Dr. Stuart Sealfon, the paper's senior author and neurologist at the Icahn School of Medicine at Mt. Sinai in New York City, said the study shows public health measures need to be complemented with comprehensive testing to combat the coronavirus.
"You need to implement all of these infection control measures as best you can and complement or integrate them with as many tests and as frequent tests as possible," he said in a telephone interview. He added that "you cannot rely on testing alone either".
Many epidemiologists and public health professionals have repeatedly urged the Trump administration to increase the availability of tests across the country. While the tests have increased, Adm. Brett Giroir, the Trump administration's deputy secretary of health and tsar for virus testing, said there is no need to test people who are not experiencing symptoms.
The new study, released on Wednesday, shows the importance of frequent testing as an adjunct to infection prevention measures, Sealfon said.
Funded by the Defense Health Agency, the Naval Medical Research Center, and the Defense Advanced Research Projects Agency, the study examined 1,848 Marine recruits in basic training on Parris Island, South Carolina from May 12 to July 15. The average age of the participants was 19 years. the study says.
Before entering basic training, recruits were asked to be quarantined at home for two weeks and then placed in supervised two-week quarantine on a college campus, the study says. Before entering Parris Island, every recruit had to present a negative Covid-19 molecular test. Upon entry, recruits were also asked to adhere to public health guidelines, including wearing masks and social distancing.
To study the asymptomatic spread of the virus in the relatively young population, the researchers tested all participants using a nasal swab molecular test within two days, seven days and 14 days of their arrival on Pettis Island.
The study found that 16 of the recruits tested positive for Covid-19 upon enrollment within two days of their arrival, despite having previously been quarantined for four weeks. Another 24 tested positive seven days after arriving at the base, and 11 more recruits tested positive on day 14. Only five participants reported symptoms of Covid-19.
Another 26 recruits who did not participate in the study tested positive for the virus on day 14, the study says.
Harm van Bakel, a geneticist at Mt. The Sinai Icahn School of Medicine performed genetic sequencing of the virus to better understand how it spread through the population. He found that despite all of the public health protocols implemented by the Marine Corps, there were six separate infection clusters on the base.
"If you don't do frequent and comprehensive testing in this type of cohort of young adults, it's very difficult to find all positive cases," he said. "So if you just rely on symptom screening, social distancing, and guidelines on how to wear masks, it is still possible to miss cases."
Sealfon, the senior writer, said their results are in line with those of the National Basketball Association when they tried to create a so-called bubble that allowed them to end their season. The NBA ran daily Covid tests of all players and staff in the bladder and successfully kept the virus at bay.
Sealfon added that colleges and universities would do well to take note of the results of their study. While the infection control protocol has been strictly followed at the naval base, college students practice less social distancing and wearing masks, which makes frequent testing all the more important.
"The public health measures are very important, but they are not enough," he said. "This is a tough virus. You can't disappoint your guard."