This Is Who Is Transmitting 80 Percent of Coronavirus Cases, Study Says

A new study shows how a majority of COVID-19 cases are likely spreading in your community.

Since the coronavirus first came about, scientists and medical experts have been researching how the pandemic is transmitted and who is most at risk. The main focus has been on infected patients who show common symptoms—including fever, cough, and loss of taste and smell—which has resulted in global safety measures, such as self-quarantining, social distancing, and wearing face masks. However, research now indicates that another, much larger group is far more dangerous than those we know are infected: asymptomatic people. In fact, according to a new study, 80 percent of coronavirus cases are asymptomatic.

A May study, which was published in Thorax, looked at a cruise ship that carried 217 passengers and crew members to determine how COVID-19 spreads. The research found that of the 128 people who tested positive, 104 (or about 81 percent) did not exhibit any symptoms.

That number is a huge jump from what has been reported so far. The Centers for Disease Control and Prevention (CDC), for instance, estimates that only 35 percent of infections are asymptomatic. This means that asymptomatic transmission may be a greater threat than experts had originally predicted, especially in confined spaces, such as households, offices, hospitals, nursing homes, and prisons.

"A lot of this is thought to be settled science, but I think that there are still a lot of questions we have about when asymptomatic transmission occurs and the circumstances that it occurs in," Amesh Adalja, an infectious disease expert and senior scholar at the Johns Hopkins University Center for Health Security, told Business Insider.

man in suit holding newspaper and coffee and wearing a face mask in city

Another May study involved testing 78 infected patients in Wuhan, China, and found that 33 of them (or 42 percent) were asymptomatic. Researchers also discovered that asymptomatic individuals skewed younger—between the ages of 26 and 45—and female (nearly 67 percent were women). The good news? The asymptomatic people were contagious for only three to 12 days, compared to 16 to 24 days among the patients who showed symptoms.

But just because these so-called "silent spreaders" aren't contagious for as long, doesn't mean they're harmless. In a statement published in The New England Journal of Medicine, researchers at the University of California, San Francisco said, "asymptomatic transmission of [COVID-19] is the Achilles' heel" of America's current public health strategy surrounding symptom-based screenings.

This confirms the importance of population-wide testing—particularly as states start to reopen—in order to find out exactly how many people may be unknowingly spreading coronavirus and where outbreaks may be lurking undetected. It also emphasizes how essential it is to wear face masks and practice social distancing, even if you don't feel sick. And for more information about asymptomatic individuals, check out This Is Why Some People Have Coronavirus Symptoms and Others Don't.

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