COVID-19 still has a lot of unknowns—but here's what we know about how the virus is transmitted.

By Jessica Migala
Updated August 18, 2020
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With nearly 5.5 million confirmed cases of coronavirus in the US (and close to 22 million cases worldwide), it's clear that neither COVID-19, nor the anxiety surrounding it, is going anywhere soon.

Because the virus (technically SARS-CoV-2, FYI) that causes this illness is new, lots of the fear surrounding COVID-19 stems from how little we know about it. Luckily, experts do know some pretty important things about the virus' transmission, or how the coronavirus does—and doesn't—spread.

In general, how does the coronavirus spread?

According to the Centers for Disease Control and Prevention, COVID-19 is spread mainly from person-to-person, usually via close contact (within six feet). Simply being near an infected person who coughs, sneezes, or talks can expose you to their infected respiratory droplets, the CDC says. It those virus-containing particles land in your eyes, nose, or mouth, or if you inhale them into your lungs, you could become infected. Some people may be capable of spreading it to others even though they don't have any symptoms, the CDC points out.

You might also acquire the infection if viral particles get on your hands by, say, touching contaminated surfaces or shaking hands with someone whose hands are contaminated with the virus, and then touching your eyes, nose, or mouth. "A sneezing or coughing person will cover their mouth, get it all over their hand, and then touch something that you then touch," Robert Murphy, MD, an infectious disease expert at Northwestern University, tells Health. The virus can then gain entry into your body when you touch your own face, he adds.

One other note: While the virus has been detected in stool, it's still not clear whether it can be acquired through fecal-oral transmission, according to a review posted online March 12 by Clinical Gastroenterology and Hepatology.

Can you tell if someone is sick with coronavirus?

Unfortunately, the only way to truly know if someone has COVID-19 is to test them—that's because the symptoms of the illness may look extremely similar to that of the common cold or flu: cough, fever, body aches.

It's also important to know that not everyone who is infected with coronavirus shows symptoms—as is the case with asymptomatic carriers. They can harbor the virus and spread it to other people before developing symptoms. It's also possible for their symptoms to be so mild that they're not aware they have the virus. The CDC estimates that 50% of transmission occurs prior to symptom onset.

How long does coronavirus stay on surfaces?

The recent coronavirus outbreak sparked a review published in February in the Journal of Hospital Infection, which looked at other coronaviruses (including SARS, MERS, and other endemic human coronaviruses), and determined that they can live on surfaces like metal, glass, or plastic for anywhere from two hours to nine days. Subsequent research in the New England Journal of Medicine found that the virus can live on copper for up to four hours, on cardboard for up to 24 hours, and on plastic and stainless steel for two to three days.

However, investigators examining outbreaks of COVID-19 on three cruise ship voyages in February and March reported the first evidence that the virus may hang around much longer than than initially thought. Traces of the virus were found in the cabins of infected Diamond Princess passengers (including symptomatic and asymptomatic individuals) 17 days after their cabins were vacated, according to the March 23 Morbidity and Mortality Weekly Report from the CDC. However, the authors of the report say the data cannot be used to determine whether the virus from transmitted from person to person through contaminated surfaces.

Even if we don't know exactly how long the virus lingers on surfaces, we do know that disinfecting surfaces is considered "best practice" for helping to prevent transmission of the virus. So again, wiping down common surfaces (and avoiding touching common surfaces if possible) will help decrease the spread. The CDC recommends cleaning tables, countertops, light switches, doorknobs, and cabinet handles regularly. However, it’s unlikely that COVID-19 is spread by mail or packages; if it were, there’d be even more cases, says Dr. Murphy.

Does coronavirus spread through food?

It's a fair question—especially since lots of other viruses, like norovirus or other gastrointestinal viruses, can spread via contaminated food. But, while a risk can't be ruled out if an infected person prepares the food, or you buy it from a highly trafficked buffet, the coronavirus doesn't appear to be spread by food, per The New York Times.

Thomas File Jr., MD, chair of the infectious disease division at Northeast Ohio Medical University, and president of the Infectious Diseases Society of America, addressed the topic in a recent media briefing. "I don’t think we're so concerned about produce, although anything that’s being touched by hands, where people could be having the virus on their hands, could potentially be at risk." He recommended that people wash their produce.

What exactly is "community spread," and how is that related to coronavirus?

The term "community spread" entered the nation's coronavirus vocabulary as outbreaks of disease popped up across the US, initially in densely populated metropolitan areas. According to the CDC, community spread means people in a specific area have been infected, even if they don't how or where they acquired the illness. In other words, they didn't have to know someone with COVID-19 or have a recent history of travel to a place where an outbreak has occurred to become infected.

New York City, once a major epicenter of the disease, experienced rampant community spread early in the pandemic. Today, there are 33 "hot spot" states where the number of COVID-19 cases is on the rise and positivity rates (the percentage of coronavirus tests that come back positive) are rising or persistently high, according to the Henry J. Kaiser Family Foundation.

It only solidifies the need for people to follow the CDC's preventive measures: avoid close contact with other people, especially people who are sick; wear a cloth face covering, especially when social distancing isn't possible; try not to touch your eyes, nose, and mouth; frequently disinfect objects that are touched regularly; and wash your hands often with soap and water.

The information in this story is accurate as of press time. However, as the situation surrounding COVID-19 continues to evolve, it's possible that some data have changed since publication. While Health is trying to keep our stories as up-to-date as possible, we also encourage readers to stay informed on news and recommendations for their own communities by using the CDC, WHO, and their local public health department as resources.

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