Experts Think People Without Symptoms May Be Driving the Spread of Coronavirus

Photo credit: BSIP - Getty Images
Photo credit: BSIP - Getty Images

From Prevention

As cases of the novel coronavirus continue to grow around the world, fears are mounting. COVID-19, the respiratory illness caused by the virus, has sickened hundreds of thousands of people globally, according to the World Health Organization (WHO).

People with COVID-19 have shown “a range of symptoms,” according to the WHO, but they tend to be similar to the flu, which includes fever, dry cough, fatigue, sore throat, aches and pains, and headaches. In more advanced cases, people are experiencing shortness of breath. COVID-19 can also lead to complications like pneumonia and bronchitis, according to the Centers for Disease Control and Prevention (CDC).

Currently, the CDC says “people are thought to be most contagious when they are most symptomatic,” or when the feel the sickest. “Some spread might be possible before people show symptoms.”

But as new studies emerge, experts are starting to wonder whether people with mild symptoms—or no obvious symptoms at all—are actually driving the spread of COVID-19. It is now believed to be “a highly-infectious organism,” says Rajeev Fernando, M.D., an infectious disease expert in Southampton, New York. Here’s what experts know about how COVID-19 incubates and spreads so far, plus what you should do to stay safe.

First, a quick primer on how coronavirus spreads.

Coronaviruses usually spread from an infected person to others via respiratory droplets that are released into the air when they cough or sneeze, according to the CDC. Those droplets are then breathed in by others, infecting them in the process. Coronavirus can also be spread through close contact, such as touching or shaking hands.

You could also pick up the virus by touching a contaminated surface and then touching your mouth, nose, or eyes before you wash your hands. While this is “not thought to be the main way the virus spreads,” per the CDC, experts say it is certainly a possibility.

Dr. Fernando points to new research in The New England Journal of Medicine, which found that the novel coronavirus can survive up to three hours in the air, up to four hours on copper, up to 24 hours on cardboard, and up to two to three days on plastic and stainless steel.

What is the incubation period for the novel coronavirus?

It seems to be between two and 14 days. That means someone can be infected with the virus for up to two weeks before they begin to show symptoms. On average, though, it seems like most people have an incubation period of 10 days, says William Schaffner, M.D., an infectious disease specialist and professor at the Vanderbilt University School of Medicine.

So, can people spread COVID-19 before they show any symptoms?

This novel coronavirus, officially named SARS-CoV2, was only recently found to infect people, and there’s a lot we still don’t know about it, says infectious disease expert Amesh A. Adalja, M.D., senior scholar at the Johns Hopkins Center for Health Security. However, new research is pointing to the potential impact of asymptomatic spread.

For instance, a case report published in the New England Journal of Medicine detailed how a woman from Shanghai traveled to Germany for a business trip between January 19 and January 22. She had no symptoms of coronavirus during this time and only became sick on her flight back to China. She was diagnosed with COVID-19 on January 26.

But on January 24, a businessman who met with the woman on January 20 and 21 developed symptoms of coronavirus. He went back to work on January 27 and later tested positive for COVID-19. “We discovered that shedding of potentially infectious virus may occur in persons who have no fever and no signs or only minor signs of infection,” the report’s authors concluded.

This definitely implies that people can spread COVID-19 before they have symptoms, which is unusual. “We’ve never seen that with a coronavirus before,” Dr. Adalja says.

In a study posted to medRxiv, which has not yet been peer-reviewed, researchers concluded that 48% of infections studied in Singapore were likely transmitted by people who didn’t feel sick or who were not yet diagnosed with an infection. In China’s Tianjin province, they believe 62% of the cases analyzed resulted from people who were carrying the virus without obvious symptoms.

New research published in the journal Science also found that a majority of cases in China were transmitted by “undocumented infections” in the period before the country placed travel restrictions on Hubei province on January 23. “This high proportion of undocumented infections, many of whom were likely not severely symptomatic, appears to have facilitated the rapid spread of the virus throughout China,” the authors wrote.

Dr. Fernando says he believes “the spread is asymptomatic, especially in youngsters who actually get infected. They can then infect others. That’s a really big concern. This is an infectious disease pandemic that comes once in a century and blows everything out of the water. It’s just unbelievable, the numbers.”

That’s why following preventive measures is so important right now.

The CDC says that the best way to lower your odds of contracting COVID-19 is to avoid being exposed to the virus, as there is currently no vaccine. In fact, these new studies highlight just how important it is to follow social distancing and hand hygiene recommendations as coronavirus continues to spread throughout the U.S.

The following preventive actions can help protect yourself and those around you:

  • Avoid touching your eyes, mouth, or nose.

  • Avoid close contact with anyone who appears to be sick.

  • Wash your hands well and frequently with soap and water for at least 20 seconds.

  • Use alcohol-based hand sanitizer when soap and water isn’t readily available.

  • Clean and disinfect frequently touched objects and surfaces.

  • Stay home if you develop cold or flu-like symptoms.

  • Follow social distancing recommendations and maintain a six-foot distance from other people.

  • Avoid nonessential travel to areas with active COVID-19 outbreaks.

  • Visit the website for your local health department to make sure you are getting accurate updates.

If health officials are urging you to stay home as much as possible, it’s extremely important to do so. In light of this new research, it’s possible that you could be carrying the virus, feel totally healthy, and unknowingly spreading it to others (including those in high-risk groups, like the elderly).

Ultimately, there’s still a lot researchers are trying to learn about this virus—but we all need to play a part in preventing the spread. “We don’t have all the pieces of the puzzle yet, but we’re working on it,” Dr. Schaffner says.


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