Skip to main content

Health Library

Up to 45% of people with COVID-19 may be asymptomatic

A woman in a face mask walks out her front door.

June 30, 2020—How important are masks and social distancing in slowing the spread of COVID-19? Consider this: A recent study found that as many as 45% of people infected with the virus have no symptoms.

The study was published in the Annals of Internal Medicine. It looked at information from 16 different testing studies from around the world. The data came from prisons, cruise ships and nursing homes, as well as thousands of volunteers from cities like Reykjavik and San Francisco. People were tested and checked for symptoms. Approximately 40% to 45% of those who tested positive had no symptoms.

The study also found that people with no symptoms could transmit the virus for a long time, possibly longer than two weeks.

The study's findings highlight the importance of staying 6 feet away from people in public and wearing a cloth face mask. Masks help slow the spread and can prevent you from unknowingly spreading the virus to others.

Stopping the spread: A review

According to the Centers for Disease Control and Prevention, here's how you can best protect yourself and others from COVID-19:

  • Wash your hands often. Soap and water are best. Be sure to lather for 20 seconds. If you're not near a sink, a hand sanitizer that contains at least 60% alcohol will do in a pinch.
  • Avoid touching your eyes, nose and mouth with unwashed hands.
  • Avoid close contact with people who are sick.
  • Stay at least 6 feet away from other people. That's about 2 arms' length.
  • Wear a cloth face mask when out in public.
  • Clean and disinfect frequently touched surfaces daily.
  • Be on the alert for symptoms. These can include fever, cough and shortness of breath.

Learn more about COVID-19 by visiting our Coronavirus health topic center.

Read more breaking news Related stories

Sign up for our health e-newsletter