A Q&A on Asymptomatic COVID-19

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TAG regularly receives questions about asymptomatic infection of COVID-19. Following are a few Q&As addressing these.

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What does it mean to have an asymptomatic case of COVID-19?

A person who is asymptomatic, is infected with COVID-19, but does not experience any of the symptoms of the infection. These persons can make up a significant number of positive cases. For example:

• A recent study from Switzerland’s University of Bern published in PLOS Medicine, found  20% of people who become infected with SARS-CoV-2 remain asymptomatic throughout infection.

• A study of residents of a nursing facility following the identification of COVID-19 in a health care worker, found that approximately 50% of the residents who tested positive were asymptomatic or presymptomatic on the day of testing. (CDC)  Pre-symptomatic people are those who are infected but asymptomatic at the time they’re tested.  These people will go on to develop symptoms later in their infection. 

• Additionally, the World Health Organization has stated “data to date suggest that 80% of infections are mild or asymptomatic.”

 

Why is this important?

Even if a person is showing no symptoms of COVID-19, they can still spread the virus. Because of this CDC recommends that anyone who has been in close contact (less than 6 feet for a total of 15 minutes over 24 hours) with someone with a documented COVID-19 infection be tested, even if they have no symptoms.​ As stated in its October 21 update, “Because of the potential for asymptomatic and pre-symptomatic transmission, it is important that contacts of individuals with SARS-CoV-2 infection be quickly identified and tested.”

 

Additionally, “Pending test results, you should self-quarantine/isolate at home and stay separated from household members.” CDC also notes that viral tests are recommended for both symptomatic and asymptomatic individuals, not only to diagnose acute infection, but also to guide contact tracing, treatment options, and isolation requirements.

 

How do I know if I have COVID-19 but am asymptomatic?

The only way to know for sure is to be tested. Testing may also be recommended for asymptomatic “healthy” people:

• Before being admitted to the hospital or procedure to protect healthcare personnel and other patients.

• Where there is significant spread of the virus in your community.

• In settings where rapid spread is more likely, such at where people are in close quarters for extended periods.

 

If I did have asymptomatic COVID-19, am I now immune?

No scientific studies have yet validated any long-term immunity to the virus by symptomatic or asymptomatic persons. According to CDC, There also is no firm evidence that the antibodies that do develop are protective; or, if they are, what levels are needed to protect against reinfection.