What Is Asymptomatic COVID-19? - Healthline

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What to Know About Asymptomatic COVID-19

Medically reviewed by Elizabeth Thottacherry, MD — Written by Daniel Yetman on March 30, 2022

Definition
Asymptomatic vs. pre-symptomatic
Prevalence
Transmission
When to get tested
Recommendations
Bottom line

Developing COVID-19 affects everybody differently. Some people don’t experience any symptoms, while other people have severe symptoms that require hospitalization. If no symptoms appear, it’s known as asymptomatic COVID-19.

The coronavirus that causes COVID-19 can still be transmitted to others even if you’re asymptomatic. That’s why it’s important to follow proper self-isolation protocols if you test positive for COVID-19 but don’t have symptoms.

Read on to learn more about asymptomatic COVID-19, including how common it is and what you should do if you test positive but don’t have symptoms.

What does asymptomatic COVID-19 mean?

Asymptomatic COVID-19 is when you contract the coronavirus, SARS-CoV-2, but don’t develop any signs or symptoms that are commonly associated with the COVID-19 infection. With asymptomatic COVID-19, you can still transmit the coronavirus to other people.

When symptoms do appear, they usually appear 2 to 14 days after exposure to the virus and most commonly include:

fever
chills
fatigue
headache
cough
sore throat
loss of taste and smell
congestion or runny nose
diarrhea
nausea or vomiting
shortness of breath or difficulty breathing

According to the Centers for Disease Control and Prevention (CDC), the Omicron variant causes similar symptoms as other variants, but it transmits more easily between people.

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What’s the difference between asymptomatic and pre-symptomatic COVID-19?

Asymptomatic and pre-symptomatic COVID-19 both refer to people who don’t have any signs or symptoms of COVID-19. But there is a difference between these two terms.

Asymptomatic means that you’ve tested positive for COVID-19, but have not developed symptoms, even after the incubation period for the coronavirus has passed. The incubation period is the time it takes between when you’re exposed to the virus and when your symptoms appear.
Pre-symptomatic means that you’ve tested positive for COVID-19, but haven’t developed any symptoms yet. It takes around 2 to 14 days to develop symptoms, with the typical incubation period being around 4 to 5 days.

How common is asymptomatic COVID-19?

Estimates on the occurrence of asymptomatic COVID-19 vary between studies. The differences are based on how the studies were designed and the population that was examined.

In a 2021 research review, experts found that the prevalence of asymptomatic COVID-19 among people with a confirmed COVID-19 infection was 40.5 percent.

The experts found that studies in Asia reported the lowest percentage of asymptomatic people, possibly due to the city-wide screening programs in China.

Children with COVID-19 may be more likely to be asymptomatic than adults, with some studies estimating that as many as half of all children who develop COVID-19 don’t develop symptoms.

A 2021 study found that children and young adults have a low chance of developing fever or respiratory symptoms with COVID-19, but people who don’t have these symptoms can still pass the coronavirus to others.

The prevalence of asymptomatic COVID-19 seems to depend on the strain of the coronavirus and also on how much of the population is vaccinated.

Can the coronavirus still spread to others if you’re asymptomatic?

People with COVID-19 who don’t have symptoms can still pass the coronavirus to other people. Transmission of the virus can occur in asymptomatic or pre-symptomatic people.

According to the CDC, current evidence suggests that the majority of virus transmission occurs early in the illness — 1 or 2 days before symptoms arise or 2 to 3 days after symptom onset.

In another 2021 study, researchers created a model to estimate the percentage of virus transmissions from people without symptoms. They predicted that asymptomatic people made up at least half of transmissions.

In a small 2020 study, researchers observed the highest viral load in throat swabs at the time that symptoms first appeared, and estimated that infectiousness peaked on or before symptom onset. The researchers also estimated that 44 percent of COVID-19 infections came from people without symptoms.

In another study from the same year, researchers found that more than half of the residents at a skilled nursing facility were asymptomatic at the time they tested positive. The researchers concluded that unrecognized pre-symptomatic or asymptomatic transmission likely contributes to the spread of COVID-19 in these types of settings.

How do you know if you have COVID-19 if you’re asymptomatic?

If you don’t have COVID-19 symptoms but think that you may have been exposed, you should isolate yourself at home and take a COVID-19 test. A COVID-19 test can still reveal if you’re carrying the coronavirus even if you show no signs of illness.

It’s also important to get tested if you’ve been in a crowded place or have recently traveled, since these activities can put you at a higher risk of exposure.

The CDC recommends getting a COVID-19 test:

if you have symptoms of COVID-19
if you’ve had a suspected or known contact with someone who has COVID-19 in the past 5 days
for screenings at places like your workplace or school and at events with large gatherings (e.g. concerts)
before or after you’ve traveled
when asked to get tested by a healthcare professional or public health official

What steps do you need to take if you test positive for COVID-19?

On December 21, 2021, the CDC shortened its recommended time for isolation. It’s now recommended that people who test positive for COVID-19 isolate for 5 days.

If you’re asymptomatic or your symptoms improve — including not having a fever for 24 hours without fever-reducing mediation — you can end your isolation and wear a mask for another 5 days whenever you’re around others.

The bottom line

Many people who develop COVID-19 are asymptomatic, meaning they don’t develop symptoms. People with asymptomatic COVID-19 can still pass the virus to other people, and studies suggest that many transmissions come from people without symptoms.

If you suspect you’ve been exposed to COVID-19, it’s important to isolate and get tested to avoid transmitting the coronavirus to people around you. Even if you don’t feel sick, you can still transmit the virus to other people.

If you test positive for COVID-19, the CDC recommends isolating for 5 days and continuing to wear a mask when you’re around other people for an additional 5 days.

How we reviewed this article:

SourcesHistoryHealthline has strict sourcing guidelines and relies on peer-reviewed studies, academic research institutions, and medical journals and associations. We only use quality, credible sources to ensure content accuracy and integrity. You can learn more about how we ensure our content is accurate and current by reading our editorial policy.

Arons MM, et al. (2020). Presymptomatic SARS-CoV-2 infections and transmission in a skilled nursing facility. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7200056/
CDC newsroom. (2022).https://www.cdc.gov/media/index.html
Coronavirus disease (COVID): How is it transmitted? (2021).https://www.who.int/news-room/questions-and-answers/item/coronavirus-disease-covid-19-how-is-it-transmitted
COVID-19. (n.d.).https://www.cdc.gov/coronavirus/2019-nCoV/index.html
Johansson MA, et al. (2021). SARS-CoV-2 transmission from people without COVID-19 symptoms.https://jamanetwork.com/journals/jamanetworkopen/fullarticle/2774707
Ma Q, et al. (2021). Global percentage of asymptomatic SARS-CoV-2 infections among the tested population and individuals with confirmed COVID-19 diagnosis: A systematic review and meta-analysis.https://jamanetwork.com/journals/jamanetworkopen/fullarticle/2787098
Poletti P, et al. (2021). Association of age with likelihood of developing symptoms and critical disease among close contacts exposed to patients with confirmed SARS-CoV-2 infection in Italy.https://jamanetwork.com/journals/jamanetworkopen/fullarticle/2777314
Tan JK, et al. (2021). The prevalence and clinical significance of presymptomatic COVID-19 patients: How we can be one step ahead in mitigating a deadly pandemic.https://bmcinfectdis.biomedcentral.com/articles/10.1186/s12879-021-05849-7
Xi He, et al. (2020). Temporal dynamics in viral shedding and transmissibility of COVID-19.https://www.nature.com/articles/s41591-020-0869-5

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Medically reviewed by Elizabeth Thottacherry, MD — Written by Daniel Yetman on March 30, 2022

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