How Long Are You Contagious With COVID-19?
Factors That Can Increase or Decrease Infectivity
Medically reviewed by Brian Bezack, DO
If you test positive for COVID-19, the duration of contagiousness can vary. This is because the virus can be shed (meaning released from the body through talking, exhaling, etc.) for anywhere from days to months depending on your age, vaccination status, immune status, severity of infection, and any preexisting conditions you may have.
Even so, the likelihood of transmission decreases as fewer viruses are shed over time. If you become infected with COVID-19, the Centers for Disease Control and Prevention (CDC) recommends that you isolate at home until you've been fever-free for 24 hours (without the held of medications). It's also recommended that you take additional precautions for five days following isolation.
This article explains how long COVID-19 is contagious and the variables that can increase or decrease the duration. It also offers tips on how to protect others if you or someone know gets COVID-19.
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Related: How to Isolate If You Have COVID-19
How Long Is Someone Contagious With COVID-19?
As a general rule, most people who get COVID-19 are no longer contagious 10 days after the appearance of symptoms or after testing positive for the virus. While there is significant variation in the risk of transmission, most cases follow the same general timeline once symptoms develop.
Early-Stage Contagiousness
When you are infected with COVID-19, the virus goes through what is called the incubation period. This is the time between exposure to the virus and the first appearance of symptoms. With COVID-19, the incubation period is generally two to three days following exposure.
During this period, viral particles will start to be shed through exhaling, talking, laughing, and other means. So, even if there are no symptoms, the infected person can still unwittingly transmit the virus to others. This is why the disease is so hard to control.
When symptoms do develop—and the number of viruses in the body (called the viral load) continues to increase—a person will be at their peak contagiousness and most able to transmit it to others.
When Is COVID-19 Most Contagious?
The current body of evidence suggests that the peak contagiousness of COVID-19 (and highest viral load for most people) is typically during the first few days of illness and when symptoms, including fever, are at their worst.
However, this shouldn't suggest that everyone with COVID-19 peaks at the same time or even that a drop in your viral load corresponds to a drop in viral shedding.
A 2023 study from Northwestern University found that people with COVID-19 exhale as many as 800 copies of the virus per minute during the first eight days after symptoms appear. So, even though the viral load may be dropping, infectious viral particles may continue to be exhaled.
This further reinforces the need for face masks and other preventive measures once any isolation period ends (after you've been fever-free for at least 24 hours without using fever-reducing medication).
Prolonged Contagiousness
There are situations in which the contagiousness of COVID-19 extends well beyond 10 days. According to the CDC, people with severe COVID-19 or those who are moderately to severely immunocompromised may remain contagious for longer.
Studies have repeatedly shown that the duration of viral shedding increases with the severity of the infection (such as when pneumonia or severe respiratory distress is involved). In such cases, the viral load can remain persistently high, increasing the duration of contagiousness to well over a month in rare instances.
If you are immunocompromised, the duration of contagiousness can be longer simply because it takes longer for the immune system to control the infection. While there is no rule as to how much longer that might be, a 2023 study in the journal Pathophysiology reported that immunocompromised people have a median viable viral shedding period of four weeks.
This includes people on chemotherapy, organ transplant recipients on immunosuppressants, and people with advanced untreated human immunodeficiency virus (HIV).
Related: When Is COVID-19 Most Contagious?
Are Certain Variants More Contagious?
Some COVID variants are more virulent (able to be passed) and pathogenic (able to cause illness) than previous strains. This is because, as the virus mutates, the mutations that are best able to survive are those that can escape immune detection.
When this happens, the immune cells that were once able to stop COVID-19 at the frontlines are less able to do so, increasing the risk of transmission.
An example of this is the Omicron variant first identified in 2021. Before Omicron, the peak contagiousness of the virus was two days before symptoms appeared and three days afterward, with viral shedding peaking on or before the appearance of symptoms.
With the emergence of Omicron, the peak of viral shedding was two to three days later.
It is possible—and perhaps likely—that future variants will become more virulent even if they aren't necessarily more pathogenic.
This is evidenced by the Delta variant, the 12th variant first seen in 2020. According to a study published in the Frontiers of Public Health, the duration of infectious shedding of the Delta variant was more than twice as long as the SARS-CoV-2 virus back in 2019.
Related: Incubation Period by COVID Variant
What If There Are No Symptoms?
It is estimated that more than 1 of every 3 COVID-19 infections in the United States are asymptomatic. This presents a significant public health challenge as viral shedding—and the spread of the virus—can still occur even in the absence of symptoms.
Is Asymptomatic COVID-19 Common?
According to research from the CDC, no less than 24% of all COVID-19 infections in the United States are the result of asymptomatic transmission.
Even so, asymptomatic infections tend to be less virulent than symptomatic infections, partly because the peak viral load tends to be lower. In some cases, the duration of contagiousness may be no longer than three days.
Concerning infectious shedding, the average duration is nine days for someone symptomatic for COVID-19 vs. only six days for someone asymptomatic for COVID-19.
Is Contagiousness Different in Children and Adolescents?
Generally, COVID-19 infections in children and adolescents cause less severe illness and fewer deaths than in adults. Research suggests that children may also be less susceptible to COVID-19 infection.
According to a 2021 review of studies involving 41,640 children and 268,945 adults, the risk of COVID-19 transmission was 56% less to kids than to adults. Even within the same household, children are nearly 60% less likely than adults to get COVID-19 from another family member.
Among the possible explanations for this, children seem to harbor fewer receptors for COVID-19—called angiotensin converting enzyme-2, or ACE-2, receptors—in their upper respiratory tracts. These receptors are proteins on cells to which viral particles attach and infect the cell. As children grow into adulthood, the number of receptors increases, providing the virus more targets for infection.
This doesn't mean that a child with COVID-19 is any less able to pass the virus than adults.
COVID-19 Transmission From Kids
According to a study in the Journal of Allergy and Clinical Immunology, which monitored 1,394 families from 2020 to 2021, children were actually more likely to transmit COVID-19 than other members of their households.
This was explained by the fact that 75% of the children were asymptomatic for COVID-19 and may have unknowingly spread the virus through nasal secretions and hand-to-nose behaviors.
Does Vaccination Reduce Contagion?
COVID-19 vaccination not only decreases your risk of infection and severe illness, but it may also significantly reduce your contagiousness.
A 2022 study published in JAMA Network Open was one of several that showed that fully vaccinated people have a shorter duration of infectious viral shedding—as well as a lower risk of transmitting it to others—than either partially vaccinated or unvaccinated people.
The study, which involved high-risk healthcare workers, hospital patients, and caregivers, found that the duration of contagiousness was roughly 10 days for unvaccinated people and eight days for partially vaccinated people—but only four days for fully vaccinated people.
Related: COVID Boosters: What You Need to Know
When Do You Need to Isolate?
The current CDC guidance for COVID-19 isolation depends on your symptoms. The CDC recommends that you:
Isolate at home until you've been fever-free for 24 hours (without taking fever-reducing medication) AND your symptoms are mild and improving.
Take additional precautions for five days following isolation, such as wearing a well-fitting mask, keeping a distance from others, and washing your hands often.
Related: How Common Is Long COVID?
How to Protect Other People
Health experts generally agree that COVID-19 is here to stay and that continued vigilance is needed as new variants and outbreaks emerge.
To protect yourself and others from this highly contagious virus, the CDC recommends the following preventive measures:
Keep up to date with your COVID-19 vaccines.
Stay at home and isolate if you have a fever.
Get tested if you have COVID-19 symptoms or believe you were exposed to COVID-19.
Avoid contact with people you know or suspect have COVID-19.
Wear a face mask if you are isolating for COVID-19 but need to be around others.
Wear a face mask if you need to be around someone in your household who has COVID-19.
Seek treatment if you have COVID-19 and are at risk of severe illness.
Related: How COVID-19 Is Treated
Summary
The contagiousness of COVID-19 can vary, but people with mild or asymptomatic illness are usually no longer contagious after 10 days. People with moderate to severe illness or who are moderately to severely immunocompromised may remain contagious for 10 to 20 days or even longer.
Read the original article on Verywell Health.
