Key takeaways:
People are most contagious with COVID-19 on the fourth day of their illness.
Many people don’t get symptoms right away when they catch COVID, and some never experience symptoms at all. But, in both cases, people may still be contagious.
On average, people are contagious with COVID for 5 to 10 days. But some people stay contagious for longer.
Being sick with COVID-19 isn’t easy. On top of being sick, you may still need to isolate even if you only have mild COVID symptoms. While you’re contagious with COVID, staying home protects everyone in your community.
So, how can you decide when to start and end your isolation? And how do you know when it’s safe to go back to your usual routines? Here’s everything you need to know about when you’re most contagious with COVID, and how to figure out your COVID contagious period.
How long is someone with COVID infectious?
The short answer is that you’re contagious with COVID for about 8 to 10 days after you start showing signs of COVID illness or test positive for the COVID virus.
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The full answer is more complicated.
The 10-day mark seems to apply to people who have mild-to-moderate COVID illness. But
people with severe cases of COVID illness can remain infectious for several weeks or months. There’s also evidence that people with a weakened immune system remain contagious for longer periods of time, too.
On the other hand, some people stop being contagious before that 8-to-10-day mark. This seems to be the case for people who're fully vaccinated against COVID but get a COVID infection anyway. (This is called a “breakthrough infection.”) Studies show that vaccinated people who have breakthrough infections with the Omicron subvariants are contagious for a shorter period of time compared to unvaccinated people who get sick with COVID.
Experts don’t know exactly how long a vaccinated individual can spread the virus when they get sick with COVID. This is why isolation and “stay home” recommendations are the same for everyone, regardless of whether or not they received a COVID vaccine.
When are you no longer contagious with COVID?
You’re probably no longer contagious after 10 days if you have a mild COVID illness and your symptoms are getting better. After this point, you’re probably no longer shedding as much COVID virus.
Stop the spread: Even if you’re testing negative for COVID-19, it’s best to proceed with caution. Here’s how to keep yourself and your loved ones safe if you start experiencing COVID symptoms.
Feel better fast: There’s no magic cure for a COVID infection. But, if you want to reduce your symptoms quickly, certain over-the-counter (OTC) medications and at-home treatments may help.
How long does the virus live? Can the virus that causes COVID live on food, clothing, dishes, or other surfaces? Learn more about the true risk of viral contamination in your home.
But scientists are still learning more about how the Omicron subvariants behave. It’s possible that even people with mild illnesses and those who received a COVID vaccine may shed the virus for longer than 10 days.
On the other hand, if you have a severe illness or a weakened immune system, you can be contagious for much longer. This has been true throughout the pandemic and hasn’t changed, even with the emergence of new variants.
What is viral shedding?
Viral shedding happens when a sick person releases copies of a virus from their body. This happens when you:
Cough
Sneeze
Talk
Cry
Breathe
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Viral shedding is how viruses spread from person to person.
People are contagious with COVID as long as they’re shedding the virus. You can assume that you’re shedding the COVID virus if:
You have a fever.
You have COVID symptoms that haven’t gotten better yet.
But you can’t rely on symptoms alone to tell you if you’re shedding the virus. Some people who get sick with COVID never develop symptoms. But these people can still shed the virus, so they’re still contagious.
That’s why experts recommend taking a COVID test if you’ve been exposed to someone with COVID illness, even if you have no symptoms.
When are you most contagious with COVID?
People are most contagious during the days when their viral loads are very high. That’s because you will shed more virus when there are high levels of virus in your body.
Early in the pandemic, people were most contagious when their symptoms first started or even 1 to 2 days before their symptoms started. But that seems to have changed with the Omicron subvariants. Now, people are most contagious after they’ve developed symptoms of their COVID illness.
Research shows that people typically have the highest levels of the virus in their body — also called peak viral load — about 3 to 5 days after their COVID symptoms start. This is when they’re the most contagious and most likely to pass the virus to other people.
How contagious is COVID?
The COVID virus is very contagious, especially Omicron subvariants.
To determine how contagious a virus is, there’s something called a basic reproduction number. This is a measure of a virus’s ability to spread and infect other people. It’s noted as R0 and pronounced as“R-naught.”
A virus with a high R0 is more contagious than a virus with a lower R0. In studies, the original Omicron strain’s R0 is estimated to be about 8. Some studies report an R0 as high as 20. Though, thanks to widespread immunity, the effective R0 is closer to 3.5. That means someone who’s sick with COVID will likely get 3 to 4 other people sick, too (rather than 20).
That makes COVID much more contagious than seasonal flu. It’s also more contagious than Ebola and Zika, but not as contagious as measles.
It may take a few more years before scientists have a solid answer to the question of how contagious COVID is. But, for now, it’s clear that COVID is very contagious and spreads easily from person to person.
Isolation guidelines for preventing the spread of COVID
In the past, it could feel hard to know when you could stop isolating if you were sick with COVID. But the CDC has simplified the approach to isolation for people who're sick with COVID.
The CDC now recommends that people who are sick with COVID isolate until both of the following are true:
They’re fever-free without the help of medication for 24 hours.
Their symptoms are getting better.
Once you’ve hit these milestones, you can go back to work, school, and your normal routine. This applies to people who are up-to-date with COVID vaccines and those who aren’t.
You should isolate again if at any point your symptoms get worse again or your fever comes back.
If you’re vaccinated, are you still contagious if you get COVID?
People who are vaccinated against COVID can still get sick. They’re less likely to develop serious COVID illness. But they’re still contagious if they get sick with COVID.
Frequently asked questions
Mild-to-moderate COVID-19 illness can last anywhere from 1 to 14 days. People who are up-to-date with their COVID vaccines are more likely to develop mild illness and recover quickly. Their COVID infection may only last 1 day.
People who aren’t up-to-date with their vaccines are more likely to develop a longer illness. People with certain medical conditions or those with weakened immune systems may develop longer illness, too.
It’s possible to test positive for COVID and not be contagious. This happens in situations where people have already recovered from their COVID illness but continue to have positive tests. It’s very likely that you’re contagious if you test positive for COVID and have a fever or feel sick.
Long COVID is a condition that develops after a COVID illness. It can impact your health in many ways, but it isn’t contagious. You can’t give long COVID to someone else.
Mild-to-moderate COVID-19 illness can last anywhere from 1 to 14 days. People who are up-to-date with their COVID vaccines are more likely to develop mild illness and recover quickly. Their COVID infection may only last 1 day.
People who aren’t up-to-date with their vaccines are more likely to develop a longer illness. People with certain medical conditions or those with weakened immune systems may develop longer illness, too.
It’s possible to test positive for COVID and not be contagious. This happens in situations where people have already recovered from their COVID illness but continue to have positive tests. It’s very likely that you’re contagious if you test positive for COVID and have a fever or feel sick.
Long COVID is a condition that develops after a COVID illness. It can impact your health in many ways, but it isn’t contagious. You can’t give long COVID to someone else.
The bottom line
Most people with COVID-19 illness are contagious for about 10 days. People with severe illness or a weakened immune system can be contagious for longer. You’re most contagious on the third to fifth day of COVID illness.
Make sure to isolate until your symptoms are getting better and you’re fever free for 24 hours without the help of medication. Wear a mask, follow physical distancing guidelines, and wash your hands frequently for 5 days after you end your isolation. Restart the isolation process if your symptoms get worse or your fever comes back.
Why trust our experts?
References
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