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Still contagious?

“It’s been more than a month, and I still can’t taste or smell. Am I still contagious?”

“My coworker is back at work after being home for a week and a half, but I can hear her coughing. Is she still contagious?”

“I never got very sick after testing positive, but three weeks later, I still feel slightly congested. Am I still contagious?”

“My boss wants me to have a negative test before I come back to work. But it’s been more than five weeks, and I’m still testing positive. Am I still contagious?”

Illustration of a person wearing a PPE mask and peeking out from a doorway with yellow and black caution tape stretched across it

We get questions like these every day. Even as the pace of vaccination picks up, the virus continues to spread. Over the last week, the country recorded well over 350,000 new cases of COVID-19. People continue to get sick. Fortunately, most will get better.

But when does a person stop being contagious? At what point can an individual who has tested positive, with or without symptoms, come out of isolation and resume normal activities without fear of spreading the virus to others? How long does one need to self-isolate?

CDC guidelines give a straightforward answer: You’re in the clear after 10 full days.

Assuming that…

  1. You were not severely ill. As a general rule, this means that you were not sick enough to be hospitalized or to need supplemental oxygen. (Read more about how experts classify severity of COVID-19 illness.) Note: Individuals who were severely ill may be told to self-isolate for up to 20 days after symptom onset.
  2. You have been fever-free for at least 24 hours (without taking fever-lowering medications) before leaving isolation.
  3. Any remaining symptoms you have are improving (not including possible loss of smell and taste).

So, how do you count those 10 days? If you never develop symptoms, start counting from the date of your positive test. If you have symptoms, start counting from the date the first symptom appeared, no matter when you were tested. In other words, if you lost your sense of smell on Monday and tested positive on Thursday, your 10-day countdown starts from Monday.

Just remember, the date of your positive test (if you don’t develop symptoms) or the date of your first symptom is Day Zero, and you must complete 10 full days of self-isolation. That means that you are free to go on Day 11.

How do we know 10 days is long enough? Because researchers at the CDC and elsewhere have failed to successfully culture viral particles obtained from individuals more than nine days after their symptoms began. In fact, according to the CDC, “the statistically estimated likelihood of recovering replication-competent virus approaches zero by 10 days.” Replication-competent virus is virus that can infect cells and reproduce itself to make additional infectious particles. Individuals who are not shedding replication-competent virus are not infectious and cannot transmit the virus to others.

But what if someone still tests positive after 10 days? This is very common. People who have tested positive for COVID-19 are very likely to continue to test positive after 10 days. But they are not contagious.

People who have tested positive or who have been sick with COVID-19 often continue to test positive for up to three months. Even after your immune system neutralizes a virus (COVID-19 or almost any other virus), bits and pieces of the virus’s genetic material remain in your body — like DNA evidence left at a crime scene. These little viral remnants degrade over time. They can’t harm you, and they can’t infect anyone else, but they can cause you to continue to test positive. The CDC recommends that people not be retested for 90 days unless they have new symptoms. Your employer should not require that you test negative in order to go back to work.

What if the person is still tired, coughing, congested, or has other symptoms? This is also very common. People often have a cough, feel unusually fatigued, or even experience some shortness of breath for at least several weeks after a mild to moderate case of COVID-19. But they are no longer contagious. These symptoms should improve steadily, but it can take time.

What if my sense of taste or smell has not returned? Unfortunately, this is also very common. In some cases, it takes months before an individual regains their sense of smell and/or taste, even partially. At this point, there is no proven treatment and no guarantee of full recovery. But this doesn’t mean you are still contagious.

Having COVID-19 is scary. Symptoms that linger for weeks or months can feel like a constant reminder of the infection, and it’s understandable to worry that each cough has the potential to infect others. Even when you don’t have symptoms, it makes sense to be worried that you could be putting others in danger. Fortunately, research has demonstrated repeatedly that after 10 days of isolation, individuals with mild to moderate cases of COVID-19 are not at risk of spreading the virus to others. While it’s important to continue to take precautions, like wearing masks, avoiding crowds, and keeping your distance, you should feel free to resume your normal activities.

This news story has not been updated since the date shown. Information contained in this story may be outdated. For current information about MIT Medical’s services, please see relevant areas of the MIT Medical website.