How Long Is the COVID-19 Incubation Period?
Knowing when you may have come into contact with COVID-19 helps with testing and preventing the spread of the virus.
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Medically reviewed by Kashif J. Piracha, MD
The COVID-19 incubation period, or the time from exposure to symptom onset, lasts about two to 14 days. The average incubation period is five days, though the Omicron variant may cause symptoms within two to three days.
People are typically infectious and can spread the virus during incubation. Knowing when you came into contact with the virus may help you decide when to receive a test. Testing too late or too soon may result in a false negative.
Read on to learn about the COVID-19 incubation period and whether it affects the severity of your symptoms and the length of your illness.
What Is an Incubation Period?
The incubation period is the time from exposure to a virus to when you develop symptoms. The average COVID-19 incubation period depends on the variant. Pre-Omicron variants have an incubation period of two to 14 days, with an average of five days. In contrast, the Omicron variant has an incubation period of three to four days.
You usually do not develop symptoms right away when a virus infects you. It often takes time for the virus to replicate, or infect enough of your body's cells to make you sick.
"Even though you're already infected with the virus, you may not know you're ill during the incubation period," Melissa Hawkins, Ph.D., an epidemiologist and director of undergraduate programs in the department of health studies at American University, told Health.
Many tests only detect SARS-CoV-2, the virus that causes COVID-19, during specific points in the infection, usually when symptoms arise. Testing too late or too soon may result in a false negative, unknowingly causing infected people to spread the virus to others.
"Timing does really matter and can make a difference between a positive and a negative test," said Hawkins. "If you were negative in the morning, you could be positive later that day or the next day."
Related: How Long Does COVID-19 Last? What To Expect if You Contract the Virus
Are You Contagious During Incubation?
Research has found that you are contagious during the COVID-19 incubation period before showing symptoms. A study published in 2021 found that people with COVID-19 were most contagious two days before and three days after symptoms developed.
Most transmissions occur before people realize they are sick, said Hawkins. Anyone with COVID-19—regardless of symptoms, vaccination status, or variant type—can spread the virus to others.
The Centers for Disease Control and Prevention (CDC) advises taking the following steps if you recently had close contact with someone with COVID-19:
Wear a high-quality mask around others for 10 days.
Take a test five days after exposure, even if you do not have symptoms.
If you test positive, begin self-isolation right away. If you test negative, continue mask-wearing through day 10.
"Don't disregard a runny nose, sore throat, or headache because those are symptoms, especially after an exposure," said Hawkins.
Spreading the virus to others becomes less likely as the amount of infectious SARS-CoV-2 particles in your body decreases. The CDC reports that you are likely not contagious after 10 days if you had a mild illness. You can end your self-isolation after five days if your symptoms are improving and you are fever-free for at least 24 hours without using a fever reducer.
How Incubation Impacts Symptoms and Contagiousness
In short, no: How long a virus incubates before causing symptoms does not affect how long your illness lasts or how long you are contagious. Anyone can develop mild to severe symptoms, which typically develop within two to 14 days.
Instead, variables that may affect how severe your symptoms are include:
Age: People older than 50 are more likely to develop severe illness than others.
Health conditions: Certain chronic illnesses, like chronic obstructive pulmonary disorder (COPD) and obesity, may increase the risk of severe symptoms.
Past COVID-19 infection: You may have some protection against COVID-19 if you previously tested positive. Still, SARS-CoV-2 can reinfect you if you come into contact with a different variant, even if you have recently recovered from COVID-19.
Treatments: A healthcare provider may advise taking antiviral medicines if you have a high risk of developing severe illness. For example, Paxlovid (nirmatrelvir/ritonavir) can reduce the severity of COVID-19 if you start taking the medicine within five days of symptom onset.
Vaccination status: The CDC reports that COVID-19 vaccines reduce the risk of severe symptoms even if you become infected.
Weak immune system: People with a weak immune system or who take medicines that compromise the immune system may be more likely to have severe symptoms than others.
Still, two very similar vaccinated people may have different experiences with COVID-19.
"We know some of the key risk factors that are likely to result in severe illness, but it's still a bit of a mystery why one person in a household may get sick and another person may not," said Hawkins.
The severity of your symptoms may impact how long you are contagious. People with severe illness may be contagious for longer than 10 days. If you had severe symptoms, you may need to talk to a healthcare provider before ending isolation.
How To Protect Against COVID-19
Variants and increased cases can be discouraging, but continuing evidence-based safety measures is essential to protecting your health, said Hawkins.
"There's a lot of room to be able to engage in the activities and see people we want to see because we now have so many more effective tools to stay safe and mitigate the spread," said Hawkins.
Ways to protect yourself and others from COVID-19 include:
Cover your coughs and sneezes: Use the crook of your elbow or a tissue to keep infected droplets from spreading.
Distance: Avoid crowds, especially indoor spaces with poor ventilation, which increases the spread of COVID-19. Stay away from people who are sick, and stay home if you are sick.
Do not share personal items: Sharing bedding, cups, towels, and utensils without washing them in soap and water may spread COVID-19.
Vaccination: The CDC advises staying up to date with vaccination to protect yourself and others against severe illness, hospitalization, and death.
Wash your hands: Avoid touching your eyes, nose, or mouth without washing your hands. Use soap and water for at least 20 seconds before eating and preparing food. Wash your hands after blowing your nose, coughing, sneezing, and using the toilet. Use hand sanitizer with 60% alcohol or more if you do not have soap and water.
Wear a high-quality mask: Make sure you wear a fitted high-quality mask or respirator indoors or in crowded areas if there are many COVID-19 cases in your community, even if you are vaccinated. People who are not up to date on vaccination or with weak immune systems may need to wear a mask, no matter how many cases.
Related: What Are COVID-19 Signs and Symptoms in People of All Ages?
A Quick Review
The incubation period of a virus is how long it takes from being infected until symptoms show up. With COVID-19, you are contagious during the incubation period. Wear a high-quality mask around others for 10 days, and receive a test five days after exposure to avoid spreading the virus.'
The incubation period does not affect the severity and contagiousness of your symptoms. Instead, your age, health conditions, and vaccination status may affect the severity of your symptoms.
Frequently washing your hands, mask-wearing, and staying up to date on vaccination can help protect you and others from COVID-19.
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