The incubation period of SARS-CoV-2 — the virus that causes COVID-19 — varies from person to person. Once it replicates in your cells and reaches higher numbers, you may feel symptoms.

The incubation period is the time that it takes between when you’re exposed to the virus and when symptoms appear.

Read on to learn more about how long it may take for symptoms to develop, what types of symptoms need immediate medical attention, and how to protect yourself from the coronavirus.

An incubation period is the time between when you first contract a virus and when your symptoms start.

Incubation periods can vary widely depending on the type of virus. For example, the incubation period for the flu is short. The Centers for Disease Control and Prevention (CDC) says that it ranges from 1 to 4 days.

Conversely, the incubation periods for viral infections like mono and hepatitis B are much longer. The symptoms of mono can take 4 to 6 weeks to develop following exposure to the Epstein-Barr virus. Meanwhile, the incubation period for hepatitis B is even longer — ranging from 60 to 150 days.

Currently, according to the CDC, the incubation period for the coronavirus is somewhere between 2 and 14 days after exposure.

A report published earlier in the pandemic found that more than 97 percent of people who contract SARS-CoV-2 show symptoms within 11.5 days of exposure. The average incubation period was estimated to be around 5 days.

The incubation period appears to have shortened with the emergence of the Delta variant of SARS-CoV-2. This variant replicates at a faster rate and to higher numbers than previous strains of the coronavirus.

A September 2021 study compared the Delta variant to the original strain of SARS-CoV-2. Researchers found that the incubation period of the Delta variant was 4 days, which was 2 days shorter than the 6-day incubation period they observed for the original strain of SARS-CoV-2.


According to the CDC, the incubation period for the coronavirus is between 2 and 14 days after exposure. The average incubation period is estimated to be around 5 days after exposure to the virus.

A variety of potential symptoms have been observed in COVID-19. Research reviews have found that the most commonly recorded symptoms include:

Other recorded symptoms include:

How exactly COVID-19 symptoms present and in what order can vary from person to person.

An August 2020 study aimed to model the onset of COVID-19 symptoms.

To do this, researchers used data from two different groups of people with confirmed COVID-19. The first group was made up of 55,924 people. The second group was smaller, comprising 1,099 individuals.

Using their model, the researchers found that the COVID-19 symptoms they evaluated were likely to appear in the following order:

  1. fever
  2. cough
  3. sore throat, headache, muscle aches and pains
  4. nausea or vomiting
  5. diarrhea

However, it’s important to remember that you can still have COVID-19 and not progress through all of the above symptoms. For example, many people first notice a fever, but some may not ever develop a fever.

Others may develop a sore throat or runny nose without other symptoms. They may believe they have allergies or a cold, when it’s actually COVID-19.

According to the World Health Organization (WHO), about 80 percent of people experience a mild to moderate illness with COVID-19. In the majority of cases, people recover without needing any special medical treatment.

However, some people can become seriously or critically ill after developing COVID-19, including:

Early observations in China found that the time between symptom onset and more serious symptoms like difficulty breathing is 5 to 8 days. The CDC adds that some individuals can rapidly deteriorate about 1 week into their illness. They can potentially progress to acute respiratory distress syndrome, which is life threatening.

Seek emergency medical attention or call 911 if you or someone else is having symptoms like:

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SARS-CoV-2 spreads mostly from person to person through respiratory droplets that are transmitted when a person with the virus talks, laughs, sneezes, or coughs. When droplets containing the virus enter your nose, mouth, or eyes, you can contract the virus.

There’s also a possibility that someone who has the coronavirus can transmit the virus even if they don’t develop symptoms. This is called asymptomatic transmission.

A May 2021 study followed workers participating in a mass screening program for COVID-19. It found that asymptomatic individuals presented a significant risk for the virus to spread to their contacts.

It’s also possible to transmit the virus before you develop COVID-19 symptoms. This is called presymptomatic transmission. We’ll discuss this a little more in the next section.

You also don’t necessarily have to be in the company of someone who has the virus either. It’s possible for aerosols from a person with coronavirus to remain in the air, possibly for hours, after they’ve talked, coughed, or sneezed.

While this type of transmission is of concern, it’s probably only likely to happen in certain places, such as:

  • households or communal living situations like nursing homes, prisons, or dormitories
  • indoor spaces with poor ventilation
  • crowded or poorly ventilated areas where few people are wearing masks

It’s also possible that SARS-CoV-2 can be transmitted through touching surfaces that are contaminated with the virus and then touching your mouth, nose, or eyes. However, this isn’t the main way the coronavirus spreads.

Mask wearing can help slow the spread of the virus from people without symptoms or people who do not know they have contracted the virus. The CDC recommends that all people older than age 2 wear face masks in indoor public places when they’re:

  • not fully vaccinated
  • fully vaccinated, but in an area with high COVID-19 transmission
  • fully vaccinated, but have a weakened immune system

In general, mask wearing isn’t necessary outdoors. However, consider wearing a mask if you’re in a crowded outdoor area or are having close contact with others who aren’t yet fully vaccinated.

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The coronavirus is highly contagious, which means it spreads easily from person to person. This has only increased with the emergence of the Delta variant. According to the CDC, the Delta variant is more than two times as contagious as the original strain of the coronavirus.

A January 2021 study found that the amount of virus in the upper respiratory tract peaked during the first week of illness, with no live virus being detected after 9 days. That means that the virus is most contagious during this timeframe.

An August 2021 study drilled down further on when the virus is most contagious. It followed 730 people with confirmed COVID-19 and 8,852 close contacts.

The researchers found that people were at the highest risk of transmitting the virus to their close contacts over a 6-day period. This ranged from 2 days prior to symptom onset to 3 days after symptoms appeared. Risk peaked at day 0, just as symptoms were beginning.


Based on the research, if you have a coronavirus infection, the virus seems to be most contagious from 2 days before your symptoms start to 3 days after your symptoms appear.

If you’ve been exposed to the coronavirus, you may need to quarantine. What you need to do varies depending on whether or not you’re fully vaccinated.

What should you do if you’re unvaccinated and have been exposed to the coronavirus?

According to the CDC, people who haven’t been vaccinated should quarantine if they’ve had close contact with someone who has COVID-19. Close contact is defined as being within 6 feet (2 meters) of a person with COVID-19 for 15 minutes or longer during a 24-hour period.

A quarantine involves:

  • staying at home for 14 days after you were last around someone with COVID-19
  • keeping your distance from other people that you live with
  • monitoring yourself for symptoms of COVID-19

What should you do if you’re fully vaccinated and have been exposed to the coronavirus?

If you’re fully vaccinated, you don’t have to quarantine after being in close contact with someone with COVID-19 unless you develop symptoms. However, you should still:

  • Monitor yourself for symptoms of COVID-19.
  • Get tested 5 to 7 days after exposure.
  • Wear a mask while in indoor public spaces for 14 days or until your COVID-19 test comes back negative.

It’s important that some people contact their doctor promptly if they believe that they’ve been exposed to COVID-19, even if they’re fully vaccinated. These individuals include:

  • older adults
  • people with underlying health conditions that increase their risk of serious illness
  • those with a weakened immune system
  • pregnant people

There are treatments available, such as monoclonal antibodies, that can help prevent serious illness in higher risk individuals.

What if you have COVID-19?

If you have COVID-19, do the following:

  • Stay home and only leave to receive medical care.
  • Try to separate yourself as much as possible from others in your household.
  • Wear a mask when you need to be around other people.
  • Take care of yourself by staying hydrated or taking over-the-counter medications to alleviate symptoms.
  • Monitor your symptoms and seek medical attention if they begin to get worse.

According to the CDC, you can be around others again if all of the following are true:

  • It’s been at least 10 days since your symptoms started.
  • You’ve gone 24 hours with no fever (without the use of fever-reducing medications like acetaminophen or ibuprofen).
  • Your other symptoms have started to improve.

No vaccine is 100 percent effective. As such, even though the COVID-19 vaccines are highly effective at preventing COVID-19, it’s still possible to be fully vaccinated and contract the coronavirus. These are called breakthrough infections.

It’s still unclear exactly how common breakthrough infections are. One October 2021 study found that out of 1,497 fully vaccinated healthcare workers, 39 (2.6 percent) had documented breakthrough infections. Most of these infections were asymptomatic or mild.

The coronavirus can still be transmitted to others from fully vaccinated people that contract it. That’s why it’s still important for fully vaccinated individuals to continue to take everyday precautions to prevent the spread of COVID-19.

An October 2021 study examined the transmission of the Delta variant within households. It followed 231 contacts of 162 people with confirmed COVID-19 caused by the Delta variant. Researchers found that:

  • Vaccination lowered the risk of infection. Of vaccinated household contacts, 25 percent contracted the virus, compared to 38 percent of unvaccinated household contacts.
  • The virus can spread among vaccinated individuals. The Delta variant is transmitted from vaccinated and unvaccinated people with COVID-19 to household contacts at similar rates.
  • Vaccinated people clear the virus faster. Compared to unvaccinated people, viral loads in vaccinated individuals decreased at a more rapid rate.

The best way to prevent yourself from contracting the coronavirus is to get vaccinated. There are three COVID-19 vaccines available in the United States, including the:

Additionally, the CDC has recommended that everyone ages 18 and older should get a booster shot. Your booster can be any of the three COVID-19 vaccines available in the United States.

Those that received the Pfizer or Moderna vaccines can get their booster at least 6 months after receiving their second dose. Individuals who got the Johnson & Johnson vaccine can receive their booster at least 2 months after their initial vaccination.

Other ways to prevent COVID-19 include:

  • Wearing a mask. Wear a mask that comfortably covers your nose and mouth. This is particularly important if you are in an area with a high number of COVID-19 cases, have a weakened immune system, or are unvaccinated.
  • Washing your hands. Try to wash your hands often, particularly after being out in public and before touching your face, mouth, or eyes. Use soap and water and wash for at least 20 seconds. If you don’t have soap and water, use hand sanitizer with at least 60 percent alcohol.
  • Practicing physical distancing. Stay at least 6 feet (2 meters) away from those outside of your household.
  • Avoiding certain situations. Try to avoid large groups of people or being in poorly ventilated indoor spaces.
  • Cleaning high-touch surfaces. Regularly wipe down high-touch surfaces like doorknobs, keyboards, and stair rails in your home with household cleaners or a diluted bleach solution.

Contact tracing is a method that’s used to help slow the spread of infectious diseases like COVID-19. It involves identifying close contacts of people with confirmed COVID-19 and notifying them of a potential exposure.

If your community is using contact tracing, a public health worker called a contact tracer may contact you to inform you that a close contact has tested positive for COVID-19. This individual can also explain next steps, including testing and quarantine.

Any conversation with a contact tracer remains confidential. A contact tracer will keep your personal and medical information private. They’ll also never ask you for things like your Social Security number, bank account information, or credit card number.

Even if contact tracing is being used in your area, if you do contract COVID-19, it’s important to let your close contacts know as soon as possible. That way, they can plan to get tested and quarantine, if necessary.

Most people who develop COVID-19 start noticing symptoms within 2 to 14 days after being exposed to the coronavirus. On average, it takes about 5 days to develop symptoms. But this period may be shorter due to the emergence of the Delta variant.

The coronavirus is most contagious in the days immediately before and after symptoms come on. Additionally, it’s important to remember that fully vaccinated people can still potentially contract and transmit the virus to others.

If you’re concerned about a potential exposure, it’s a good idea to get tested for COVID-19. If you do develop symptoms, plan to stay home and avoid contact with other people until you recover.

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