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.

An incubation period is the time between when you’re first exposed to the virus and the onset of symptoms.

This article examines the incubation period of the virus that causes COVID-19, including how long it may take for symptoms to develop, what types of symptoms need immediate medical attention, and how to protect yourself.

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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% 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.

Incubation periods (and symptoms) may change with new COVID-19 variants.

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.

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:

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How COVID-19 symptoms present and in what order can vary from person to person. They can also vary according to the variant you’ve been exposed to.

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 consisted of 55,924 people, while 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), most 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:

According to the CDC, symptoms may start as mild but then progress to more severe. Some individuals can rapidly deteriorate within 1 week into their illness, potentially progressing to acute respiratory distress syndrome, which is life threatening.

When to seek emergency help

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

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.

Benefits of wearing a mask

According to the CDC, mask wearing can help slow the spread of the SARS-CoV-2 virus from people without symptoms or people who do not know they have contracted the virus.

When a person with an infection wears a mask, it reduces the spread of the virus to others. A mask also protects the wearer from breathing in infectious particles from those around them.

If you’re considering wearing a mask, this article provides information about the different types of masks and which are most effective.

The coronavirus is highly contagious, which means it spreads easily from person to person. This has only increased with the emergence of the Delta and Omicron variants.

According to a 2022 study, the Delta variant is associated with higher viral loads in both vaccinated and non-vaccinated people, more transmissibility, and higher hospitalization rates than 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.

The CDC has changed its recommended isolation or quarantine periods for COVID-19. The updated recommendations are now based on symptoms and not testing.

Previous isolation guidelines for COVID-19 recommended a minimum quarantine period of 5 days plus a period of post-isolation precautions.

The updated CDC guidelines recommend that people stay home and away from others for at least 24 hours after their symptoms have improved and they are no longer experiencing a fever (without using fever-reducing medication).

The guidance also encourages people to use precautions over the next 5 days after their quarantine is over. This is because they may still be contagious. Precautions include:

  • following good hygiene practices
  • wearing a mask
  • keeping your distance from others

As part of its new guidance, the CDC considers COVID-19 testing an option during the 5 days after isolation.

COVID-19 at-home testing kits can provide an approximation of whether a person is still contagious, but the CDC recognizes that repeated testing throughout the course of illness is not practical for many people.

Special considerations for those at high risk for severe illness

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.

Other treatments include antiviral therapies such as:

No vaccine is 100% effective. 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%) had documented breakthrough infections. Most of these infections were asymptomatic or mild.

Coronavirus can still be transmitted to others from fully vaccinated people who contract it. That’s why it’s still important for fully vaccinated individuals to continue taking 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% contracted the virus, compared to 38% 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. Currently, there are three COVID-19 vaccines available in the United States:

Updated vaccine recommendations for 2025

The Centers for Disease Control and Prevention (CDC) recommends that most people ages 18 years and older get an annual COVID-19 vaccine. They suggest a shared decision model for those ages 6 months to 17 years.

The American Academy of Pediatrics (AAP) recommends vaccination for every child 6 months or older, and the American College of Obstetricians and Gynecologists (ACOG) recommends vaccination for all pregnant people.

Primary vaccine series

The CDC recommends that most people receive a primary series of vaccines. This set of vaccines provides broad protection against the SARS-CoV-2 virus.

To complete the series, you must get all the doses in the set. The World Health Organization recommends an interval of 8 to 12 weeks between primary vaccine doses.

You should also get all of your primary doses from the same set. For example, if you received one dose of the Moderna vaccine, you’ll typically receive a Moderna vaccine for all of your primary doses.

Booster doses

Once you’ve finished your primary vaccine series, you’re eligible for a booster shot. These boosters are updated each year to target specific Omicron variants.

The 2024-2025 booster shots include:

  • 2024–2025 Moderna COVID-19 Vaccine: Anyone 6 months and older
  • 2024–2025 Pfizer-BioNTech COVID-19 Vaccine: Anyone 6 months and older
  • 2024–2025 Novavax COVID-19 Vaccine: Anyone 12 years and older

It’s worth noting that booster shots don’t need to match your primary vaccine. In other words, you can get a Novavax booster shot if you received Pfizer or Moderna vaccines for your primary series.

You are considered fully vaccinated if you’ve received the most recent booster.

Why a yearly COVID-19 vaccine is important

Getting a yearly COVID-19 vaccine is important because:

  • The COVID-19 vaccine protection decreases with time.
  • Immunity after a COVID-19 infection decreases with time.
  • COVID-19 vaccines are updated each year to protect against the most current variants.
  • The COVID-19 vaccine can lower your risk of long COVID.

According to the CDC, COVID-19 vaccines are especially important for people who are:

  • 65 years or older
  • are at high risk for severe COVID-19
  • are living in a long-term care facility
  • are pregnant, breastfeeding, trying to get pregnant, or planning to become pregnant in the future

Other ways to prevent COVID-19

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.

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. This period may be shorter due to the emergence of different variants.

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.