What Is the Incubation Period for the Flu, and When Is It Contagious? (2024)

This period of time before you get symptoms of infection is called the incubation period. In cases of the flu, this is usually between one and four days.

Influenza, often just called the flu, is a respiratory illness that’s caused by a virus. It’s contagious, meaning it spreads from person to person.

While influenza viruses can circulate year-round, they’re more common in the fall and winter months of the year. This period is referred to as the flu season.

But once you get the virus, how long does it take to start feeling flu symptoms? Read on to learn more about how the flu develops and when it becomes contagious.

While the general incubation period for the flu is usually between one and four days, this period can vary from person to person. The average incubation period for the flu is two days.

This means that, on average, people start to develop flu symptoms about two days after coming into contact with the influenza virus.

Several things can influence how long the incubation period is for the flu, including:

  • Infectious dose. This is the amount of virus you’ve been exposed to. Coming into contact with a larger amount of virus particles can shorten the incubation period.
  • Route of infection. This refers to the way the virus enters your body. Some routes of infection are more efficient than others, which can either increase or decrease the incubation period.
  • Pre-existing immunity. If you’ve been exposed to a certain virus before, your immune system may recognize it earlier, which can shorten the incubation period.

Once you have the influenza virus, you can spread it to other people about a day before you first notice symptoms.

Remember, the average incubation period for the flu is about two days. So, if you come into contact with virus on Saturday morning, you can potentially start spreading it to others by Sunday evening. And by Monday afternoon, you’ll likely start feeling the dreaded body aches that come with the flu.

Viral shedding refers to the release of the virus from your body into your surrounding environment. It tends to peak during your first day experiencing symptoms. This means you’re usually most contagious on this day. Once you develop symptoms, you’ll still be contagious for another five to seven days.

Children, older adults, and those with a weakened immune system may be contagious for a longer period of time.

It’s often hard to know when you have the flu coming on. Unlike the symptoms of the common cold, which develop gradually, the symptoms of the flu often come on suddenly.

The common symptoms of the flu can include:

  • fever
  • headache
  • stuffy nose
  • sore throat
  • dry cough
  • aches and pains
  • chills
  • feeling fatigued, tired, or weak

Children may also experience nausea, vomiting, or ear pain when they have the flu.

Symptoms of the flu typically last anywhere from three to seven days, thought you might feel lingering fatigue or weakness for up to two weeks. Learn more about how long the flu lasts.

The flu mostly spreads through respiratory particles that are released when your cough and sneeze. If you have the flu and sneeze in a crowded area, those around you can inhale the particles of your sneeze and get the virus.

The virus can also be transmitted through coming into contact with objects or surfaces, such as a door handle or keyboard, that are coated in these respiratory particles. If you touch a contaminated object and then touch your eyes, nose, or mouth, you may get the flu.

If you already have the flu, there are a few things you can do to reduce your risk of passing it to others:

  • Stay home. The flu is extremely contagious, so it can spread quickly in crowded settings, such as schools and offices. Try to limit your contact with others until you’ve been fever-free for at least 24 hours.
  • Wash your hands. Wash your hands with soap and warm water often, especially after coughing, sneezing, or touching your face. If soap and water aren’t available, use an alcohol-based hand sanitizer.
  • Cover your mouth and nose. When you sneeze or tough, try to do so into a tissue or the crook of your elbow to reduce the spread of respiratory particles. Make sure to quickly throw away any used tissues.

The flu is a highly contagious respiratory infection that’s common in the colder months of the year. Once you’ve encountered the virus, it can take between one and four days to develop symptoms. Once you have the virus, you’ll be contagious starting about a day before you notice symptoms.

If you want to avoid the flu altogether, the Centers for Disease Control recommends getting the seasonal flu shot as your best bet. Here’s a look at the pros and cons of the flu shot.

What Is the Incubation Period for the Flu, and When Is It Contagious? (2024)


What Is the Incubation Period for the Flu, and When Is It Contagious? ›

When Are People with Flu Contagious? Flu viruses can be detected in most infected persons beginning one day before symptoms develop and up to five to seven days after becoming sick. People with flu are most contagious during the first 3 days of their illness.

How soon before symptoms are you contagious with flu? ›

Most healthy children and adults with the flu can infect others beginning about one day before developing any symptoms and up to seven days after the symptoms resolve. People with weakened immune systems can remain contagious for up to several weeks.

How long does it take for someone to catch the flu from you? ›

The time from when a person is exposed and infected with influenza virus to when symptoms begin is about two days, but can range from about one to four days.

Can you be around someone with the flu and not get it? ›

Even if you try your best to stay healthy when someone in the house has the flu, there's still a chance that you'll become infected. The flu causes symptoms that range from mild to severe, and if you live with certain medical conditions such as heart disease, getting the flu can increase your risk of complications.

How long after being exposed to someone with the flu will you get it? ›

You can start to feel sick about 1 to 7 days after you come in contact with the virus. Most of the time, symptoms appear within 2 to 3 days. The flu spreads easily. It can affect a large group of people in a very short amount of time.

How to prevent the flu after being exposed? ›

It's important to self-isolate, wear a mask, and practice good hygiene while waiting for your test results. There's no cure for the flu. But if you're exposed to the virus and see a doctor early, you might be able to receive a prescription antiviral medication such as Tamiflu.

Can you catch the flu by standing next to someone? ›

Another great idea: Keep your germs to yourself!

Flu germs spread from person to person by way of coughing, sneezing or simply talking. That's because droplets from an infected person get into the air and are inhaled by people nearby. Anyone within three feet can easily be infected.

When do flu symptoms peak? ›

Symptoms generally appear within a few days of infection. They usually peak between days 2 and 4, and most people feel better after 5–7 days.

Should I take Tamiflu if exposed to flu? ›

If you have already been exposed to the flu, but you don't have any symptoms, you can take Tamiflu for up to 6 weeks to help prevent you from getting sick.

What is the incubation period of the flu? ›

In temperate climates, seasonal epidemics occur mainly during winter, while in tropical regions, influenza may occur throughout the year, causing outbreaks more irregularly. The time from infection to illness, known as the incubation period, is about 2 days, but ranges from 1–4 days.

How long does the flu virus live in the air? ›

According to a 2018 study, infectious flu droplets can remain in the air for at least one hour. Cold and flu viruses can spread through the air via respiratory secretions from infected people. These virus particles most commonly spread through the air when infected people sneeze or cough.

Is flu A or B worse? ›

Type A influenza is generally considered worse than type B influenza. This is because the symptoms are often more severe in type A influenza than in type B influenza. Type A influenza is more common than type B influenza. Researchers suggest that most adults have considerable immunity against type B influenza.

When is the flu most contagious? ›

When Are People with Flu Contagious? Flu viruses can be detected in most infected persons beginning one day before symptoms develop and up to five to seven days after becoming sick. People with flu are most contagious during the first 3 days of their illness.

How long is the isolation period for the flu? ›

Note: Not everyone with flu will have a fever. People with suspected or confirmed flu, who do not have a fever, should stay home from work at least 5 days after the onset of symptoms. People with flu are most contagious during the first 3 days of their illness.

Which flu is most common right now? ›

Influenza A is the most common strain and usually causes seasonal flu outbreaks. Influenza B can also cause flu outbreaks, but it mutates more slowly.

Are you contagious with a virus before you show symptoms? ›

How long is the common cold contagious? The cold can be spread for up to two weeks, including before symptoms even appear. In fact, you will have the ability to spread the cold virus to others for a few days before your symptoms begin. That's why we see it “go through” households.

How soon after exposure are you contagious? ›

It's possible to become contagious with COVID-19 on the same day you are exposed. Most people who get sick with COVID begin noticing symptoms about 2 to 14 days after exposure. But viral shedding can begin right away. That's why it's possible to spread the virus that causes COVID even before your symptoms start.

How long does it take to get sick from someone? ›

Once you catch a cold from someone else, it can take two or three days before you begin to feel symptoms. If someone you know has a cold, try to avoid or limit contact with them. You are most likely to catch a cold from them in the first few days that they are sick. That's according to the American Lung Association.

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