What is the Incubation Period for the Flu?

Published July 2nd, 2022 by Chris Riley
Fact Checked by
Jacqueline Hensler
Medically Reviewed:
Dr. Angel Rivera

What is the flu | Flu Spread | Incubation Period | Treatment

The flu is a highly contagious viral infection that can cause fever, body aches, and respiratory problems.

The incubation period of the flu is the time between when you are exposed to the virus and when you start to experience symptoms.

The flu becomes contagious during this time and can be spread to others.

There are a number of treatment options available for the flu, including prescribed medications and over-the-counter drugs which we will detail below.

In addition to the incubation period and treatment options, we will discuss how the flu spreads, its symptoms, and provide you with tips on how to prevent it.

What is the flu?

The flu, or influenza, is a respiratory illness caused by a group of flu viruses.

The viruses that cause the flu are very contagious and can easily spread from person to person.

It can cause mild to severe illness and is different from the common cold because the flu normally has more severe symptoms than cold symptoms.

The three different types of human influenza viruses are influenza A, B, and C.

Both influenza type A and type B can cause mild to severe symptoms and are very common.

Influenza type C is rarer and usually only causes mild symptoms. Flu season in the United States normally peaks from December until February but runs from October until May.

couple with the flu during the incubation period

How does the flu spread?

The flu virus is spread through the air by respiratory droplets that are released when you cough, sneeze, talk, or sing.

These droplets that contain the flu virus can be inhaled by someone else or land in their mouths, nose, or eyes which will infect them with the influenza virus.

It can also be passed on by touching something that has the flu virus on it and then touching your mouth, nose, or eyes.

The flu virus can live on hard, nonporous surfaces for up to 48 hours and lasts for 8-12 hours on cloth, paper, or tissue.

What is the incubation period of the flu?

The incubation period of the flu is when you have been infected by the flu virus but have not developed symptoms yet.

For the flu, it is normally between one to four days from the time of infection although initial symptoms usually show on the second day on an average incubation period.

The flu's incubation period means that you can spread it to other people even before you develop symptoms as it is still a contagious period.

When does the flu become contagious and for how long?

You are most contagious with the flu the first three to four days of having symptoms but can still be contagious for up to a week after your symptoms start.

The reason you are most contagious those first several days is that those days are when symptoms are usually the worst and you are more likely to cough and sneeze.

If you have a weakened immune system or are above the age of 65, you can still be contagious with the flu for longer than a week.

Children can also be contagious for longer due to having weaker immune systems than healthy adults.

You are no longer contagious with the flu when you have not had a fever for 24 hours without the aid of fever-reducing medications.

What are the symptoms of the flu?

There are numerous flu symptoms and they can range from mild to severe.

It is also possible to have the flu and be asymptomatic although it is not common. The common symptoms of the flu include:

  • Fever
  • Chills
  • Headache
  • Muscle pain and body aches
  • Tiredness and fatigue
  • Sore throat
  • Dry cough
  • Runny nose
  • Stuffy nose
  • Loss of appetite

The onset of symptoms is rapid and they usually appear suddenly.

The fever is normally the first symptom to show and can last for a few days while the other symptoms will follow and can last up to two weeks.

It is also more common for young children to experience vomiting, nausea, and diarrhea although adults may also get these symptoms too.

If the symptoms become severe or the flu is left untreated, it can lead to complications such as bacterial pneumonia, sinus infections, ear infections, myocarditis (inflammation of the heart), and encephalitis (inflammation of the brain). 

What are the treatment options for the flu?

There are many different treatment options for the flu, but the most important thing is to get plenty of rest, drink lots of fluids, and take over-the-counter ibuprofen (Advil, Motrin) or acetaminophen (Tylenol) to help reduce your fever.

If you are a healthy adult, you most likely will not need to seek medical attention and can recover from the flu in your own home.

However, if your symptoms become severe or you are at a higher risk for developing complications from the flu, your doctor may prescribe antiviral medications.

There are currently four different antiviral drugs approved by the Centers for Disease Control and Prevention (CDC) which can help to shorten the duration of the flu and make the symptoms less severe.

These drugs work best if they are started within 48 hours of when your symptoms first start. The antiviral medicines you may be prescribed include:

  • Oseltamivir (Tamiflu)
  • Zanamivir (Relenza)
  • Peramivir (Rapivab)
  • Baloxavir marboxil (Xofluza)

If you have a severe case of the flu or are at risk for complications, your doctor may also prescribe a steroid medication such as prednisone to help reduce the inflammation in your lungs.

If you have a fever, it is important to drink lots of fluids to stay hydrated as fevers can cause dehydration, vomiting, and diarrhea.

It is also important to see your doctor if you have any other underlying chronic medical conditions such as a respiratory disease (asthma, cystic fibrosis, chronic obstructive pulmonary disease), diabetes, or heart disease as the flu can worsen these chronic conditions.

What are the best ways to prevent getting the flu?

The best way to prevent getting the flu is by getting a flu vaccine every year.

The CDC recommends that everyone aged six months and older needs to get a flu vaccine annually as the vaccine is updated every year to include the most likely flu strains to affect the population that flu season.

The flu vaccine is most effective when it is given before the start of the flu season which is typically in October.

However, even if you get vaccinated later in the season, it can still be beneficial as the flu season can last until May.

The annual flu vaccine is usually administered as a flu shot although there is now also a nasal spray flu vaccine available.

In addition to getting a flu vaccine, there are other things you can do to help prevent the spread of the flu such as:

  • Frequent handwashing with soap and water or using an alcohol-based hand sanitizer
  • Avoiding close contact with sick people and wearing a mask around them if you must be in close proximity and practicing social distancing
  • Staying home from work, school, or other public places if you are sick
  • Covering your mouth and nose with a tissue, sleeve, or crook of your elbow when you cough or sneeze instead of your hands
  • Avoiding touching your eyes, nose, and mouth as this is how the flu virus can enter your body
  • Cleaning and disinfecting high-contact surface areas such as light switches, door knobs, faucet handles, phones, remote controls, etc.

It is also recommended to eat a healthy diet and exercise regularly to keep your immune system as strong as possible.

Summary

The incubation period for the flu is typically between one to four days which means that you can be contagious and spread the virus to others before your symptoms start.

The CDC recommends staying home if you have the flu for at least 24 hours after your fever has gone down without the use of medication.

If you have the flu and must be around others, it is recommended that you wear a face mask to help prevent the spread of the virus.

Treatment options for the flu include rest, staying hydrated, and using over-the-counter medications for your flu symptoms.

Prescription antiviral medications are available from your doctor if your symptoms are severe or you are at a higher risk of complications from the flu.

The best way to prevent the flu is to get an annual flu shot or nasal spray and follow the list of tips above.

If you have any more questions about the flu or its incubation period, please talk to your doctor or health care provider.

References, Studies, and sources:

NIH

Healthline

CDC

Johns Hopkins Medicine

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