What is the flu in children?

Updated for the 2024-2025 flu season

Influenza (flu) is a very contagious viral infection that affects the air passages of the lungs. It causes a high fever, body aches, a cough, and other symptoms. It's one of the most severe and common viral illnesses of the winter season. Most children are ill with the flu for less than a week. But some children have a more serious illness and may need to be treated in the hospital. The flu may also lead to lung infection (pneumonia) or death.

Because of other illnesses such as COVID-19 and RSV, the CDC says getting a flu vaccine is more important than ever to protect yourself and the people around you from flu. Flu vaccines and other vaccines can be given at the same time. Talk with your healthcare provider about vaccines.

What causes the flu in a child?

The flu is caused by flu viruses. Flu viruses are divided into 3 types:

• Influenza types A and B. These 2 types of viruses cause widespread illness (epidemics) almost every winter. They often lead to more people needing to go to the hospital, and more people dying from the flu. Public health officials focus on stopping the spread of types A and B. One of the reasons the flu remains a problem is because the viruses change (mutate) often. This means that people are exposed to new types of the viruses each year.

• Influenza type C. This type of virus causes a very mild respiratory illness. It rarely causes epidemics. It does not have the severe public health impact that influenza types A and B do.

A flu virus is often passed from child to child through sneezing or coughing. The virus can also live for a short time on surfaces. This includes doorknobs, toys, pens or pencils, keyboards, phones and tablets, and countertops. It can also be passed through shared eating utensils and drinking. Your child can get a flu virus by touching something that was touched by an infected person, and then touching their mouth, nose, or eyes.

People are most contagious with the flu 24 hours before symptoms start, and while symptoms are most active. The risk of infecting others often ends about day 5 to 7 of the illness. Because the flu can be spread before symptoms start, it’s easy to pick up a flu virus. This is especially true with children, who often touch many surfaces and then touch their mouth, nose, or eyes.

Which children are at risk for the flu?

A child is at greater risk for the flu if they:

• Are around people infected with the flu

• Haven't had the flu vaccine

• Don't wash their hands after touching infected surfaces

Young children and children with certain underlying health conditions are at increased risk for a hospital stay or severe or complicated influenza infection. 

What are the symptoms of the flu in a child?

The flu is a respiratory disease, but it can affect the whole body. A child can become suddenly ill with any or all of these symptoms:

• Fever, which may be as high as 103°F (39.4°C) to 105°F (40.5°C)

• Body aches, which may be severe

• Headache

• Sore throat

• Cough that gets worse

• Tiredness

• Runny or stuffy nose

In some cases, your child may also have symptoms such as:

• Nausea

• Vomiting

• Diarrhea

Most children recover from the flu within a week. But they may still feel very tired for as long as 3 to 4 weeks.

It’s important to note that a cold and the flu have different symptoms:

A cold is usually mild and often goes away after a few days. The flu can cause severe symptoms and lead to problems such as pneumonia and even death. Many flu symptoms may be caused by other health problems. Make sure your child sees their healthcare provider for a diagnosis.

How is the flu diagnosed in a child?

The healthcare provider will ask about your child’s symptoms and health history. They will give your child a physical exam. The symptoms are often enough to diagnose the flu. Other tests may be done such as a nose or throat swab. This depends on your child’s symptoms and overall health. 

How is the flu treated in a child?

Treatment will depend on your child’s symptoms, age, and general health. It will also depend on how severe the condition is. The goal of treatment is to help prevent or ease symptoms.

Treatment may include medicines such as:

• Acetaminophen. This is to help lessen body aches and fever. Don't give aspirin to a child with a fever.

• Antiviral medicine. This may help to ease symptoms and shorten the length of illness. The medicine can lessen the chance of developing an ear infection from the flu. It may also help decrease other complications, including the need for hospitalization. The medicine is most useful if started within 2 days after symptoms start. But it may be started later if the child is having complications or is at high risk for them.

Antibiotics aren’t effective against viral infections, so they are not prescribed. They may be used, though, if your child has developed bacterial pneumonia. Otherwise, treatment focuses on helping ease your child’s symptoms until the illness passes.

Talk with your healthcare providers about the risks, benefits, and possible side effects of all medicines.

Also make sure your child:

• Gets lots of rest in bed

• Drinks plenty of fluids

What are possible complications of the flu in a child?

The flu can cause severe breathing problems. A child with severe symptoms may need to stay in the hospital. The flu can lead to a lung infection called pneumonia. In some cases, the flu can lead to death.

Children who have other health conditions that affect breathing, such as asthma, are at greater risk for flu complications. Their asthma or other lung condition can also be triggered by the flu.

Children with the flu are also more likely to develop ear infections.

How can I help prevent the flu in my child?

The best way to prevent the flu is to have the yearly flu vaccine. Each year, a new flu vaccine is available before the flu season starts. Flu shots and nasal spray are available. Talk with your healthcare provider if you have questions about how vaccines work and how well they prevent flu.

The flu vaccine is most often given as a shot into the muscle. For babies and young children, it's given as a shot in the thigh muscle. In older children, it's given as a shot in the upper arm muscle. It's also available as a nasal spray for healthy children over the age of 2, including teens who are not pregnant. Check with your child’s healthcare provider to see which is the best choice for your child.

The first time a child between the ages of 6 months and 8 years gets a flu vaccine, they will need a second flu vaccine 1 month later. This is to build up protection against the flu. Get your child’s first dose as soon as the vaccine is available. This allows the second dose to be given by the end of October. This will give your child the best protection for the flu season. After the first flu season, your child will need only 1 dose.

The vaccine is advised for all children 6 months and older. But for some children, it’s more critical for them to get a flu shot because they are more likely to have complications from the flu. The flu shot should be given to any child who has any of these:

• A long-term heart or lung condition

• An endocrine disorder such as diabetes

• A kidney or liver disorder

• Weak immune system from HIV/AIDS or long-term use of steroids or other immune-suppressing medicines

• A blood disorder such as sickle cell disease

A flu shot should also be given to: 

• A child who has a family member with a long-term (chronic) health condition

• A child or teen taking aspirin as long-term therapy

• A child with parents or caregivers at high risk for complications from the flu

Some side effects of the vaccine can seem like mild flu symptoms. But the vaccine doesn't cause the flu. Side effects can be prevented by taking over-the-counter medicines such as acetaminophen. Never give your child aspirin without talking with your child's healthcare provider first. Possible side effects of the flu vaccine include:            

• Soreness in the arm where the shot was given

• Short-term symptoms such as mild headache or a low-grade fever for about 1 day after the shot

In addition to the flu vaccine, you can do other things to help reduce your child’s risk of getting the flu. You can also:

• Limit your child’s contact with infected people, if possible.

• Have your child wash their hands often

• Have your child wear a medical mask when in contact with many others or in large groups of people

And you can help prevent your child spreading the flu to others if you:

• Have your child cover their nose and mouth when coughing or sneezing. Teach them to use a tissue or cough or sneeze in the crook of their arm.

• Wash your hands before and after caring for your child.

• Clean surfaces in the home that others may touch.

When should I call my child's healthcare provider?

Call the healthcare provider if your child has:

• Symptoms that don’t get better, or get worse

• New symptoms

Key points about the flu in children

• Influenza (flu) is a very contagious viral infection of the respiratory system.

• It causes a high fever, body aches, a cough, and other symptoms.

• Most children are ill with the flu for less than a week. But some children have a more serious illness and may need to be treated in the hospital. The flu may also lead to lung infection (pneumonia) or death.

• The flu may be treated with acetaminophen, cough medicine, and antiviral medicine. Your child will also need lots of rest and plenty of fluids.

• The best way to prevent the flu is to have the yearly flu vaccine. The vaccine is advised for all children 6 months and older.

• Getting a flu vaccine is important to protect yourself and the people around you from the flu.

Next steps

Tips to help you get the most from a visit to your child’s healthcare provider:

• Know the reason for the visit and what you want to happen.

• Before your visit, write down questions you want answered.

• At the visit, write down the name of a new diagnosis, and any new medicines, treatments, or tests. Also write down any new instructions your provider gives you for your child.

• Know why a new medicine or treatment is prescribed and how it will help your child. Also know what the side effects are.

• Ask if your child’s condition can be treated in other ways.

• Know why a test or procedure is recommended and what the results could mean.

• Know what to expect if your child does not take the medicine or have the test or procedure.

• If your child has a follow-up appointment, write down the date, time, and purpose for that visit.

• Know how you can contact your child’s provider after office hours, and on weekends and holidays. This is important if your child becomes ill and you have questions or need advice.