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The Flu (Influenza)

What Is the Flu?

Influenza, or "the flu," is a very contagious viral infection of the respiratory tract. In the United States, flu season runs from October to May, with most cases happening between late December and early March.

What Are the Signs & Symptoms of the Flu?

The flu is often confused with the common cold. But flu symptoms usually are more severe than the typical sneezing and stuffiness of a cold.

Symptoms usually begin about 2 days after exposure to the and can include:

Infants with the flu also may suddenly seem fussy or just "not look right."

It's important to treat the flu seriously because it can lead to pneumonia and other life-threatening complications, particularly in babies, senior citizens, and people with long-term health problems.

What Causes the Flu?

The flu is caused by the influenza virus. The virus spreads when infected droplets are coughed or sneezed into the air.

Is the Flu Contagious?

Yes, the flu is very contagious. People can spread the flu from a day before they feel sick until their symptoms are gone. This is about 1 week for adults, but can be longer for young kids.

The flu usually happens in small outbreaks. But epidemics — when the illness spreads quickly and affects many people in an area at the same time — tend to happen every few years. Epidemics often peak within 2 or 3 weeks after the first cases are reported.

When an epidemic spreads worldwide, it's called a pandemic.

Who Gets the Flu?

Anyone can get the flu, but kids tend to get it more often than adults. Some people are at higher risk of getting sicker when they have the flu, and sometimes need to be treated in a hospital. These include:

  • all kids up to the age of 5, but especially babies
  • anyone 65 years and older
  • all women who are pregnant, trying to become pregnant, have recently given birth, or are breastfeeding during flu season
  • anyone whose immune system is weakened from medicines or illnesses (like HIV infection)
  • residents of long-term care facilities, such as nursing homes
  • any adult or child with chronic medical conditions, such as asthma
  • kids or teens who take aspirin regularly and are at risk for developing Reye syndrome if they get the flu
  • caregivers or household contacts of anyone in a high-risk group (like children younger than 5 years old, especially those younger than 6 months, and those with high-risk conditions)

How Is the Flu Diagnosed?

When doctors suspect the flu, they might use a long cotton swab to get a sample from the back of the nose or throat. Testing this sample in a lab can determine if a child has the flu.

But usually this isn't necessary. Based on symptoms and how the child looks during the visit, a doctor can often tell if it's the flu, especially if the flu is going around.

Without testing, the doctor can't know for sure if it's the flu or another viral infection (like the common cold). But treatment plan is generally the same whether a child is tested or not.

How Is the Flu Treated?

The flu rarely needs specific medical treatment. But some kids may have a greater risk of complications from the flu, including:

  • kids with chronic medical conditions such as asthma, diabetes, or HIV infection
  • children under 2 years old

Some of these kids might need treatment in a hospital.

Doctors may prescribe antiviral medicine for a very ill child or one who is at higher risk for health problems from the flu. The medicine can shorten the illness by 1–2 days and prevent potential problems. It's only helpful if given within 48 hours of the start of the flu. If an antiviral medicine is prescribed, be sure to discuss any possible side effects with the doctor.

Most otherwise healthy kids can recover from the flu at home. They should:

  • drink lots of liquids to prevent dehydration
  • get plenty of sleep and take it easy
  • take acetaminophen or ibuprofen to relieve fever and aches. Do not give aspirin to children or teens because of its link to Reye syndrome.
  • wear layers, since the flu often makes them cold one minute and hot the next. Wearing layers — like a T-shirt, sweatshirt, and robe — makes it easy to add or remove clothes as needed.

Kids who are sick should stay home from school and childcare until they feel better and have been fever-free for at least 24 hours without the use of a fever-reducing medicine. Some might need to stay home longer, depending on how they feel. If you have questions or concerns, talk to your doctor.

How Long Does the Flu Last?

After 5 days, fever and other symptoms usually stop. But a cough and weakness may continue. All symptoms usually are gone within a week or two.

Can the Flu Be Prevented?

There's no guaranteed way to have complete protection from the flu. But these steps can make spreading the flu less likely:

  • Wash your hands well and often with soap, especially after using the bathroom, after coughing or sneezing, and before eating or preparing food.
  • Never pick up used tissues.
  • Don't share cups and eating utensils.
  • Stay home from work or school when you're sick with the flu.
  • Cover your mouth and nose with a tissue when you cough or sneeze, then put it in the trash. If a tissue isn't available, cough or sneeze into your upper arm, not into your hands.

What Else Should I Know?

Vaccination is a great prevention strategy. The annual flu vaccine is recommended for everyone 6 months of age and older. It's usually offered between September and mid-November.

People who got the vaccine one year aren't protected from getting the flu the next. That's because the protection wears off and flu viruses change. This is why the vaccine is updated each year to include the most current strains of the virus.

So to have the best protection against the flu, it's important to get the vaccine every year.

If your child is sick and has a fever, talk to your doctor about rescheduling the flu shot.

Date reviewed: September 2018