All About the Flu (Influenza)

What Is the Flu?

The flu is an infection of the respiratory tract (nose, throat, and lungs). It's caused by a virus that spreads easily from person to person. Flu viruses usually cause the most illness during the colder months of the year. In the United States, flu season is from October to May.

Top Things To Know

• Prevention is key: Protect children from the flu with the flu vaccination which all children 6 months and older can get. Also, teach children to wash their hands frequently and avoid close contact with those who are sick. 
• The flu can be severe in kids: Children under 5, especially those under 2, are at higher risk for flu complications, like pneumonia, dehydration, and hospitalization. The flu could also make underlying medical conditions like asthma worse. 
• Symptoms include: Kids with the flu may have a fever, cough, sore throat, runny or stuffy nose, muscle or body aches, headaches, chills, fatigue, vomiting, and diarrhea.

What Are the Signs & Symptoms of the Flu?

When people have the flu, they usually feel worse than they do with a cold. Most people start to feel sick about 2 days after they come in contact with the flu virus. They might have:

• a fever that comes on suddenly
• chills
• headache
• muscle aches
• dizziness
• loss of appetite
• tiredness
• a cough
• sore throat
• runny nose
• nausea or vomiting
• weakness
• ear pain
• diarrhea

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

What Problems Can Flu Cause?

Some people are more likely to have problems when they get the flu, including:

• kids up to age 5, especially those under 2 years
• people with a weak immune system from medicines (such as chemotherapy or long-term steroid use) or illnesses (like HIV infection or cancer)
• people with chronic (long-term) medical conditions, such as asthma or diabetes
• kids or teens who take aspirin regularly
• people who are overweight
• women who are pregnant or just had a baby
• people who live in long-term care facilities, such as nursing homes
• people 65 years and older

If they get the flu, their illness can be more serious. They can develop pneumonia or get additional infections (like bacterial infections). If this happens, many will need medical care in the hospital. So it's important for them not to be near anyone who has the flu or flu-like symptoms.

People who have flu symptoms should keep their distance from anyone who might get very sick if they catch the flu.

When Should I Call the Doctor?

Call the doctor if your child has:

• a fever and is 3 months of age or younger
• a fever that lasts for 5 or more days
• a bad cough
• symptoms that get worse 
• a stiff neck
• a headache that doesn't go away after taking acetaminophen or ibuprofen
• a long-term medical condition and has flu symptoms

Get medical help right away if your child has trouble breathing.

What Causes the Flu?

The flu gets its name from the virus that causes it — the influenza virus. It spreads when people cough or sneeze out droplets that have the virus and other people breathe them in. The droplets also can land on things like doorknobs or shopping carts, infecting people who touch them.

Is the Flu Contagious?

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

The flu usually happens in annual epidemics. An epidemic is when an illness spreads quickly and infects lots of people in an area at the same time. Some years the epidemic is more severe and widespread than others. An epidemic that spreads worldwide is called a pandemic. This is far less common.

How Is the Flu Diagnosed?

Kids who have the flu usually look ill and miserable. Many don’t need an official diagnosis, since viral infections are often treated in the same way.

But if health care providers want to be sure that someone has influenza, they might do a test. They'll take a sample of mucus by wiping a long cotton swab inside the nose or throat. Results might be ready quickly, or can take longer if the test is sent to a lab.

How Is the Flu Treated?

Most kids with flu get better at home. Make sure your child:

• drinks lots of liquids to prevent dehydration
• gets plenty of sleep and takes it easy
• takes acetaminophen or ibuprofen to relieve fever and aches (Don't give kids or teens aspirin because of its link to Reye syndrome.)
• wears layers that are easy to remove (Kids might feel cold one minute and hot the next.)
• uses a cool-mist humidifier to help with congestion
• tries a teaspoon of honey (for children over 1 year old) to help with cough
• uses a mentholated vapor rub on the chest (for children over 2 years old) according to the directions on the package

Children with the flu should stay home from school and childcare until they feel better. They should go back only when they haven't had a fever for at least 24 hours without using a fever-reducing medicine. Some kids need to stay home longer. Ask the doctor what's best for your child.

Doctors may prescribe antiviral medicine for a very ill child or kids who are at risk for more serious symptoms. The medicine can shorten the flu by 1–2 days. It works best if children start taking it within 48 hours of the start of the flu. If a doctor prescribes antiviral medicine for your child, ask about any possible side effects. Doctors won't prescribe antibiotics for the flu. Antibiotics work only against bacteria, not viruses.

How Long Does the Flu Last?

Fever and other flu symptoms often go away after a week or so, but some people may still have a cough or feel weak for longer than that.

Can the Flu Be Prevented?

There's no guaranteed way to avoid the flu. But getting the flu vaccine every year can help. Everyone 6 months of age and older should get it each year.

It's best to get the flu vaccine before the end of October, as flu season starts. But even if you don't, you can get it later while the flu is still going around. Many health care providers give flu vaccines through May if the flu virus is still circulating.

Kids can get a flu vaccine at the same time they get other vaccines, like the COVID-19 or RSV shots. If your child is sick, has a fever, or is wheezing, talk to your doctor to see if you need to reschedule vaccines.

As with many germs, washing hands well and often and avoiding contact with sick people can help protect someone from getting sick.

What Else Can Help?

If someone in the family has the flu, they can help prevent spreading it by:

• never sharing cups and eating utensils.
  
• staying home from work or school until they're better
• covering their mouth and nose with a tissue when they cough or sneeze, then putting it in the trash
• coughing or sneezing into their upper arm, not their hands, if a tissue isn't handy

Other Common Questions

Is it a cold, the flu, RSV, or COVID-19?

All these illnesses are caused by viruses that infect the respiratory tract. All are contagious and can spread easily from person to person. And they cause some similar symptoms. So it can be hard to tell them apart.

Here are some things to look for if your child gets sick.

Would an antibiotic help my child feel better from the flu?

No. The flu is a virus and antibiotics only work on bacteria.