What Is the Flu (Influenza)?

Banner Health wants to help protect you and your family from influenza (the flu). Here is the latest information on the flu, so you can keep yourself and your loved ones healthy this flu season.

What is the flu?

The flu is a contagious respiratory (breathing) illness caused by the influenza virus. It affects the nose, throat, airways and sometimes the lungs.

The flu can range from mild to severe. In some cases, it can lead to serious complications – especially in high-risk individuals.

Are there different types of flu viruses?

There are several strains of the flu virus, including influenza A, B and C. Some strains can also have different subtypes, which makes the flu virus very complex.

Different flu viruses circle the globe each year, which is why it is important to protect yourself and your loved ones by getting a flu shot every year.

Influenza A viruses are the most common and can potentially cause more severe illness. Influenza B viruses are less common but still cause significant illness. These strains aren’t broken down into subtypes but can change over time.

Influenza A and B strains are responsible for seasonal flu outbreaks. Most people catch the flu in the winter, especially between December and February in the United States.

Influenza C viruses cause milder respiratory symptoms. They aren’t seasonal, so the number of cases doesn’t change throughout the year.

What is the difference between the flu and the common cold?

The flu and the common cold are both types of upper respiratory infections, but they are not the same.

• Colds usually come on over the course of a few days, but the flu comes on suddenly and lasts longer.
• Cold symptoms are usually mild and last one to two weeks. Flu symptoms, however, are much worse than a cold.
• Colds can happen any time of the year, but the flu usually happens during late fall and winter.

What are the symptoms of the flu?

Flu symptoms often appear suddenly and may include the following:

• Fever (usually high)
• Cough
• Sore throat
• Runny or stuffy nose
• Muscle or body aches
• Fatigue (extreme tiredness)
• Headache
• Chills
• Nausea, vomiting or diarrhea (more common in children)

While the flu can cause stomach upset in children, it is not stomach flu. The stomach flu (medically known as viral gastroenteritis) can be caused by several viruses and only causes stomach problems (such as diarrhea and vomiting), not breathing problems.

Learn more about flu symptoms.

How does the flu spread?

The flu is very contagious and usually spreads through tiny droplets that are made when an infected person coughs, sneezes or talks. You can catch the flu by breathing in these droplets through your nose or mouth.

You can also become infected by touching surfaces (like door handles, counters, computers and phones) that have the virus on them and then touching your face – especially your mouth, nose or eyes.

Who is at the most significant risk for complications from the flu?

Certain people are at higher risk of getting severe complications from the flu. These groups include:

• Children younger than 5 years old
• Adults older than 65
• Pregnant people
• People with chronic medical conditions, such as asthma, diabetes or heart or vascular disease
• People with weakened immune systems, such as those living with HIV/AIDS or cancer
• People with a BMI (body mass index) greater than 40

People in these high-risk groups must take extra care not to catch the flu, get their flu shot every year and see a health care provider for any flu-related symptoms.

Learn more about your risk of experiencing severe complications.

Prevention, diagnosis and treatment

Vaccination: Your best defense

Getting a flu shot every year is the most effective way to prevent the flu and stay healthy. The flu vaccine helps your immune system protect against that year’s most widespread flu strains, so you must get a flu shot every year. Best of all, even if you get sick with a different type of flu than the one in the shot, vaccination lowers your risk of getting very sick.

The vaccine is especially important for high-risk individuals, including young children, older adults, pregnant people and those with chronic medical conditions and/or weakened immune systems.

Learn other ways to reduce your risk of getting the flu.

When should I seek treatment?

Most people with the flu recover within a week or two by getting plenty of rest, drinking lots of clear fluids and taking over-the-counter (OTC) medicines to help with symptoms. However, certain high-risk individuals should see a health care provider if they catch the flu.

Seek immediate care if you or a loved one experiences the following:

• Difficulty breathing or shortness of breath
• Chest pain or severe stomach pain
• Persistent vomiting
• Dizziness or confusion
• Symptoms that get better, then come back with higher fever and/or cough

If you experience these symptoms, it’s very important to contact your health care provider. Learn when to seek medical care versus emergency care for the flu.

How is the flu diagnosed?

Health care providers can diagnose the flu based on your symptoms, a physical exam and/or additional tests.

Rapid influenza diagnostic tests (RIDTs) can provide results within minutes, although they may not always be correct. Sometimes, your provider may recommend a more accurate test, such as a viral culture or a polymerase chain reaction (PCR) test.

Learn more about diagnosing the flu.

How is the flu treated?

Many people can manage symptoms at home by getting plenty of rest, drinking lots of clear fluids and taking OTC medicines to lower your fever or help with congestion.

Antiviral medications can help treat the flu and reduce symptoms if taken within the first 48 hours (about two days) of when symptoms start. These prescription medications can shorten how long you have the flu and help prevent complications, especially in high-risk individuals.

Learn more about flu treatment and if antiviral medicine might be right for you.