What is the Flu (Influenza)?

What is the flu?

Influenza, or the flu, is a contagious illness that affects your lungs, throat and nose. Symptoms can range from mild to severe. In some cases, the flu can lead to serious complications - especially for young children, older adults, and people with certain health conditions.

At Banner Health, we want to help you stay well by understanding how the flu spreads, what symptoms to watch for, and how to protect yourself and others.

What are the types of flu viruses?

There are three main types of influenza viruses that affect people:

• Influenza A – The most common type, often responsible for widespread outbreaks.
• Influenza B – Can also cause seasonal illness, especially in children.
• Influenza C – Typically causes mild symptoms and doesn’t lead to large outbreaks.

Flu season in the U.S. usually peaks between December and February, but it can begin as early as fall and last through spring.

Flu symptoms

Flu symptoms often come on quickly and can include:

• Fever or chills
• Cough
• Sore throat
• Runny or stuffy nose
• Headaches
• Muscle or body aches
• Fatigue or tiredness
• Vomiting or diarrhea (more common in children)

Even though people sometimes call it the “stomach flu,” the flu is a respiratory illness—not a stomach bug.

What’s the difference between the flu and a cold?

The flu tends to come on suddenly and feels more intense than a cold. You may experience high fever, body aches, and exhaustion that can last a week or more. Colds usually develop slowly and cause milder symptoms like a stuffy nose or sore throat.

How does the flu spread?

The flu spreads through tiny droplets when an infected person talks, coughs or sneezes. You can also catch the flu by touching surfaces that have the virus on them and then touching your eyes, nose or mouth.

People are most contagious during the first three to four days after symptoms begin, but some can spread the virus even before symptoms appear.

Who’s most at risk for flu complications?

While anyone can get the flu, some people are more likely to develop serious complications, including:

• Children under age 5
• Adults 65 and older
• Pregnant individuals
• People with chronic conditions like asthma, heart disease or diabetes
• People with weakened immune systems
• Individuals with a body mass index (BMI) over 40

If you're in one of these groups, it’s important to take extra precautions during flu season.

How is the flu diagnosed and treated?

If you think you have the flu, contact your health care provider. They may recommend a flu test, especially if you’re at higher risk for complications.

Treatment usually includes rest, fluids and over-the-counter medicines to reduce fever and pain. Prescription antiviral medications can help shorten the illness or make symptoms milder if started within the first two days.

How to prevent the flu

Here are some simple steps you can take to reduce your risk:

• Get a flu shot every year
• Wash your hands often
• Avoid close contact with people who are sick
• Stay home when you’re sick
• Cover your mouth and nose when coughing or sneezing

The annual flu vaccine is updated each year to help protect against the most common flu strains.

When should you see a doctor for the flu?

See a health care provider right away if you or a loved one has:

• Trouble breathing
• Chest pain
• Severe weakness or dizziness
• Confusion
• Symptoms that get better but then come back worse

These could be signs of complications that need medical attention. Learn when to seek medical care versus emergency care for the flu.

Protect yourself this flu season

You can get your flu shot during a visit to any Banner Urgent Care location. Walk in or save your spot online - no appointment required.

Find a Banner Urgent Care near you.