The Flu: Symptoms, Treatment and Prevention Explained

The flu might seem like a mild health nuisance you may have to suffer through once or twice a year. And for many people, that is indeed the case.

It's important to know, however, that as many as 100,000 Americans die from influenza, according to recent estimates from the Centers for Disease Control and Prevention (CDC). The flu also causes up to 75 million illnesses and more than half a million hospitalizations.¹

This amounts to thousands of hours of lost productivity. Plus, getting sick with the flu is an unpleasant experience, even when symptoms are relatively mild.

Fortunately, you can take steps to protect yourself, your family and your community from experiencing the effects of influenza. This starts with understanding what the flu is, how to identify its symptoms, how to treat it and how to prevent it.

What Is the Flu?

What we call the flu is medically termed “influenza.” It is caused by one of the four influenza viruses:²

Each influenza virus wears a distinctive protein coat. Influenza A and B viruses change their coats (mutate) regularly, which is why you can get infected with influenza over and over again. Each time the influenza virus changes its coat, it becomes a new strain of the virus.

Your immune system actively watches for virus strains it has previously encountered, usually detecting them early and neutralizing them before you develop symptoms. However, when the influenza virus mutates into a new strain, it looks like a new virus to your immune system and can briefly circulate undetected. When your immune system finally discovers it and ramps up to neutralize it, you develop the characteristic flu symptoms.

When Is Flu Season?

Generally, the influenza A and B viruses mutate at least annually — before the start of flu season, which the CDC defines as October through May.³

You may be surprised to learn you can get the flu at any time of the year in the United States. It’s possible to get sick with the flu in the middle of July because the influenza viruses circulate year-round. However, influenza infections tend to begin surging at the start of the official flu season, and flu cases generally peak between December and February.³

What Is the Difference Between the Flu, a Cold and COVID-19?

Although the flu, a common cold and COVID-19 are all considered respiratory illnesses and have certain symptoms in common, they are caused by different viruses. As mentioned, the flu is caused by influenza viruses. The common cold is primarily caused by rhinovirus.⁴ And COVID-19 is caused by the SARS-CoV-2 virus.⁵

In general, you can tell the difference between the flu, a cold and COVID-19 by evaluating these characteristics:

You don’t need to try to distinguish between these illnesses yourself. If you develop a respiratory illness, you should see a healthcare professional for a diagnosis so you can receive appropriate treatment and avoid potential hospitalization.

Because influenza and COVID-19 cause very similar symptoms, you should get a medical diagnosis as early as possible when displaying any characteristics of either illness because these two infections require different treatment plans.

Symptoms of the Flu

Influenza symptoms generally develop rapidly after exposure to the virus and can include:⁶

• Fever

• Chills

• Body (muscle) aches

• Fatigue or tiredness

• Cough

• Sore throat

• Stuffy or runny nose

• Headache

You may not develop all of these symptoms if you have the flu — you may experience only a few of them. Some people also have reported dizziness while sick with the flu.⁷ Others notice an increased heart rate.⁸ Either of these symptoms could be a result of dehydration, so be sure to drink plenty of fluids if you’re sick with the flu.⁸

Note that influenza is a respiratory virus that does not affect the gastrointestinal tract. Sometimes people refer to having “stomach flu” when they’re experiencing cramps and diarrhea, but these symptoms are not caused by an influenza virus (except occasionally in children). Stomach flu generally refers to an illness called gastroenteritis.⁶

What Causes the Flu?

As stated above, the flu is caused by the influenza virus. But how do you pick up that virus?

Influenza viruses pass from person to person through microscopic droplets. Whenever we talk, sneeze, laugh or cough, we emit tiny droplets. If we are infected with the influenza virus and another person comes in contact with these droplets, they can inhale or otherwise ingest them and get infected, too.⁹

It may be possible, but less likely, to pick up the influenza virus from contaminated surfaces.⁹ For instance, if you touch a countertop covered with droplets containing influenza virus and then touch your nose or eyes, you might transfer the virus to yourself.

Healthy adults with robust immune systems are less likely to become infected with influenza, and if they do become infected their symptoms may be milder.

Some groups face a higher chance of getting the flu and experiencing serious complications, including:¹⁰

• Older adults over age 65

• Children under age 2

• Pregnant people up to two weeks postpartum

• Adults with chronic conditions like asthma and diabetes

• Adults and children with an autoimmune disorder

• People with a body mass index (BMI) above 40

• People who live in nursing homes

How the Flu Is Diagnosed

As soon as you develop respiratory symptoms, you should consider seeing a healthcare professional for a diagnosis. Your provider generally will diagnose influenza using one of two common tests:¹¹

• Rapid influenza diagnostic tests (RIDTs). These fast tests generally are accurate when reporting a positive result but produce a higher rate of false-negative results than other tests.

• Rapid molecular assays. These are slightly less fast than RIDTs but more accurate for both positive and negative results.

The tests require a mucus sample, which providers commonly obtain by inserting a swab into the nasal passages. They can test the swab’s contents right in the clinic and diagnose flu within 20 minutes.¹¹

Best Flu Treatments

Getting sick with the flu can be a miserable experience that can make you feel feverish, achy and very fatigued. You can expect flu symptoms to last from three days to two weeks.¹²

Fortunately, you can treat your flu symptoms in a variety of ways to help yourself feel better:

• Antiviral medications. Available by prescription, antiviral medications (not to be confused with antibiotics, which are a different class of drug) are an especially important treatment for anyone facing a high chance of developing flu complications. These medications are available as pills, liquids and inhalable powder.¹³

• Over-the-counter (OTC) medications. Decongestants, fever reducers, expectorants and other OTC preparations can reduce the severity of flu symptoms. However, anyone with a chronic health condition should use caution when choosing over-the-counter cold and flu medications, as they can cause elevated blood pressure and other side effects. Check with your healthcare provider or pharmacist to make sure a particular medication is safe for you to take.

• Hydration. Consuming plenty of fluids is essential for helping your body recover from the flu. Avoid caffeinated beverages, as they can be dehydrating. Focus on drinking plenty of plain water and, if possible, eating fluid-rich foods like melons, berries and cucumbers, as these also can help you hydrate while ill.

• Cool compresses. When feverish, applying a cool compress to the forehead or back of the neck feels good.

• Herbal teas. Natural remedies like herbal tea may contain chamomile, elderberry, ginger, honey and other compounds that can ease flu symptoms. Drinking warm, caffeine-free liquids also contributes to hydration.

• Warm bath or shower. Inhaling steam can ease respiratory symptoms and thin mucus, and the warm water can relieve muscle aches.

• Rest. Staying in bed or spending the day in a recliner allows your immune system to do its job of eliminating the virus. Do not go to work or out in public when you’re infected with influenza, as this can spread the virus to others.

• Humidification. Cool, moist air in the environment (especially your bedroom) may soothe irritated respiratory passages and help you breathe better.

Some people wonder if a corticosteroid like prednisone can be used to treat flu. While a healthcare provider may prescribe a strong medication like this to people who are hospitalized with flu, steroids are not considered a frontline treatment for the average adult.¹⁴

How to Prevent the Flu

Nobody enjoys getting sick, and fortunately, you can take steps to avoid getting the flu. Try the following:¹⁵

• Getting vaccinated. Getting the flu shot once a year is the best way to prevent influenza infection. If you get infected anyway, being vaccinated reduces the severity of symptoms.

• Washing your hands. Good hand hygiene can prevent the spread of the influenza virus. If you happen to pick up the virus on your fingers, washing your hands thoroughly with soap and warm water and then drying thoroughly can remove the virus before you touch your eyes, nose or mouth and transfer the virus to yourself.

• Avoiding contact with people who are ill. If one of your coworkers is sick, keep a safe distance from them. Avoid crowded public areas during flu season.

How Does the Flu Vaccine Work?

When you get a flu shot, your body receives a fragment of an influenza virus. The nasal spray vaccine delivers a weakened version of the live virus. Receiving a dose of either vaccine allows your immune system to generate antibodies to recognize and neutralize the virus should you become infected.¹⁶

You can get a flu shot at almost any pharmacy and many healthcare providers’ offices. Almost all health insurance policies cover the flu shot as preventive care, which means you shouldn’t have to pay to receive this important vaccine.¹⁷

Why you should get a flu shot

The CDC recommends that everyone over the age of 6 months should get a flu shot.¹⁶ Only a tiny subset of people should avoid the flu vaccine — it is safe and effective for most people.¹⁶ If you have questions about this, ask your healthcare provider.

Some people do not believe the flu shot works. This is untrue. The effectiveness of the flu vaccine does vary each year because its effectiveness is based on how well the vaccine matches the strain of viruses currently circulating.¹⁶ But it historically has been up to 60% effective at lowering the likelihood of a flu-related doctor visit; in children, the vaccine reduces the chance of life-threatening flu complications by about 75%.¹⁸

The benefits of getting vaccinated against the flu include:¹⁸

• Reduced symptom severity if you do get sick from flu after vaccination

• Reduced likelihood of hospitalization from influenza

• Reduced rates of some cardiac events in people with chronic heart disease

• Reduced likelihood of hospitalization in people with chronic lung diseases and diabetes

• Protecting unborn children from getting influenza during their first months of life when pregnant people get vaccinated

• Potentially protecting vulnerable people in your community by reducing the spread of the influenza virus

Side effects of getting a flu shot

As you know, receiving an injection can be moderately painful. This is the most common side effect of the flu vaccination. The injection site also may develop redness, heat and minor swelling.¹⁶

The flu vaccine can also occasionally cause fever, especially in children. This is normal and doesn’t mean the shot or nasal spray gave you the flu. In fact, it’s not possible for a vaccine to give you the flu.¹⁶

When It Comes to the Flu, Knowledge Is Power

Getting the facts about the flu is your first step in preventing and treating the illness. When you understand how the flu is transmitted, how to prevent it and how to treat it, you can better protect your own health and that of your children, other loved ones and the community. If you have questions about influenza or whether the vaccine is safe for you and your family, ask your healthcare provider. Plan to have a safe, healthy flu season this year.

Frequently Asked Questions About the Flu

Do you still have questions about the flu? Here are answers to some frequently asked questions.

Managing Health and Wellness Costs With the CareCredit Credit Card

If you are looking for an option to help manage your health and wellness costs, consider financing with the CareCredit credit card. The CareCredit credit card can help you pay for the care you want and need and make payments easy to manage.* Use our Acceptance Locator to find a provider near you that accepts CareCredit. Continue your wellness journey by downloading the CareCredit Mobile App to manage your account, find a provider on the go and easily access the Well U blog for more great articles, podcasts and videos.

Your CareCredit credit card can be used in so many ways within the CareCredit network including vision, dentistry, cosmetic, pet care, hearing, health systems, dermatology, pharmacy purchases and spa treatments. How will you invest in your health and wellness next?

Author Bio

Elizabeth Hanes, R.N., has substantial clinical experience and diverse expertise including critical care, plastic and reconstructive surgery, heart health, nutrition and senior health. For over 20 years, she has blended her clinical background with writing for leading healthcare publications, such as WebMD, Anthem, Healthgrades and Modern Healthcare, among others. She is committed to creating exceptional healthcare content that informs and educates both patients and health professionals.