Overview illustration of the Flu

Flu Overview

Influenza poses a significant burden to society, sickening millions of people every year. But getting an annual flu shot remains the best way to lower your risk of falling ill and possibly developing serious complications.

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You know what cooler weather means: the start of flu season! This highly contagious viral infection can cause symptoms like fever, congestion, sore throat, and body aches. Occasionally, it can also lead to life-threatening complications. There's no cure for the flu, but getting a flu shot every year can lower your risk of getting sick.

What is it?

From October to May, we're all at heightened risk of catching the flu, aka an influenza virus. These cooler winter months are prime time for them to circulate. Anyone, no matter how healthy, can catch the flu. If you're infected, your symptoms can come on without warning. General signs like chills, fever, and a runny nose usually run their course within a week, while other symptoms—like extreme fatigue— may take up to two weeks to go away.

Most people recover from the flu, but in some cases, it can cause severe complications, worsen health conditions you already have, or be fatal. The 1918 flu pandemic took more lives than any other disease outbreak in history—some experts estimate the global death toll was between 50 and 100 million people.

Like all viruses, influenza viruses need new hosts to survive. Because of that, they're constantly changing in an effort to evade immunity and continue to spread.


Although we all say we're sick with "the" flu, it's more accurate to say that you're sick with a strain of the flu virus. Over 60 strains have already been identified.

There are actually four types of influenza viruses—A, B, C, and D—but only strains from the A and B types cause annual flu outbreaks.

Influenza A: Two strains of this type (H1N1 and H3N2) are known to affect people, and are always included in the annual flu vaccine. Influenza A viruses are the ones that have been responsible for global flu pandemics.

Influenza B: Although this type of influenza is less likely to make you severely ill, one strain of it is always chosen to be included in the flu vaccine.

Influenza C: If you're infected with an influenza C virus, you may have only mild symptoms or no symptoms at all. This category of viruses is also less common than A and B types.

Influenza D: Type D strains only affect cattle, not people.


While colds come on gradually, the flu can hit without much warning.

Once you're infected, you could experience:

Some people also have vomiting or diarrhea, although these are more likely to happen in children. Less common—but more serious—flu symptoms include:

If you have any of these symptoms, or a chronic health issue worsens while you have the flu, it's important to see your doctor right away.


The flu spreads through tiny respiratory droplets that escape someone's mouth or nose when they sneeze, cough, talk, or laugh. If a droplet ends up in your nose or mouth, you can become infected.

Most people who have the flu can infect others the day before they develop any symptoms. (And not everyone will show outward signs of being sick.) This infectious period continues up to a week after your symptoms begin. Children and people with weak immune systems can be contagious for even longer.

The flu virus can live on some surfaces for up to 48 hours, so if you come into contact with it, then touch your fingers to your eyes, nose, or mouth, you could get sick. Still, this isn't how most people catch the flu.


If there's a flu outbreak where you live, your doctor may only need to examine you and hear about your symptoms before diagnosing you. They can also order a test to confirm you're sick with a strain of the flu. Two of the most common tests include:

Rapid Influenza Diagnostic Test (RIDT): This test looks for parts of the flu virus in mucus from your nose or throat. You get results in 10-15 minutes, but RIDTs aren't highly accurate.

Rapid Molecular Assay: Although this test takes slightly longer than an RIDT, the results are more precise. It also relies on a swab from your nose or throat, and checks for genetic material from the virus.

Other lab tests can also check for influenza, but the results can take longer.


Most people don't need medical treatment for the flu—your immune system should be able to fight off the influenza virus without help.

If you have a mild case, staying home so you can take care of yourself and not infect others is a good idea. Get lots of rest, stay hydrated, and use over-the-counter products to relieve some of your symptoms.

Some people who get the flu can have complications like bronchitis, pneumonia, ear and sinus infections, and even inflammation of your heart or brain. You're at higher risk of this happening if:

  • You're pregnant
  • You're over the age of 65
  • You have a chronic health condition like asthma, diabetes, heart disease
  • You're Native American or Alaska Native
  • Children under the age of 5 are also at higher risk of these serious issues.

If you're in a high-risk group or your flu symptoms are severe, check in with your doctor. Different antiviral drugs like Tamiflu (oseltamivir) and Zanamivir (Relenza) can be used to shorten the length of your infection. Timing is important — these medications are most effective when they're started within 48 hours of your onset of symptoms.

Antiviral drugs can't prevent complications from the flu. If you start feeling worse, see your doctor right away. Other medications may be necessary.


Your best bet for preventing the flu? Get the flu vaccine—every year.

At the start of the year, experts look at data from different countries to figure out which three A and B influenza strains are the most common. This info's used to build the seasonal flu vaccine that comes out in the fall, either as a shot or a nasal spray.

The flu vaccine isn't perfect—you can still catch a different strain of influenza that wasn't included. Still, it's worth getting. Every shot you get bolsters your immunity to a few different flu strains.

To stay healthy, you can also:

  • Keep your distance. Stay socially distanced from anyone who has flu-like symptoms.
  • Frequently wash your hands. Use hand sanitizer if soap and water aren't available.
  • Try not to touch your face. You don't want germs on your fingers to get into your nose or mouth.
  • Take good care of yourself. You've heard it before but it bears repeating—getting enough sleep, eating healthy foods, managing stress, and finding time to be active can all help shore up your immune system.

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