Do you have the flu? 17 things to know about flu symptoms, flu shot side effects and more

Ohio has reported the third flu-related infant death this season.

Health officials across the country have started reporting deaths attributable to flu, prompting experts to amp up the warnings.

» RELATED: What to know about the 2018-2019 flu season

"An annual flu vaccine is the best way to protect against influenza and its potentially serious complications," according to the Atlanta-based Centers for Disease Control and Prevention.

Last year, a flu outbreak swept the United States and killed nearly 80,000 Americans, including 180 children, 80 percent of whom were not vaccinated against the deadly strain.

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In Georgia, five children died and hundreds were hospitalized amid the state’s worst flu season on record.

As of Oct. 20 this year, the state department has recorded five hospitalizations due to flu and zero deaths.

Since 2010, the CDC estimates the flu has resulted in between 9.2 million and 35.6 million illnesses.

Health experts continue to urge folks to get their flu vaccines. Even if the vaccine isn’t a perfect match, it can still help lessen the severity of the flu and reduce the potential for complications.

» RELATED: 8 self-care strategies to get you through your flu symptoms

Here’s what you should know about the flu, flu shot and more from experts in the field:

What exactly is flu?

According to the CDC, the flu is "a contagious respiratory illness caused by influenza viruses."

Influenza viruses directly infect the nose, throat and lungs. It can cause mild to severe illness and can even be fatal.

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How does the influenza virus start?

Influenza actually originates among birds and other animals in Southeast Asia, then spreads to Europe and, lastly, the U.S., William Schaffner, chair of Vanderbilt Medical School's department of preventative medicine, told ABC News.

» RELATED: How does flu kill healthy people?

How does the virus spread among humans?

Humans spread the virus we have in our throats to others when we touch each other, especially noses and mouths, Schaffner said.

» RELATED: 11 things parents need to know about the flu, the vaccine, how long kids need to stay out of school 

Why are we so susceptible to the virus?

It’s because the virus comes in different forms (and several forms) every year, according to Schaffner.

» RELATED: Family warns of dangers after 21-year-old dies of flu complications

When exactly is flu season?

Peak month of flu activity (1982-2016)

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Flu viruses are most common during the fall and winter, though season flu viruses can be found year-round in the U.S.

According to the CDC, virus activity often increases in October and peaks between December and February. It can last through May.

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What are the symptoms of flu?

Someone who is exposed to the flu virus may begin to experience the following symptoms about one to four days after exposure.

From the CDC:

  • Fever* or feeling feverish/chills (Note: Not everyone will experience a fever)
  • Cough
  • Sore throat
  • Runny or stuffy nose
  • Muscle or body aches
  • Headaches
  • Fatigue (very tired)
  • Some may experience vomiting and diarrhea, though this is more common in children than adults.

How long is someone contagious after contracting the flu?

An infected person may be able to infect other people and spread the illness one day before they even begin to experience symptoms.

According to the CDC, the period of contagiousness can continue between 5-7 days after becoming ill.

The period of contagiousness could last even longer for those with weakened immune systems, especially young children.

Who is most at risk of getting the flu?

According to the World Health Organization, pregnant women, older people, young children and people with certain chronic health conditions (asthma, diabetes, heart disease) are most at risk.

What does the flu vaccine do?

The seasonal vaccine protects against the form of the virus scientists are predicting will be most comon during the upcoming flu season.

According to CDC experts, the traditional three-component flu vaccine protects against three flu viruses: H1N1, H3N2 (both influenza A viruses) and an influenza B virus.

The quadrivalent flu vaccine protects against all three plus an additional influenza B virus.

So far this season, "influenza A H1N1 viruses have been the most commonly identified flu viruses," the CDC reported in October.

Who should get a flu shot?

CDC experts recommend everyone 6 months or older receive a flu shot every year.

What about the nasal spray flu vaccine?

The CDC does not recommend the nasal spray flu vaccine during the 2017-2018 flu season. Injectable influenza vaccines are recommended instead.

Can people with egg allergies receive the flu shot?

Yes. CDC experts recommend those with severe egg allergies be vaccinated in a medical setting with a health care provider.

Should pregnant women receive the flu vaccine?

Yes. Experts recommend pregnant women get the shot during any trimester of their pregnancy to protect both themselves and their babies.

Will you get the flu from the flu shot?

No, the vaccine does not cause flu. (CDC)

What are the side effects of a flu shot?

Common mild side effects may include soreness or swelling, headaches, nausea, muscle aches and fever.

The injection can occasionally cause fainting, just like other injections.

When is the best time to get the flu shot?

It takes about two weeks after getting the shot for the vaccine to protect against influenza.

That’s why the CDC recommends people get vaccinated by the end of October, before the flu season starts to get bad.

However, if October has passed, it is still beneficial to get vaccinated, even into January or later.

How much does a flu shot cost and where can I get one?

Under the Affordable Care Act, most people with insurance who go to a health care provider covered by their plan should receive the flu vaccine for free.

But pharmacy chains, universities and other corporations have also started offering the vaccines either for free or at low costs.

Use the CDC’s Flu Vaccine Finder below to find a clinic near you. Just enter your ZIP code and hit “Go.”

Learn more about the flu at