What is the flu? 17 things to know about flu symptoms, flu shot side effects and more

5:19 p.m Thursday, Oct. 12, 2017 Atlanta health, diet and fitness news

According to the Centers for Disease Control and Prevention, the United States experiences flu epidemics every year. 

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

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

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.

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.

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

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

Peak month of flu activity (1982-2016)

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.

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

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.

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.

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.

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

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

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

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

No, the vaccine cannot cause flu. (CDC)

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.

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.

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.

Learn more about the flu at CDC.gov.

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