flu vaccine

Not everyone will get the flu this year, but everyone is at risk.

Flu-related events locally and nationally — a little boy's death in Delaware County over the weekend and the global coronavirus epidemic — have raised concerns about who's most at risk of complications from different strains of the flu.

There are actually four types of influenza viruses out there: A, B, C and D.

The most common is A, but this flu season began with a large number of influenza B cases, according to Dr. Ishminder Kaur, a physician at St. Christopher's Hospital for Children.

The difference between the two cannot be seen by the naked eye because both show similar symptoms, but they are both just as dangerous.

Here are some questions you might have about the flu and how to prevent it:

Who has the greatest risk of getting the flu?

Children under 18 are most likely to get sick from the flu, according to the Centers for Disease Control. Adults 65 and older are the least likely to catch the flu, but they are at higher risk for flu complications.

What are the four types of influenza?

Influenza A, B, C and D are the four different types of viruses and not all impact humans.

Both A and B are the common virus types seen each year, with B usually being less common. B infections typically come later in the flu-season, according to Kaur. This year is an exception to that and researchers are not sure why.

Influenza B also is exclusively transmitted between humans.

Influenza C generally causes mild illness and is not thought to cause human flu epidemics.

Influenza D is different from the rest. It is not known to affect humans. Instead, it causes illness in cattle.

Who has the highest risk for flu complications?

Children younger than five years old are at high risk of developing flu complications like pneumonia, dehydration and brain dysfunction.

"The most common complications of flu in kids that cause death are pneumonia and dehydration," Dr. Rob Danoff of Jefferson Health told NBC10. "So those are some of the concerns that we really want to watch out for."

Influenza is also especially serious for adults 65 and older because of their weaker immune systems. Pneumonia, bronchitis, sinus infections and ear infections are some of the flu-related complications that can occur.

Other people at high risk of flu complications are pregnant women and those with asthma, diabetes, HIV/AIDS or cancer. A full list of high risk populations can be found here.

When should someone with the flu go to the doctor?

Typically, you do not need to go to the doctor when you have the flu.

“Most people with the flu have mild illness and do not need medical care or antiviral drugs,” Dr. Scott Tomaine of Children's Hospital of Philadelphia said in a published report on the hospital's website.

You should stay home and avoid contact with other people until the fever symptom is resolved for at least 24 hours.

If the person with the flu is considered high risk, they should go to the doctor.

"Any child who is not feeling well because of influenza may benefit from treatment in the first two to three days," Dr. Kaur said. She recommends you reach out to your physician if your child is experiencing symptoms.

What can be done to prevent catching the flu?

The number one way to prevent catching the flu is to get a flu shot. The CDC says everyone 6 months of age and older should get a flu vaccine every season with rare exception.

Aside from the flu shot, here are some steps you can take to avoid spreading germs that lead to respiratory illnesses like the flu:

  • Avoid close contact with people who are sick
  • Stay home when you're sick
  • Cover your mouth and nose when coughing or sneezing
  • Wash your hands often
  • Avoid touching your eyes, nose and mouth
  • Clean and disinfect surfaces