When you don’t feel well this time of year, figuring out the cause is important, because it will point you to you treatments that can make you feel better and even shorten the time you’re sick.

But figuring out what you have isn’t always easy.

That was the case for Amber Yahle of Springfield, VA. When she first got sick in January, she assumed it was a stomach bug and not the flu because she had gotten a flu shot in October. But her symptoms worsened so quickly, she ended up in urgent care the next day.

“I only had a mild fever the first day, but by the second day, I had the most extreme pain in my abdomen and I was coughing so badly, my ribs felt like they were cracking with each cough. I was literally holding a pillow to lean against each time I coughed because it hurt so much,” Yahle says.

She was diagnosed with influenza A — and says she was shocked.

“I thought for sure it was more like walking pneumonia or bronchitis,” she says. She was prescribed Tamiflu for 6 days, which she says helped a lot — and got her back on her feet in time to make a family vacation. “It made me feel so much better,” Yahle explains.

Flu diagnoses take some by surprise, and there are two different kinds you need to understand: influenza A and influenza B. Other people get diagnosed with “flu-like illness,” which can also be a confusing term.

Understanding the difference between these terms and your treatment options is important, with rates of these diagnoses high across much of the country. The CDC estimates that as of mid-January 2020, there had been nearly 10 million flu illnesses, 87,000 hospitalizations, and 4,800 deaths from flu — including 32 children — making this season one of the most deadly on record.

WebMD talked with some experts to break down the difference between the two diagnoses and what it means for you.

What is the difference between the flu and flu-like illness?

The flu is “a contagious respiratory illness caused by influenza viruses that infect the nose, throat, and sometimes the lungs,” according to the CDC, which says as many as 11% of Americans get it each season. It says symptoms include some or all of the following:

Cough and sore throat
Runny or stuffy nose
Muscle or body aches and chills
There are different strains of flu, including influenza A and B. In January 2020, the CDC warned an early season pediatric influenza B is circulating — something that hasn’t happened in 27 years. That strain is causing serious illnesses in the South in particular and is blamed for one death as of early January.

“Influenza-like illness” (ILI), also called “flu-like illness,” is a more wide-ranging category. The CDC says that with ILI, you have a fever of at least 100 F and a cough or sore throat, but the cause of the symptoms isn’t known.

How can doctors tell if you have flu or flu-like illness?

The flu is diagnosed from a swab test of your nose or throat. Flu-like illness is a clinical diagnosis, meaning it doesn’t involve an official test. A doctor simply decides by examining you.