First: There’s no such thing as the stomach flu.

“‘Flu’ was simply short for ‘influenza’ and so the noro virus of course has nothing to do with influenza,” said Dr. David Zich, an emergency room doc at Northwestern Memorial Hospital.

“It is a misnomer.”

So, now that we’ve gotten that out of the way, what’s the difference between the flu and the norovirus?

Flu is respiratory. Norovirus is gastrointestinal.

Fever, nausea, coughing, and muscle aches: Flu.

Vomiting and diarrhea: Norovirus.

Zich said he saw cases of the flu peak a couple weeks ago.

“But in the last week, influenza has dropped off significantly, and for every one case of influenza I’m seeing about five cases of norovirus,” he said.

Zich said that since these two sicknesses are both viruses, there isn’t a simple antibiotic regimen that can make you feel better— in general, you just have to tough it out.

But, Zich said, if you’re got the norovirus and you vomit for more than 24 hours, or you’ve got the flu and a fever over 104, you should visit a doctor.

And at least now you know not to misdiagnose yourself.