It’s the height of flu season but not all symptoms of the flu virus point to influenza. Sudden fever and headache also may be symptoms of early meningitis, which often mimics the flu.

“Meningitis is a syndrome that refers to inflammation in the area that surrounds the brain,” says Mayo Clinic infectious diseases specialist Dr. Pritish Tosh.

He says many things can cause meningitis, including viruses, bacteria, fungi and parasites.

“There are different kinds of meningitis. Some are not infectious at all. Bacterial meningitis, which is what I think most people are concerned about, can be life-threatening, and if someone has a headache and fever, that very well could be bacterial meningitis.”

Seek immediate medical care if you or someone in your family has meningitis symptoms: Fever, severe, unrelenting headache, confusion, vomiting, stiff neck.