U.S. federal health officials say the number of comfirmed fungal meningitis cases has climbed to 91, with seven deaths and perhaps thousands of others infected.

The Centers for Disease Control and Prevention says most of the cases are in Tennessee, where 32 people are sick and three have died.

But authorities fear that the tainted steroid given to patients for back pain may have been sent to hospitals and clinics in 23 states and injected into thousands of people. It can take up to one month for symptoms to appear.

The company that manufactured the suspect medicine, the New England Compounding Center in Massachusetts, has recalled the steroid and shut down.

Meningitis is a disease infecting membranes protecting the brain and spinal cord. There are five different types. The current outbreak is caused by a fungus, which is the rarest form of the disease. Other types are caused by bacteria, a virus or a parasite.