They're linked to medication made by the New England Compounding Center. Massachusetts Governor Deval Patrick says the company may not have had the proper licensing to make large amounts of the drug and sell them outside the state.
The incubation period for fungal meningitis is one to four weeks, but health experts say it may take much longer for symptoms to appear.
Health officials say only between one and five percent of those who are exposed get sick.
The New England Compounding Center settled a lawsuit several years ago with a woman who claimed her husband died of bacterial meningitis after receiving a shot made by the company.
Two clinics in Pennsylvania including one in Altoona received the recalled medicine, but local doctors say it was returned unused. There are no cases of fungal meningitis in Pennsylvania related to the outbreak.