A deadly outbreak of infections linked to tainted steroid injections is approaching 500 cases nearly two months after it began, and health experts said on Wednesday it was unclear whether the epidemic had peaked amid new risks facing patients.

Many patients initially stricken with fungal meningitis are developing secondary infections, prompting a renewed effort to contact people who received the injections, said health officials in Tennessee and Michigan, the two hardest-hit states.

The outbreak, first detected in Nashville, Tennessee, in September, has stricken at least 490 people in 19 states, with 34 deaths, according to the U.S. Centers for Disease Control and Prevention in Atlanta.

“I wouldn’t want to characterize the epidemic as having reached a peak or (say) that we are over the worst part,” Dr. J. Todd Weber, the CDC’s incident manager, said on Tuesday.

Weber said many patients face weeks to months of additional treatment, more people may get sick, and there is more to learn about the infections to ensure the best care for those stricken.

The CDC has estimated that 14,000 patients received potentially tainted steroids believed to have been prepared in unsanitary conditions by a Massachusetts-based compounding pharmacy and shipped to customers in 23 states from May to September.

The rate of infection, based on 500 cases out of 14,000 people exposed mainly through injections to relieve back and joint pain, has been about 3.5 percent so far, somewhat lower than the 5 percent rate Tennessee first forecast, Weber said.

Tennessee was the epicenter of the outbreak early on and through Wednesday had reported 84 infections, including 13 deaths. Michigan through Wednesday had reported 64 meningitis cases and 91 incidences of epidural abscesses among a total of 164 patients, a number of whom had both.

Most of the early cases were of meningitis, but reports more recently have been of abscesses at the injection sites, many times in patients already being treated for meningitis, officials in Michigan and Tennessee said on Wednesday.

INCUBATION TIME UNCERTAIN

That makes it hard to determine how long the outbreak of steroid-related infections might yet last, officials said.

“These are presenting well into the course and I don’t think with the epidural abscess that we’ve been able to establish a real concrete incubation time,” said Jim Collins, director of the Michigan health department’s communicable disease division.