CDC: Meningitis Mold In Tainted Drug Can Incubate For Months

by Richard Knox

October 20, 2012 7:00 AM

As the caseload of fungal meningitis linked to a tainted steroid drug climbs, experts are learning more about this human-made epidemic. The signs indicate that cases could still be emerging until Thanksgiving or beyond.

The latest count is 268 cases of meningitis and three patients with fungal joint infections, spread across 16 states from New Hampshire to Texas and Idaho to Florida. Twenty-one people have died.

The illness is caused by a fungus called Exserohilum rostratum, a black mold that usually attacks plants. It's so rare as a cause of human illness that nobody knows its incubation period.

So it's hard to predict when the outbreak will be over, even though presumably no patients received the contaminated steroid since the Massachusetts pharmacy that made it recalled three lots on Sept. 21.

"The incubation period is something that's been a big question," Dr. Tom Chiller of the Centers for Disease Control and Prevention told a Thursday evening session of the IDWeek meeting in San Diego.

"The majority [of cases] have incubation periods around one to four weeks, but we've clearly seen documented periods beyond that," he said.

Chiller told Shots that none has been beyond two months so far. That's based on 155 cases for which the CDC has firm dates for steroid injection and symptom onset. The incubation period is hard to calculate, though, because many patients had multiple injections of potentially contaminated methylpredisolone made by the New England Compounding Center.

The CDC says infections following steroid injections into ankles, knees, hips, shoulders or elbows "may take longer to develop than fungal meningitis."

Even more sobering, the meningitis incubation period was as long as five months in an eerily similar outbreak of mold-contaminated methylprednisolone in North Carolina back in 2002.

Dr. John Perfect of Duke University recalls that outbreak in an article published online by the Annals of Internal Medicine on Thursday.

"We learned, or thought we learned, several important lessons from the outbreak," Perfect writes.
One of them is that mixing preservative-free steroid drugs such as the one involved in both outbreaks "requires meticulous sterility to ensure lack of fungal contamination," he says. Anything less and fungi "grow aggressively" in a highly concentrated steroid solution.
But there are encouraging signs. For both the 2002 episode and the current one so far, the "attack rate" is apparently low. That is, few of those injected with the contaminated steroid get sick — for unknown reasons.
That's an inference from the fact that public health authorities estimate 14,000 people got the tainted injections since May 21. While no one can say how many people ultimately will get sick, at least it's not in the thousands so far.
Second, the CDC's Chiller says more recent cases are less sick.
"Early in the outbreak, we saw more advanced disease," he says. "Now, as we've reached out to all these patients, we're identifying people early and symptoms are very mild."
CDC officials say that 97 percent of the 14,000 people thought to have received the contaminated steroid have been reached and advised to watch for signs of infection.
Continue reading the full NPR story here