You’ve probably heard about hundreds of people who developed meningitis after receiving steroid shots from a tainted production match. As the Associated Press reports, what’s complicated diagnosis and treatment is that the resulting infection is something completely new:

Most of the positively identified cases are caused by Exserohilum rostratum (ex-sir-oh-HY-lum ross-TRAH-tum). The fungus is commonly found in the environment, but it has never before been observed as a cause of meningitis.

Because of that, [Dr. David Reagan, medical officer for Tennessee] said, officials have been unable to firmly establish the incubation period and give those who received the tainted injections a date for when they will no longer need to worry about developing meningitis.

“We’re saying at least six weeks, or 42 days, but we probably will extend that,” he said. “This is new territory. There’s no literature to tell us how long.”

Reagan notes that treatment is very effective if given early, but not that effective if given later.

Update: Another AP story here.

The main culprit in this outbreak is a black mold called Exserohilum rostratum , common in dirt and grasses. Only 33 human infections previously had been reported, mostly eye or skin infections in people with weak immune systems.