By Susan Levine
The nation’s disease detectives are on the lookout for the return of a frightening illness that paralyzed 115 children in 34 states last fall and early winter.
They don’t have much to go on. 
The United States has built up its public health response and surveillance since the 2001 terrorist attacks and lethal anthrax letters. But even with the tools now available, neither the Centers for Disease Control and Prevention nor state health officials have established what caused that polio-like syndrome or whether it was related to the powerful respiratory virus that sickened more than 1,100 people across the country.
And they don’t know if another outbreak is likely to occur later this year.
They readily acknowledge the challenge. “It’s a fantastic medical mystery,” said James Sejvar, a CDC neuroepidemiologist. “But clinically, it’s quite frustrating.”
The first cases of paralysis started surfacing in September. From California to Massachusetts, children on the back end of a bad respiratory infection suddenly couldn’t raise arms, move legs or, in some instances, breathe without assistance.
When it finally waned several months ago, almost as abruptly as it had begun, the outbreak left distressingly few clues about its cause. For many of the families affected, the aftermath has been devastating. Most children have not fully recovered, and a third haven’t improved at all.