Officially, the CDC reported on Thursday that it has confirmed 51 cases of the polio-like syndrome in 19 states, all of them occurring since August 1. But on Wednesday evening, when the moderator of the special session asked the 250 or so child neurologists in attendance how many had seen a recent case, about one-third raised their hands. Dozens kept their hands up when asked if they had seen two, three, five or more.

“That’s pretty remarkable,” said James J. Sejvar, the neuroepidemiologist at the CDC who is tracking the outbreak, in a telephone interview from Atlanta. “I would concur with the folks in attendance that the true number of cases is larger than the 51 we have identified so far. There are probably in reality over a hundred cases nationwide. How much more is difficult to say.”

Some of the children have had mild to moderate recovery of strength, doctors at the meeting said. But asked whether they had seen a complete recovery in any of their patients, only two of the doctors at the meeting raised their hands.

The moderator, Max Wiznitzer, a child neurologist at Case Western Reserve University School of Medicine in Cleveland, said that he and other neurologists are working closely with the CDC to put together treatment guidelines.

But, he said, “The bottom line is that right now we don’t have an effective treatment.”

Some doctors at the meeting said they fear the number of cases could be much higher than 100.

“I was on a conference call a few weeks ago with about 50 doctors from medical centers across North America,” Van Haren said. “Every center had seen cases. That puts the numbers real high, real fast.”

Neurologists suspect the current outbreak to be a rare but grim effect of the far larger epidemic of enterovirus 68 infections that occurred across North America this summer. That link, however, has yet to be proved. Even so, as cases of severe respiratory illnesses associated with the virus have waned with the advent of colder weather, so too have the cases of acute flaccid myelitis.

Since August, 13 cases have been seen in Colorado, according to Teri L. Schreiner, a pediatric neurologist at Children’s Hospital in Denver. Clusters of cases have also been reported by neurologists in Missouri, Alabama, New York, Michigan, and Massachusetts.

When asked by Wiznitzer how many doctors had seen as many as 10 cases in recent months, Brenda Banwell, chief of neurology at Children’s Hospital of Philadelphia (CHOP), raised her hand. At the CDC, Sejvar said, “It definitely appears that CHOP is seeing a large number of children with this presentation.”

Mark Gorman, a child neurologist at Boston Children’s Hospital, said he has seen six cases there since August 1.

“I’ve heard from colleagues in the region who have seen other patients,” he said by telephone.

While most of the doctors attending the conference said they had rarely, if ever, seen anything like the recent cases of paralysis, Gorman said he had seen a similar condition affect five children, back in 2008.