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The number of new cases of the polio-like paralyzing condition called acute flaccid myelitis appears to be peaking, federal health officials said Monday.

The Centers for Disease Control and Prevention said it has confirmed 134 cases of AFM, out of 299 suspected cases in 33 states.

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“It appears that the number of persons under investigation for AFM has peaked and will continue to decline for the remainder of 2018,” the CDC said in a statement.

Most of the newly reported cases appear to have occurred in September and October, the CDC said. There can be a lag of several weeks in reporting cases of disease.

Outbreaks of the condition, which causes muscle weakness and paralysis, have followed an every-other-year pattern and this fits in with patterns of viral diseases, doctors studying AFM say. The CDC and most experts believe a virus or viruses are causing the condition, which resembles polio.

The CDC stresses that the affected patients, most of them children, do not have polio. The polio virus was eliminated from most of the world by vaccination and is very rare now. Vaccines are also not associated with the condition.

But viruses can attack the nerves directly as polio virus does. Or they can set off an auto-immune reaction that damage nerves, as Guillain-Barre syndrome does. Most experts believe viruses are causing the very rare condition, although no one can say if any single virus is the cause, or if several different viruses are to blame.

“CDC expects states to continue reporting likely AFM cases, and medical experts will continue to review them and determine if they are confirmed. CDC will continue to provide updates on the number of confirmed cases of AFM,” the agency said.

The decline in cases is expected to continue. “Although fewer cases are expected in coming months, CDC and partners continue to carefully study AFM to gain new understanding of the condition so that we can better diagnose, treat, and prevent it in the future,” the agency said.