The federal Centers for Disease Control and Prevention has now said it has received reports of 127 suspected cases of acute flaccid myelitis or AFM, a polio-like condition that affects the central nervous system. So far, 62 cases of the illness have been confirmed in 22 states. In Michigan, health officials are investigating at least one suspected case.

AFM mimics cold or flu symptoms at first, but a sudden onset of limb weakness and loss of muscle tone and reflex is a signal that a child’s ailment may be far from ordinary. Some with the illness may notice facial droop or weakness, difficulty moving eyes, drooping eyelids, or difficulty swallowing or slurred speech, according to the CDC.

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In some rare cases, AFM may cause numbness or tingling in the limbs, the inability to pass urine and breathing difficulties due to muscle weakness that require urgent ventilator support, the CDC said.

The CDC doesn’t list the states where AFM has been confirmed, but CNN said its survey of state health departments revealed it has been confirmed in Arizona, Colorado, Georgia, Indiana, Iowa, Massachusetts, Minnesota, New Jersey, North Carolina, Ohio, Pennsylvania, Rhode Island, South Carolina, Texas and Wisconsin.

Health officials in Alabama, Arkansas, California, Florida, Illinois, Kentucky, Louisiana, Maryland, Massachusetts, Michigan, Montana, Nebraska, Nevada, New York, North Carolina, Oklahoma and Washington are reviewing suspected cases of the illness.

It’s unclear what is causing what could be a spike in AFM, first recognized by the CDC in 2014. Since then, the CDC has confirmed 362 cases, and the number of cases is growing every year, the CDC’s Dr. Nancy Messonnier told reporters in a conference call Tuesday.

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So far, she said, officials haven’t found a common link among the reported illnesses, which can develop after a viral infection.

“There is a lot we don’t know about AFM,” Messonnier said. “I am frustrated that despite all of our efforts, we haven’t been able to identify the cause of this mystery illness.”

Acute flaccid myelitis can be caused by a variety of germs, including several viruses, according to the CDC, including both polio and non-polio enteroviruses, West Nile virus and viruses in the same family, and adenoviruses. Environmental toxins and genetic disorders may also cause AFM, according to the CDC, which said AFM is only one of a number of conditions that can result in neurologic illness with limb weakness.

Oftentimes, however, a cause for AFM cannot be identified.

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