Michigan health officials have confirmed the first local case of a polio-like illness that has sickened 134 people — mostly children — nationwide in 2018.

Acute flaccid myelitis affects the nervous system, causing muscles and reflexes to become weak.

The sick child is from Wayne County, according to the Michigan Department of Health and Human Services. Additionally, seven suspect cases of AFM in the state are under investigation.

The disease is not new, but there has been an increase in cases since 2014, according to the Centers for Disease Control and Prevention. The agency announced in November that it was setting up a task force to investigate what causes AFM and find better treatments for patients.

More than 90% of people who get the disease are children.

More:What to know about polio-like illness in Michigan: CDC tracking 4 cases

Patients often experience the sudden onset of arm or leg weakness and the loss of muscle tone and reflexes. Other symptoms can include facial droopiness or weakness, difficulty moving the eyes, drooping eyelids, difficulty with swallowing or slurred speech.

Most people had a respiratory illness or fever consistent with a viral infection before developing AFM, according to the CDC.

The agency said the risk of getting the rare disease varies by age and year. It has been reported in 33 states so far in 2018.

"We have seen increases in AFM cases every two years since 2014 and mostly in young children," the CDC said on its website. "Still, CDC estimates that less than one to two in a million children in the United States will get AFM every year."

There is no specific treatment, the CDC said, though specialists may recommend certain interventions on a case-by-case basis.

For more information, visit the Michigan Department of Health and Human Services' Communicable Disease Information and Resources website or the Centers for Disease Control at CDC.gov/AFM.

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USA Today contributed to this report. Contact staff writer Ann Zaniewski at 313-222-6594 or azaniewski@freepress.com. Follow her on Twitter: @AnnZaniewski.