A sharp spike in cases of pediatric acute flaccid myelitis, or AFM, is raising red flags with health officials, who despite concerted efforts, haven't identified a cause.

Reporting for Reuters, Gavino Garay says AFM, is now affecting young children in 22 states following a recent spike in Minnesota.

Symptoms of AFM are similar to polio but, unlike polio, there is no vaccine for AFM. The disease affects the body's nervous system and can cause paralysis.

Parents have reported that the limbs of affected children appear lifeless.

Last year, one child died of the disease.

AFM appears to target children at around age 4. Cases have been on the rise since 2014.

Health officials are urging parents to seek immediate medical advice if their child experiences weakness or loss of muscle tone in the arms and legs.