(Undated) — Researchers and health officials are seeing a rise in a virus that causes paralysis in children. Enterovirus D68 is a respiratory illness that, in rare cases, can cause paralysis that doctors compare to polio.

An analysis of 17 wastewater sites in Sacramento, San Francisco, Los Angeles, San Diego, and San Jose resulted in detection in about half of the samples. A nationwide study detected the virus in 207 of 268 samples.

Nine out of ten infections are in children, with asthma sufferers more susceptible to it. There is no known cure.