A ninth child in Washington has been diagnosed with a rare, polio-like disease.

Share story

A ninth child in Washington has been diagnosed with a rare, polio-like disease.

Health officials confirmed Tuesday that a Spokane County boy under age 10 is suffering from acute flaccid myelitis, or AFM.

AFM is characterized by inflammation of the spinal cord, which results in limb weakness or paralysis. But the cause of the inflammation remains a mystery.

The U.S. Centers for Disease Control and Prevention (CDC) is working with local health officials to investigate the unusual cluster of cases in Washington this fall.

The condition also appears to be on the upswing nationwide, with 89 cases reported from 33 states so far this year, up from 21 cases in 2015.

AFM can be triggered by certain types of viruses that normally infect the respiratory tract. It has also been associated with West Nile virus, autoimmune diseases and environmental toxins. But for most cases in the U.S., a definitive cause has never been pinned down.

So far, no common factors have been identified among the affected children in Washington, said Dr. Scott Lindquist, Washington’s state epidemiologist for communicable diseases.

“There’s been no clear underlying cause of it, which has been the frustrating part,” he said.

Officials are interviewing all the families, using an extensive questionnaire. They have also analyzed blood, sputum and stool samples, which are then sent to the CDC for more extensive testing.

All the testing is not complete, but there is no preliminary evidence to implicate any particular virus or chemical exposure, Lindquist said. Nor is there any indication that any of the children was vaccinated or received other injections shortly before falling ill, he said.

The affected children in Washington come from six different counties: King, Pierce, Snohomish, Whatcom, Franklin and Spokane.

AFM was ruled out as the cause of paralysis in a 6-year-old Bellingham boy who fell ill earlier this fall and died Oct. 31.

One possible case in King County is still being investigated.

With no known cause, officials can only advise generic precautions against infection, such as washing hands and avoiding sick people.