Six children are hospitalized in Washington with symptoms that match a rare polio-like disease that has seen a spike this year.

The children, all younger than 6, had respiratory illnesses the week before they developed symptoms of acute flaccid myelitis, according to the Washington State Department of Health. While few people die from acute flaccid myelitis, problems breathing can require ventilator machines or the condition can trigger other neurological problems.

As of the end of September, federal authorities had confirmed 38 cases of acute flaccid myelitis across 16 states in the U.S. Washington health authorities said they are waiting for confirmation from the U.S. Centers for Disease Control about the children currently hospitalized.

One child in Washington was confirmed earlier this year to have acute flaccid myelitis. Last year, three children in Washington had the disease, and nine did in 2016 during a national peak in the disease.

That year, Oregon had at least three cases and three in 2014. The Oregon Health Authority has not reported any cases so far this year.

The disease affects fewer than 1 in 1 million people in the U.S., according to the federal agency. However, its scientists have paid more attention to it since 2014 when the rates of the disease started to grow.

In 2014 and 2016, especially, the number of people with acute flaccid myelitis jumped from August to October.

Doctors have been unable to pinpoint a common cause for acute flaccid myelitis. In many cases, no one is able to name a cause, according to the Centers for Disease Control.

"At this point there isn't evidence that would point to a single source of illness among these cases," said Dr. Scott Lindquist, state infectious disease epidemiologist at the Washington State Department of Health. "We're working closely with medical providers and public health agencies. We'll continue to investigate and share information when we have it."

The disease is similar to polio and West Nile Virus, and the Centers of Disease Control said that those two viruses, as well as non-polio enteroviruses and mosquito-born illnesses like Zika, could also cause acute flaccid myelitis.

Acute flaccid myelitis causes a sudden weakness in one or both arms or legs. People with the condition also lose muscle tone and reflexes, experience facial and eyelid drooping, difficulty moving their eyes, difficulty swallowing or speaking.

Health authorities say they don't know what the long-term consequences of acute flaccid myelitis are or who is most at risk of contracting it.

Since there is no determined cause, there is no sure-fire treatment or prevention. The federal government recommends people wash their hands with soap and water, disinfect surfaces and avoid contact with sick people.

Health authorities also recommend staying up to date on vaccines, especially for polio, and avoiding mosquito bites whenever possible.

-- Molly Harbarger

mharbarger@oregonian.com

503-294-5923

@MollyHarbarger