The Washington Department of Health announced Thursday they are investigating a possible sixth case of a rare condition that can cause a “sudden onset of paralysis of one or more limbs.”

The children, who are all under the age of 6, are being evaluated for acute flaccid myelitis (AFM), a condition that affects a person’s nervous system and can cause paralysis.

Two cases were reported in King County. Three other cases were reported in Pierce, Lewis, and Snohomish counties. The latest patient is from Skagit County.

At least five of the children showed systems of a respiratory illness the week before developing symptoms of AFM. Four of the children had a fever of 100.4 or higher, the Department of Health said Wednesday.

Dr. Elizabeth Meade, chief of pediatrics at Swedish Pediatrics, says AFM is more common in kids and is sometimes associated with viruses.

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The Washington Department of Health is working with the Centers for Disease Control and Prevention to confirm if the children have AFM.

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

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Editor’s Note: The video above was originally published in 2016.

Doctors currently don’t know a lot about how AFM spreads.

“What we do know is that AFM can be caused by lots of different things, and one of those things is a viral infection,” Dr. Meade said. “So, we’ve seen that there’s an association between viruses, specifically enterovirus, in the past. That enterovirus is transmittable from person to person, but you can’t actually catch AFM from somebody else.”

However, a person can catch a virus from someone that leads to AFM.

“But just because you catch the virus from somebody that developed AFM, doesn’t mean that you will also develop AFM,” Dr. Meade explained.

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Doctors call severe cases of AFM a polio-like illness where people will have paralyzed limbs. Dr. Meade said sometimes people recover from the paralysis, but others don’t recover even after several years.

There is no vaccine for AFM or a vaccine for enterovirus.

The CDC estimates that less than one in a million people will get AFM every year in the United States. Between January 1 to September 30, 2018, 38 people in 16 states have been confirmed to have AFM.

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Nine cases of AFM were reported in Washington state in 2016. Three cases were reported in 2017, and one other case was reported in Washington since the beginning of 2018. The five cases under investigation have not been confirmed.

The health department says there are no specific recommendations for avoiding AFM, but washing your hands, avoiding close contact with sick people, cleaning surfaces with disinfectants, and staying up-to-date on immunizations is recommended.