Rare Neurological Disease Investigated in Mysterious Washington State Illness Cluster

— -- A cluster of children who developed neurological symptoms in Washington state has put the spotlight on a rare and frightening syndrome called acute flaccid myelitis (AFM.) The syndrome affects the nervous system, especially the spine, and can lead to temporary or permanent paralysis of the limbs.

Two of the hospitalized children were confirmed to have AFM and seven other cases are under investigation. One child who died, though the cause of death has not yet been confirmed, experienced the same severe neurological symptoms.

Yesterday, the Centers for Disease Control and Prevention (CDC) released new numbers about the disease, which show an uptick in cases this year. At least 89 people have been diagnosed with AFM in the U.S. as of September. In 2015, there were a total of 50 cases.

"CDC is concerned about AFM, a serious illness that we do not know the cause of or how to prevent," the agency wrote on its website.

The frightening syndrome also made headlines in 2014 when 120 cases were reported, most of them in children. While experts from the CDC investigated the outbreak to look for a cause, they have yet to identify a single pathogen that led to the outbreak.

What is acute flaccid myelitis?

AFM is a condition that affects the nervous system, specifically the spinal cord, and can cause temporary or permanent paralysis in one or more limbs.

The word myelitis refers to an inflammation in the spinal cord.

Symptoms of AFM include weakness or paralysis of the limbs, facial droop, difficulty breathing and drooping eyelids, according to the CDC. If the muscles involved in breathing become too weak to function, the syndrome can turn deadly and a patient may need to be put on a ventilator to survive.

What causes the syndrome?

AFM can be caused by a variety of infections, including viral illness such as enteroviruses, which includes the polio virus, West Nile virus and adenoviruses. However, identifying a cause for a cluster of cases can be difficult. In 2014, CDC officials looked for signs that an outbreak of enterovirus D68 had caused the subsequent AFM outbreak, but they never found a clear link between that specific viral infection and the syndrome.

"To date, we have not consistently detected a pathogen (germ) in the patients' spinal fluid; a pathogen detected in the spinal fluid would be good evidence to indicate the cause of AFM since this illness affects the spinal cord," the CDC said on their website.

State health officials investigating the Washington state cluster of cases said no link between them has been identified. The nine children hospitalized lived in four different counties.

"We’re looking at all possible causes of the AFM cases in 2016," a CDC spokesman told ABC News today. "We know that certain viruses can cause AFM, such as enteroviruses, adenoviruses, and West Nile virus, but we don’t know what’s causing these cases of AFM in 2016 specifically."

How is it treated?

No specific treatment has been proven to stop AFM, but doctors can take steps to diminish dangerous inflammation in the nervous system.

How often does AFM appear in the U.S.?

Tracking the number of AFM cases in the U.S. has not been consistent. The outbreak in 2014 led the CDC to ask doctors to look for and report the disease. From August to December 2014 the agency received at least 120 reports of AFM cases, in 2015 50 cases were reported and, as of September this year, 89 cases have been reported.

AFM is one type of the condition called transverse myelitis. In the neurological disorder, inflammation occurs on both sides of one segment of the spinal cord, according to the National Institutes of Health (NIH).

The NIH states, "1,400 new cases of transverse myelitis are diagnosed each year in the United States, and approximately 33,000 Americans have some type of disability resulting from the disorder."