CDC Investigates Cases Of Neurological Illness Causing Weakness, Paralysis - Cause Unclear

Acute Flaccid Myelitis Cases Rise: CDC Investigates Cases Of Rare Neurological Illness - Cause Unclear

A rare condition causing weakness in the arms or legs — and sometimes paralysis — has been confirmed in 62 children so far this year, the Centers for Disease Control and Prevention said Tuesday.

One child has died of the condition, called acute flaccid myelitis, or AFM.

At least 65 more cases are under investigation, said Dr. Nancy Messonnier, director of the CDC's National Center for Immunization and Respiratory Diseases. So far, a common cause linking these illnesses has not been found.

"There is a lot we don't know about AFM," Messonnier said during a teleconference for reporters. "I am frustrated that despite all of our efforts, we haven't been able to identify the cause of this mystery illness."

The average age of the children is about 4, she said, and 90 percent of cases the CDC has been studying since 2014 have involved patients 18 or younger.

Messonnier said scientists don't fully understand the long-term consequences of the illness: "We know that some patients diagnosed with AFM have recovered quickly and some continue to have paralysis and require ongoing care."

Since the condition was first recognized by CDC in 2014, the agency has confirmed 386 cases through Oct. 16, mostly in children. AFM appears to be seasonal, occurring mostly in the late summer and fall, but appears in greater numbers every other year. 

The number of cases in 2018 is on track to match a similar number of cases in 2014 and 2016. But Messonnier cautioned that it would be "premature" to be confident that this year will be the same as the earlier years.

It's possible that some milder cases haven't been reported by doctors to their state health department or the CDC, but Messonnier believes that number would be small. 

"This is actually a pretty dramatic disease," she said. "These kids have a sudden onset of weakness and they are generally seeking medical care and being evaluated by neurologists, infectious disease doctors and their pediatricians and coming to public health awareness."

Possible causes being considered include viruses that affect the digestive system called enteroviruses, and possibly strains of rhinoviruses, which cause the common cold, she said. The CDC is also considering the possibility that environmental toxins could be triggering the sudden muscle weakness. And it is not ruling out possible genetic disorders.

Media reports in recent weeks have suggested that a "polio-like virus" might be triggering the condition, elevating fears that it might be polio itself.

"Right now, we know that poliovirus is not the cause of these AFM cases," Messonnier said.

She said that CDC has tested every stool specimen from AFM patients. None have tested positive for poliovirus. She also said West Nile virus hasn't been linked to any of these cases, either.

Most states facing confirmed or possible cases of polio-like illness

This year, more than half of all US states have had confirmed or possible cases of acute flaccid myelitis, the polio-like illness that can cause paralysis and mostly affects children, according to an exclusive CNN analysis.

CNN reached out to health departments in every state; 48 states responded, plus the District of Columbia. Of those, 30 states said they had cases that were confirmed, suspected or being investigated -- including 15 states that said they had confirmed cases in 2018.

In total, CNN found 47 confirmed cases and 49 more that were suspected or being investigated, for a total of 96.

The US Centers for Disease Control and Prevention, which releases only confirmed numbers, says 16 states had 38 cases as of September 30. It does not identify the states.

CNN found that Colorado had 14 confirmed cases, more than any other state, followed by Texas with eight and Minnesota with six.

Acute flaccid myelitis, also called AFM, is a rare but serious condition that affects the nervous system, with a particular focus on the gray matter of the spinal cord. It affects fewer than one in a million people each year across the country, the CDC estimates.

The agency has seen an increase in cases since August 2014. Although the cause remains a mystery in the majority of cases, the 2014 jump coincided with "a national outbreak of severe respiratory illness among people caused by enterovirus D68," though it wasn't found in all patients, according to the CDC.

Other enteroviruses have also been found in patients with AFM. For example, 11 of the Colorado cases of AFM this year have tested positive for EV A71, a rare type of enterovirus not usually seen in the US, rather in Asia and other parts of the world, according to state epidemiologist Dr. Rachel Herlihy. 

"The most common etiology is probably a viral infection that starts off the process, and there's probably several different viruses that can cause acute flaccid myelitis," said Dr. Samuel Dominguez, medical director of the clinical microbiology laboratory at Children's Hospital Colorado.

In addition to viruses, potential causes may include environmental toxins and genetic disorders, according to the CDC, and it "can be difficult to diagnose because it shares many of the same symptoms as other neurologic diseases." It is not a reportable disease in all states.

Symptoms can include sudden limb weakness, loss of muscle tone and reflexes, facial and eyelid drooping, difficulty moving the eyes, difficulty swallowing, slurred speech and, in the most severe cases, difficulty breathing, according to the CDC. What happens to patients down the line is unclear; some recover quickly, while others may need long-term care.