There are now 286 cases of possible and confirmed acute flaccid myelitis in the United States this year, according to the US Centers for Disease Control and Prevention.
That includes 116 confirmed cases of the rare polio-like illness, also known as AFM, that leads to sudden onset of paralysis. That’s 10 more confirmed cases than the agency reported a week ago. Six of those cases are in New Jersey.
An additional 170 possible cases of AFM are under investigation.
More than 90 percent of the 440 patients with AFM since 2014 have been children younger than age 4. Most of the children with confirmed cases experienced a viral illness with symptoms including fever and cough about three to 10 days before the onset of paralysis, the CDC said this month.
The patients with confirmed AFM are in 31 states, which the CDC has now identified for the first time. There are 15 cases in Colorado, the state with the highest number, followed by Texas with 14 confirmed cases. Nineteen states have no confirmed cases, and 12 states are reporting only one confirmed case, according to the CDC.
It’s not clear whether there is more of a risk of AFM in states that have a higher number of cases or if those states are just better at identifying and reporting patients. Although the CDC has encouraged doctors to report cases, there is no requirement to do so.
Most AFM patients became ill between August and October, and according to the CDC, the number of illnesses has peaked every other fall since 2014.
Even with the rise in cases, according to the CDC, “less than one to two in a million children in the United States will get AFM every year.”
More children have been diagnosed with a mysterious paralyzing illness in recent weeks, and U.S. health officials said Tuesday that they still aren’t sure what’s causing it.
This year’s count could surpass the 149 cases seen in similar outbreaks in 2016 and 120 in 2014, officials said. Fortunately, the disease remains rare: This year, there have been 116 cases spread among 31 states, the Centers for Disease Control and Prevention said.
The state with the highest number of confirmed cases is Colorado, with 15, followed by Texas with 14.
It’s not clear what’s causing some children to lose the ability to move their face, neck, back, arms or legs. The symptoms tend to occur about a week after the children had a fever and respiratory illness. Most of the kids with confirmed cases experienced a viral illness about a week before the onset of paralysis.
Health officials call the condition acute flaccid myelitis. No one has died from it this year, but CDC officials say at least half the patients do not recover from the paralysis and some have serious complications.
Polio and West Nile virus have been ruled out. Doctors have suspected the cause might be some kind of enterovirus, which in most people causes cold symptoms. But CDC officials say that’s not clear.
The first mysterious wave of paralysis cases in 2014 coincided with a wider spike in illnesses connected to an enterovirus called EV-D68, CDC officials said. But there was no such spike during the waves in 2016 or this year.
There’s also a lack of clinical evidence: CDC officials have checked the spinal fluid of about three-quarters of 90 patients, and found EV-68 in only one. Another type of enterovirus called EV-A71 was found in only one other patient.
But there are questions about that, too. If a virus is the cause, it’s possible the test is not good enough, or the germ left the spinal fluid by the time the tests were taken, said the CDC’s Dr. Nancy Messonnier. It’s also possible the culprit is hiding elsewhere in the body.
Or perhaps the paralyzing illnesses are caused by some new germ for which no lab test has been developed. Or maybe there’s some predisposing factor in some patients that cause their immune systems to react so severely to a germ or other trigger that the immune response causes paralysis, CDC officials said.
Parents and even some scientists have criticized the agency for not solving the riddle.
“I understand why parents are frustrated. I’m frustrated. I want answers too,” said Messonnier, who is overseeing the agency’s outbreak investigation. CDC officials have pledged to do more to notify doctors to look for possible cases and to more thoroughly review cases from years past for further clues.
About 120 cases were confirmed in 2014, the first time such a wave occurred. Another 149 were reported in 2016. In 2015 and 2017, the counts were far lower, and it’s not clear why.
The illnesses have spiked in September each year there’s been a wave and tailed off significantly by November. But it can take weeks to determine which cases should be counted in the outbreak. More than 160 cases are still being investigated, and some of those may join the count, CDC officials said.