The Centers for Disease Control and Prevention (CDC) is looking into an extremely rare condition that is being described as a polio-like illness for its ability to cause weakness and paralysis in children.
"CDC continues to receive information about cases of acute flaccid myelitis (AFM), a serious condition that causes weakness in the arms or legs," CDC spokesperson Kate Fowlie told SELF in a statement. "So far in 2018, CDC has confirmed 62 cases of sudden onset AFM in 22 states. Of those, 90 percent are in kids 18 and younger and the average age is 4."
AFM affects the nervous system, causing sudden weakness in the arms and legs.
"It specifically affects the area of the spinal cord called gray matter and causes muscles and reflexes to become weak," Nancy Messonnier, M.D., director of the CDC’s National Center for Immunization and Respiratory Diseases, said in a press conference on Tuesday.
In addition to a loss of muscle tone and reflexes in the limbs, some people may also have facial drooping or weakness, drooping eyelids, difficulty moving the eyes, difficulty swallowing, slurred speech, an inability to pass urine, pain in the arm and legs, and (less commonly) numbness or tingling, according to the CDC. The most severe cases of AFM can lead to respiratory failure (due to a weakening of the muscles that help you breathe) or the development of potentially fatal neurological complications.
Diagnosing AFM involves a physical exam to assess how well the patient's nervous system is functioning, as well as tests including an MRI of the patient's brain and spinal cord and lab tests of their cerebrospinal fluid. Unfortunately, the current treatment options for AFM are extremely limited—and there is actually not any specific treatment, according to the CDC. But neurologists can make recommendations—like physical therapy to manage muscle weakness—on a case-by-case basis.
Recovery varies from person to person. Some patients are able to recover relatively quickly, while others continue to have paralysis, but experts don't know why that is, Dr. Messonnier said.
The illness isn't new—the CDC and epidemiologists have had it on their radar for years.
The first increase in the reported number of cases was in 2014, according to the CDC. Between August 2014 and September 2018, the agency has been alerted to 386 confirmed cases in the U.S., and there has been one confirmed death related to AFM (in 2017).
- In 2014, there were 120 cases in 34 states.
- In 2015, there were 22 cases in 17 states.
- In 2016, there were 149 cases in 39 states.
- In 2017, there were 36 cases in 16 states.
As you can tell from those numbers, "AFM has been occurring in waves about every two years," infectious disease expert Amesh A. Adalja, M.D., senior scholar at the Johns Hopkins Center for Health Security, tells SELF. "Every time, it always ends up being a new news story. But this isn’t something people have been ignoring. It’s something they've been actively investigating since 2014."
During the press conference, Dr. Messonnier said that the numbers so far indicate that we are on track to see a similar number of cases as we saw in 2014 (120) and 2016 (149). "But it would be premature to say that we’re confident that we know what is going to happen since it really is early in this." And given that we only have four years of data and fewer than 400 cases to go on, it's hard to say for sure. But rest assured, the CDC is closely tracking the situation.
Although the CDC has been able to find the apparent trigger in some cases—including enterovirus, West Nile virus, environmental toxins, and an autoimmune condition—they haven't figured out a singular cause.
"For individual cases we are finding agents, but nothing that provides the unifying diagnosis that we expect to explain this disease," Dr. Messonnier explained. "Despite extensive laboratory testing, we have not determined what pathogen or immune response caused the arm or leg weakness and paralysis in most patients," she said. "I am frustrated that despite all of our efforts we haven’t been able to identify the cause of this mystery illness."
But we may not find a unifying diagnosis for AFM, Dr. Adalja says. "It’s unlikely we’re going to find a single cause because we would've gotten it by now," Dr. Adalja says. "It may not fit into a neat category."
One theory, he says, is that common cold-like viruses may in rare circumstances cause AFM symptoms. "It may be an overlapping syndrome that certain viruses have the capacity to cause in certain individuals—an interaction between the infection agent and the immune system of the person," he explains. "It’s important that we start to unravel the mysteries of AFM and determine which viruses are responsible for causing it." (One thing we do know: It's not polio. The CDC has tested stool samples of patients for the polio virus, Dr. Messonnier said.)
The CDC is also working to gather more information on other poorly understood aspects of the illness, like risk factors, the trajectory of the illness, and prognosis. "We don’t know who may be at higher risk for developing AFM or the reasons why they may be at higher risk. We don’t fully understand the long-term consequences of AFM," Dr. Messonnier said.
Despite all of the unanswered questions, it's important to keep in mind how uncommon this condition still is.
"With the unpredictability and the mystery around who gets AFM and who doesn't, it's understandable that people get alarmed by it," Dr. Adalja says. "But it's important to understand that it's very, very, very rare. You should not expect every cold your child gets to cause this." In fact, fewer than one in a million Americans will contract AFM every year, the CDC estimates.
Of course, if you notice any of these symptoms in yourself or your child, seek medical care immediately. But "it isn't something that should occupy the minds of every American," as Dr. Adalja puts it. As he points out, it's more important to prepare for the upcoming flu season, given how much more likely people are to develop a severe case of the flu—even if AFM dominates the headlines.