Mysterious ‘polio-like’ illness AFM is likely more widespread than reported, experts say
A “polio-like” condition that has left children in 22 states paralyzed may be more widespread than previously announced due to inadequate testing protocols and voluntary reporting requirements, experts say.
The Centers for Disease Control and Prevention reported that there have been 62 confirmed cases of Acute Flaccid Myelitis so far this year.
Since the first known outbreak of AFM in 2014, the devastating illness has reemerged with at least 50 confirmed cases between August and October in even-numbered years.
AFM often begins with signs of a respiratory infection but quickly progresses. Within a few hours, patients may have difficulty breathing and develop “flaccid weakness,” and one or more limbs may become paralyzed.
The emergence of AFM — also known as Acute Flaccid Paralysis, or AFP — coincided with a 2014 outbreak of EV-D68, an enterovirus associated with respiratory illness.
While a number of factors can cause AFM, including viruses, environmental toxins and genetic disorders, the exact cause of most cases isn’t known.
“I think the challenge is that we haven’t found one specific virus that is causing these complications,” said Dr. Devorah Segal, a pediatric neurology expert at Weill Cornell Medical College and NewYork-Presbyterian Hospital.
“I don’t think we really understand why there have been peaks at these two-year intervals.”
AFM and polio, which has been eradicated in most areas of the world, share some similarities and some differences.
Polio inhabits the gastrointestinal tract and replicates in the stomach and intestines. Common symptoms include stomach pain and nausea.
Enteroviruses like EV-D68, meanwhile, show signs of respiratory infections and can spread through airborne contact. They replicate in the back of the throat and can be detected through a swab taken through the nose to the back of the throat.
This means the kinds of tests that are used to detect polio — such as stool samples — may not be effective in detecting an enterovirus, potentially causing the outbreak. Tests of spinal fluid have also been used to try to detect the presence of a virus, but like polio, enteroviruses are often not detectable in spinal fluid although a patient may be infected.
“To date, no pathogen (germ) has been consistently detected in the patients’ spinal fluid; a pathogen detected in the spinal fluid would be good evidence to indicate the cause of AFM since this condition affects the spinal cord,” the CDC wrote.
Completing a nasal swab test where enteroviruses thrive can help pinpoint the presence of a specific virus or viruses present for people suffering from AFM, said Dr. Benjamin Greenberg, a neurologist at UT Southwestern and Children’s Health in Dallas.
“If you do that test correctly and within a few days when someone shows up with paralysis, [I think we would see that] overwhelming case of kids tested appropriately and correctly would show up with the D68 virus,” Greenberg said.
Greenberg, one of the nation’s foremost AFM researchers, has treated children with AFM when the disease spiked in previous years.
While the CDC reports the first cases of AFM connected to EV-D68 in 2014, Greenberg said there were cases that may have been linked as early as 2012 in California.
Because not all the same tests are done all the time — some hospitals and doctor’s offices don’t have the capabilities to test for specific types of enteroviruses — in addition to the lack of mandatory reporting, it is difficult to determine if other viruses besides EV-D68 are causing the AFM outbreaks.
“I still think EV-D68 may be driving a lot of this,” Greenberg said. “I can’t prove this, but there is a lot of circumstantial evidence to suggest this.
“A group in Colorado showed circulating EV-D68 would paralyze a mouse, but EV-D68 in a freezer from the ’60s did not… the virus changed, and the virus as of 2014 or 2010 was capable of causing paralysis.”
Enteroviruses rarely lead to paralysis. People who contract a virus often only have symptoms of a common cold or respiratory infection.
A number of factors could contribute to the recurring timing of the AFM outbreaks. The environment and characteristics that allow a virus to thrive — such as temperature, humidity levels or dew point — could be key in determining why the outbreaks have occurred on an every-other-year basis with most cases appearing from August to October since 2014.
While AFM remains rare, Greenberg fears that AFM could pose a more widespread threat if EV-D68 continues to mutate, and he believes the skip-year AFM trends since 2014 will continue in the future.
“If the pattern keeps up… in 2019 we will see significantly less cases,” he said. “It won’t be zero, but it will be significantly less. And I have no reason to suspect that in 2020 we won’t see an increase again.”