A cryptic polio-like illness of unknown etiology is increasing, causing more severe symptoms in younger patients than when it first emerged in 2014, a CDC investigator reports.
After a decline in cases in 2015, there was more than a four-fold increase last year, including patients that presented with altered mental status and needed mechanical ventilation.
“Acute flaccid myelitis (AFM) is characterized by a sudden onset of a limb weakness, meaning an arm or a leg may lose strength or may be difficult to move,” says Tracy Ayers, PhD, an epidemiologist in the CDC Epidemic Intelligence Service. “Sometimes there’s facial drooping, sometimes there’s difficulty swallowing.”
The AFM syndrome emerged in 2014 in the U.S. in conjunction with an outbreak of Enterovirus D68 (EV-D68), which was initially strongly suspected as the infectious etiology. However, EV-D68 has been identified in some cases of AFM, but is not present in others with identical symptoms, says Ayers, who presented the investigation recently in Atlanta at the annual EIS Conference.
“EV-D68 specifically is one of the many enteroviruses that we tested for,” Ayers says. “A portion of the specimens do test positive for EV-D68, but we also have a portion that test positive for other enteroviruses, and a large portion that don’t testify positive for any of those. I think at this time it’s inconclusive what is the definitive cause. But we will continue to look at EV-D68, as well as many other enteroviruses. We’re thinking about things that are maybe non-infectious as well.”
The investigation has taken on a sense of urgency because more recent cases are striking younger children with more severe clinical presentation. Ayers and co-investigators examined a cluster of cases in children last year in Arizona.
“I was able to speak to some of the parents of some of the cases and interview them,” she says. “The idea was to explore with open-ended questions so we could learn as much as possible. They also recounted the onset of illness because this is such a new disease for us. So [we are] just learning how it progresses.”
‘The Bed Hurt’
One parent said her daughter felt fine during the day, gradually began feeling weak and ill, and by bedtime that evening had become hypersensitive and could not touch anything without experiencing pain, Ayers says.
“By the time it came time to go to bed, the bed hurt,” she says. “Everything hurt to touch. She couldn’t touch anything. So the mother put her in the bathtub because that felt better to have the water on her skin. At that point, she lost even more muscle tone and her head went a little floppy as well. So the mother was holding her in the bathtub, very scared, as you can imagine as a parent and not knowing what to do. That’s when she immediately took her to the emergency room. That’s often how these cases happen. They’re detected at the point of paralysis and taken to the emergency room.”
When Ayers examined the child two weeks later, she was regaining a little bit of strength in her upper arms and was engaged in physical therapy.
“Unfortunately, she was only one case out of 134 for 2016,” she says. “We’ve tested for over 250 different organisms that potentially could be the cause of this. We haven’t found a consistent organism causing this at this point. So we’ve expanded a lot of our laboratory testing now.”
Since the condition emerged, some cases have fully recovered and others remain at least partially symptomatic. No deaths have been attributed to AFM.
“We don’t know what the long-term outcomes are,” Ayers says. “There are very few cases and it’s brand new. We’re also working very closely with our state and public health partners because what we really want to do is make sure we [raise] awareness in the forefront of all clinicians’ minds. [We need to make sure] they’re reporting and suspecting AFM [and] collecting specimens as early as possible. It is a rare disease, but it’s such a severe one that we need as much information as possible so we can learn more about what may be causing this and can prevent [future cases in] other families.”
Not Related to Zika
In a CDC review, confirmed cases were defined as acute flaccid limb weakness and spinal cord gray matter lesions on MRI. A total of 311 confirmed AFM cases were reported between August 2014 and October 2016. Compared to the first cases in 2014, those confirmed in 2016 had a lower median age (5 vs. 7 years), were more likely to present with altered mental status, (26% vs. 11%), have more than two limbs affected (48% vs. 32%), and require mechanical ventilation (33% vs. 20%), Ayers and colleagues reported.1
The first cluster of AFM cases occurred in Denver in August 2014.2 Earlier in 2014, California clinicians had noted an excessive number of acute flaccid paralysis cases in children.3 The CDC issued a health advisory and began active surveillance for AFM cases on Sept. 21, 2014.
Just to clarify, the current AFM syndrome is not caused by the polio virus and it emerged before Zika, which has complicated things because it produces a similar paralytic condition called Guillain-Barré Syndrome.
“There are different parts your spinal cord [connected] to the nerve junction in your muscles that can cause paralysis,” Ayers says. “And Guillain-Barré is one where at the nerves, the demyelination happens on its way to your muscle, and you can get paralysis that way. What we’re looking at for acute flaccid myelitis, very specifically, is the infection is happening in the spinal cord.”
Another investigation at the meeting established a strong link between GBS and Zika infection in an investigation in Puerto Rico. During local Zika virus transmission in 2016, the Puerto Rico Department of Health reported 66 GBS cases with laboratory evidence of Zika infection. That essentially doubled the typical GBS annual rate of about 60 cases to 120 with the addition of the Zika-related cases.4
“It’s important to remember that Guillain-Barré is a post-infectious autoimmune disorder,” says Emilio Dirlikov, MD, the GBS team lead for the CDC’s Zika response in Puerto Rico. “It can be caused by Zika — attributed to Zika virus, but there are many other triggers, including bacteria and viruses. So, for our surveillance system, under the Zika virus response, we asked providers to report any case that had a suspicion of GBS.”
REFERENCES
- Ayers T, Lopez A, Kambhampati, A. It’s Not Polio! Acute Flaccid Myelitis — United States, August 2014–October 2016. CDC EIS Conference. Atlanta, April 24-27, 2017.
- Pastula DM, Aliabadi N, Haynes AK, et al. Acute Neurologic Illness of Unknown Etiology in Children — Colorado, August–September 2014. MMWR 2014;63(40);901-902.
- Ayscue P, Haren KV, Sheriff H, et al. Acute flaccid paralysis with anterior myelitis – California, June 2012–June 2014. MMWR 2014.63:903-906.
- Dirlikov E, Major C, Medina N, et al. Acute Zika Virus Infection as a Risk Factor for Guillain-Barré Syndrome — Puerto Rico, April–December 2016. CDC EIS Conference. Atlanta, April 24-27, 2017
