November 13, 2018
The number of US children with acute flaccid myelitis (AFM) continues to grow, and federal health officials still do not know what's triggering the polio-like paralysis characterized by sudden weakness or loss of muscle tone in the arms or legs.
As of November 13, there are a total of 90 confirmed cases of AFM across 27 states, according to the US Centers for Disease Control and Prevention (CDC). These 90 confirmed cases are among the total of 252 reports that CDC has received of patients under investigation for AFM.
The 90 confirmed cases reported today are up from 80 confirmed cases (among a total of 219 under investigation) across 25 states CDC reported 1 week earlier, on November 5.
"So far there have been no deaths among AFM patients reported to CDC in 2018," Nancy Messonnier, MD, director of CDC's National Center for Immunization and Respiratory Diseases, noted during a media briefing.
However, she acknowledged that "one of the gaps in our program is that we don't have long-term follow-up in every AFM patient and it's something that we are working to correct."
On that front, the CDC has now asked US health departments to cross-reference their list of AFM cases (from this year and prior years) against their death registries to identify any deaths that may have been the result of AFM.
Messonnier said most AFM cases involve children between 2 and 8 years old and about half are male. Almost all reported fever and/or respiratory illness in the 3 to 10 days before limb weakness. In almost all patients, an upper limb was involved. In about half, only an upper limb was involved.
"Some patients recover fully from AFM, but at least half of the patients don't recover and have really serious sequelae" and it's unclear why, she noted.
Messonnier said the CDC has tested 125 spinal cord fluid, respiratory, and stool specimens from 71 of 80 confirmed AFM cases. Of the respiratory and stool specimens tested, about half were positive for enterovirus (EV) or rhinovirus, including EV-A71 and EV- D68. The spinal cord fluid was positive in two cases. One had evidence of EV-A71 and one had evidence of EV-D68. Still, it's too early to pin the cause on one of these viruses.
"We know that most patients with AFM have fever and/or respiratory symptoms before developing AFM. However, at this time of year, many children have fever and respiratory symptoms. Most of them do not go on to develop AFM. We are working hard to figure out what the triggers are that would cause someone to develop AFM," said Messonnier.
She also cautioned that the process of confirming new AFM cases can take "a week to a few weeks" to complete, adding that the CDC is "working to expedite the process."
The CDC has increased its network of neurologists to assist with and confirm AFM cases. The agency has also established a task force of experts in multiple disciplines to develop a comprehensive research agenda to further understand why AFM affects some children and what triggers it.
"CDC is a science-driven agency. Right now, the science doesn't give us an answer," said Messonnier.
Later this week, the CDC plans to post updated considerations for clinical management of AFM that reflect the experience of clinicians treating AFM cases.
"Unfortunately, because we don't yet know the cause of all AFM cases, these considerations are not as specific as we would like," said Messonnier. "There are currently no targeted therapies or interventions with enough evidence to endorse or discourage their use. We recommend that clinicians expedite neurology and infectious disease consultations to discuss treatment and management considerations," she advised.
The CDC has been actively investigating AFM, testing specimens, and monitoring the disease since 2014, when an increase in cases was first detected. In 2014, there were 120 confirmed cases in 34 states, and in 2016, 149 confirmed cases in 39 states. Last year, there were 33 confirmed cases in 16 states.
Messonnier said it would be "premature to project how many cases we will see this year. But so far the curve from 2018 looks similar to 2016."
The CDC continues to report updated case counts every Monday afternoon on their website.
The CDC has developed a toolkit for healthcare professionals that includes information about AFM and instructions for reporting patients under investigation to the health department.