The Centers for Disease Control and Prevention (CDC) is investigating a national increase in acute flaccid myelitis (AFM) this year, with a surge in recent months, a pattern that may be linked to a recent cluster of suspected cases in Washington state.
Though this year's cases of AFM—marked by sudden onset of limb weakness associated with spinal cord inflammation—haven't reached levels seen in 2014 when the condition first appeared on the national radar with 120 cases reported, the CDC said it is worried about the recent uptick.
No common cause identified
In an update on its AFM page yesterday, the CDC said as of Sep 30, 89 AFM cases have been confirmed in 33 states, mostly in children. The rise in cases from across the country began in August, and the CDC said it has been actively investigating the illness since then.
For comparison, in 2015 the agency received reports of 21 confirmed AFM cases from 16 states.
Despite extensive testing, the CDC hasn't yet determined what's causing the AFM cases. A long list of viruses can cause AFM symptoms, including poliovirus and adenoviruses. The 2014 outbreak coincided with a national outbreak of severe respiratory illnesses caused by enterovirus D68 (EV-D68).
CDC scientists have tested many specimens from patients, but so far they haven't consistently detected a pathogen in spinal fluid, which it said would likely yield good evidence about the cause, given that the illness affects the spinal cord.
The CDC said it's hard to sort out trends with AFM data, because reporting began only in 2014 and is voluntary for most states. Initial years of reporting might contain data variability that makes it hard to compare cases from year to year. "One possible reason for differences in annual reporting is more awareness among and reporting by healthcare providers and health departments," it said.
Washington's cluster rises to 9
Meanwhile, the Washington State Department of Health (WSDH) said in an Oct 28 media statement that it is leading a joint investigation that includes the CDC into a cluster of eight suspected AFM cases, all of them involving children admitted to Seattle Children's Hospital with acute neurologic illness.
The children are from four counties: King (3), Pierce (1), Franklin (2), and Whatcom (2). They were admitted with a range of types and severity of symptoms, ranging in age from 3 to 14 years. Three are still hospitalized, and five have been released.
Yesterday the Seattle Times reported one more patient, a child from Snohomish County who is hospitalized. The report said one child, a 6-year-old boy, has died, and it cited a CDC official who said two of the cases have been confirmed as AFM.
Scott Lindquist, MD, MPH, state infectious disease epidemiologist, said in the WSDH release that so far evidence doesn't point to a single illness source among the cases. "However, this investigation is just getting underway and we're looking at all possibilities as we try to understand what might have contributed to these illnesses."
Washington had two AFM cases in 2014 and none in 2015, according to the WSDH.
Nov 1 CDC AFM page
Oct 28 WSDH press release
Nov 1 Seattle Times story