US doctors criticise CDC’s response to “mystery” polio-like disease in childrenBMJ 2018; 363 doi: https://doi.org/10.1136/bmj.k4633 (Published 01 November 2018) Cite this as: BMJ 2018;363:k4633
An unexplained polio-like illness that spikes in frequency every second year seems to be on course for a new record number of cases.
The US Centers for Disease Control and Prevention (CDC) first publicised its concern about acute flaccid myelitis (AFM) two weeks ago, since which time the number of cases reported this year has climbed from 127 (62 confirmed) to 191 (72 confirmed).1 Cases have been confirmed in 24 states.
Canada also last week reported a sudden September spike in cases, raising the year’s total from fewer than five reported cases to 30.
Meanwhile, several doctors treating the disease, including four who advise the CDC on it, have criticised the agency’s response and its use of the word “mystery,” arguing that the evidence is enough to at least work on the assumption that AFM is often caused by the common enterovirus D68.
AFM has spiked sharply in the September of each of the past three even numbered years since the CDC began tracking it in 2014. In 2015 and 2017, by contrast, cases were only about a fifth as frequent, with no late summer spike.
Evidence also shows that a smaller spike occurred in 2012. To date, no one has proposed a mechanism that could explain this 24 month cycle. For at least six years, the data suggest, each trough and wave of AFM has been a little greater than the one that preceded it.
The onset of AFM is like polio, with flu or pneumonia symptoms followed by sudden weakness in the limbs. Nine in 10 cases occur in children, and the average age is 4 years. Some patients eventually regain the use of their limbs after extensive physical therapy, but recovery is not guaranteed.
“This is generally a pretty dramatic disease,” said Nancy Messonnier, director of the National Center for Immunization and Respiratory Diseases, announcing this year’s spike. “There is a lot we don’t know about AFM, and I am frustrated that despite all of our efforts, we haven’t been able to identify the cause of this mystery illness.”
Poliovirus itself has been eliminated as a cause, she said, but no single pathogen has consistently shown up in patients’ spinal fluid. Poliovirus also often did not show up in spinal fluid when it was paralysing people decades ago.
The CDC’s caution in attributing the cause has been heavily criticised by neurologists and paediatric infectious disease specialists treating the disease. Three have expressed their frustrations to the Los Angeles Times,2 and four of the CDC’s own medical advisers on AFM condemned the agency’s response in comments to CNN.3
Kenneth Tyler, a professor of neurology at the University of Colorado, told CNN, “This is the CDC’s job. This is what they’re supposed to do well. And it’s a source of frustration to many of us that they’re apparently not doing these things.”
The common message from these doctors was that it is time to focus on enteroviruses—although in a Colorado cluster of cases it has been linked to enterovirus A71 rather than D684—and that it is unreasonable to expect that the pathogen will be detectable every time, as most doctors believe that the myelitis is caused by an immune response that continues after the virus is cleared.
Also speaking to CNN were a group of mothers who complained that warnings about AFM were not reaching emergency rooms. Children with sudden paralysis were still being sent home by doctors who attributed their symptoms to pinched nerves, the mothers said.
Messonnier responded to CNN, “If this virus was causing this damage, we’d expect to be able to find the virus in the spinal fluid of most of these patients, and we’re not. We cannot explain these three peaks of disease in [2014, 2016, and 2018] by enterovirus, and so in the way that any discriminating scientist would do, we’re trying to think more broadly and make sure that we’re not missing something.”