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US sees rise in rare polio like syndrome of unknown cause

BMJ 2016; 355 doi: https://doi.org/10.1136/bmj.i5981 (Published 07 November 2016) Cite this as: BMJ 2016;355:i5981

Acute flaccid myelitis/AFM is on the rise again in the US

Acute flaccid myelitis/AFM is the polio-like syndrome that first broke out in US schoolchildren in August 2014. It seems to be following a biennial pattern with August through October peaks in 2014, 2016, and now in 2018. As of October 26 there have been 72 confirmed US cases in 2018 with another 119 suspect cases under investigation. (CDC, AFM Investigation, 10/26/18) The CDC has billed it as a "mystery disease", but some experts in pediatric infectious disease and neurology contend that existing evidence points to enteroviruses, especially EV-D68, which usually causes self-limited respiratory illness. The mystery is why a small minority develop paralytic illness, sometimes severe and apparently permanent in some cases.

The CDC has been walking a fine line between alarm and reassurance, and between knowledge and uncertainty about causation. Notes of impatience with CDC efforts have entered news reports, and some observers think that CDC advice about prevention ("stay up-to-date with vaccinations...avoid mosquito bites...hand washing") is largely irrelevant and possibly, counterproductive.

One idea that is beginning to gain traction is that intramuscular injections may be co-factors in the causation of AFM. "Provocation paralysis" is remembered by old-timers who remember the association between IM injections of vaccines and antibiotics and paralytic polio. (Hill, BMJ 1950. Mawdsley, Lancet 2014. Strebel, NEJM 1995) When muscle is damaged poliovirus receptors are up-regulated, and polioviruses can attach to motor endplates during the viremic phase of infection. Viruses can then travel retrograde along axons to the spinal cord and produce paralytic polio. (Dalakas, NEJM 1995. Gromeier. J Virol 1998). Perhaps non-polio enteroviruses can do the same thing.

The foregoing has implications for US policy regarding medical practice and vaccine mandates.

Competing interests: No competing interests

31 October 2018
Allan S. Cunningham
Retired pediatrician
Cooperstown NY 13326, USA