Acute Flaccid Paralysis and Enteroviral Infections

The focus of this review is on enterovirus (EV)-associated acute flaccid paralysis (AFP) due to spinal cord anterior horn cell disease. Emphasis is placed on the epidemiology, pathogenesis, diagnosis, treatment, and outcome of AFP caused by polioviruses, vaccine-derived polioviruses, EV-D68, and EV-A71.

Since the launch of The Global Polio Eradication Initiative in 1988, the worldwide incidence of polio has been reduced by 99.9%, with small numbers of poliomyelitis cases being reported only in Afghanistan, Pakistan, and Nigeria. With the planned phaseout of oral polio vaccine, vaccine-associated poliomyelitis is also expected to be eliminated. In their place, other EVs, chiefly EV-D68 and EV-A71, have emerged as the principal causes of AFP. There is evidence that the emergence of EV-D68 as a cause of severe respiratory disease and AFP was due to recent genetic virus evolution. Antiviral medications targeting EV-D68, EV-A71, and other EVs will likely be available in the near future. An effective EV-A71 vaccine has been developed, and preliminary investigations suggest an EV-D68 vaccine could be on the horizon. The eradication of poliomyelitis and vaccine-associated poliomyelitis is near, after which other EVs, presently EV-D68 and EV-A71, will be the principle viral causes of AFP. Moving forward, it is essential that EV outbreaks, in particular those associated with neurologic complications, be investigated carefully and the causal strains identified, so that treatment and prevention efforts can be rapidly developed and implemented.