Paralytic Versus "Non-Paralytic" Polio: A Distinction without a Difference?

Non-paralytic polio (NPP) is commonly thought to be synonymous with "abortive polio," in which the poliovirus neither entered the CNS nor damaged neurons. Described are two epidemic illness -"The Summer Grippe" and Iceland disease -apparently caused by a low virulence but neuropathic type 2 poliovirus, studies showing that neuronal lesions in the brain and spinal cord and muscle weakness were common in NPP, and epidemiologic studies documenting late-onset weakness and fatigue in 14% to 42% of NPP survivors. Clinicians should not require a history of paralytic polio, EMG evidence of denervation and new muscle weakness for a diagnosis of "Post-Polio Syndrome," but should be aware that NPP, and possibly even a poliovirus-induced "minor illnesses," can be associated with CNS damage and late-onset muscle weakness and fatigue.