Paralytic vs. "nonparalytic" polio: distinction without a difference?

Nonparalytic polio (NPP) is commonly thought to be synonymous with "abortive polio," in which the poliovirus neither entered the central nervous system 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 show that neuronal lesions in the brain and spinal cord and muscle weakness were common in NPP, and epidemiologic studies document late-onset weakness and fatigue in 14% to 42% of NPP survivors. These findings indicate that clinicians should not require a history of paralytic polio, electromyographic evidence of denervation, and new muscle weakness for the diagnosis of "Postpolio Syndrome" but should be aware that NPP, and possibly even poliovirus-induced "minor illnesses," can be associated with acute central nervous system damage and late-onset muscle weakness and fatigue.