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POLIOMYELITIS
AN ANCIENT SCOURGE, NEARLY ELIMINATED, BUT STILL LURKING IN THE SHADOWS? BY JOHN P. MAHER, MD, MPH
P
oliomyelitis (Polio) is an ancient, highly contagious disease caused by any of three serotypes of poliovirus. It is a member of the enteroviridae genus, family picornaviridae, which have an RNA genome and are acid stable, so that the three known types (PV1, PV2, and PV3) can transit the GI tract and be shed into the environment. Transmission is generally considered “oral-fecal” (via foods, liquids, direct contact, hand-to-mouth, etc.), the efficiency of which will vary slightly with the age, personal hygiene, environmental cleanliness, dose, and health status or susceptibility of the individuals involved in the transmission events. For all practical purposes, polio has been considered eradicated here in the U.S.A. Even when/if a case is imported, its further transmission is effectively prevented by the level of “herd immunity” among our general population – except of course if it would reach certain sub-population groups (e.g., Amish, Christian Scientists) who may avoid getting immunizations because of religious or deeply philosophical beliefs which constitute legal exemptions to state immunization laws/regulations. In third world countries, people may refuse vaccination due to fear, superstition, or pressure from political or religious extremist groups. So, in those settings, or where people and tribes may be extremely isolated and health programs unavailable, and since only humans are hosts to this virus, it is still conceivable that until/ unless the virus is completely eradicated there could still be a
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resurgence of paralytic polio, depending upon the world’s political, social and economic realities. From 1990 to 1999 there were 162 reported cases in the U.S., with an average of only 8 cases of wild virus polio per year reported here. Of those, six (6) were acquired outside the U.S., and two (2) were classified as “indeterminate” (meaning that no polio virus was isolated from the patients, and that they had no history of recent vaccination nor direct contact with a vaccine recipient). All of the remaining 154 (95%) cases were “vaccine-associated paralytic polio (VAPP) caused by the Sabin poliovirus strains in the oral polio vaccine” (more about this below). Because of the effectiveness of our American system of Public Health and the active participation of physicians, hospitals, parents and school systems, most Americans these days have had no real experience with epidemic or pandemic diseases with the current exception of the ongoing COVID-19 pandemic caused by the SARS CoV-2 virus. With the exception, perhaps, of the 10 Plagues on Pharoah’s Egypt which we pass over in silence (with apologies to Cicero and our old Latin teachers for the use of the praeteritio), all our combined histories would show only a handful of truly global prior pandemic diseases, namely: Plague, Yellow Fever, Malaria, Cholera, the 1918 Spanish Flu, and arguably Syphilis (or “the Great Pox”). The 1950s, when this author was a teenager, were full of fear and anxiety about polio – a disease whose cause and cure were
