An Egyptian stele dating from c.1500 BC describes a flaccid paralysis characteristic of poliovirus infection. It was not until the 1800s, however, that polio emerged as an important infection. The German physician Jakob Heine provided the first modern description in 1840. By the late 19th century, sporadic outbreaks of poliomyelitis had begun to occur world-wide. In 1890, Swedish physician Oskar Medin described the contagious nature of poliomyelitis and its epidemic potential.1 The first large epidemic in the United States was in 1905, with more than 3000 cases. In 1910, more than 7000 US cases were recorded, and in 1916 the country was shocked by more than 29,000 cases (the most severe US epidemic of polio on record). Wade Hampton Frost provided the first comprehensive description of the epidemiology of poliomyelitis in 1913, in a classic monograph, Bulletin No. 90, “Epidemiologic Studies of Acute Anterior Poliomyelitis.”2
Frost began his studies of polio in 1910, and in the next 3 years personally investigated 6 outbreaks with a total of 475 paralytic cases and another 54 cases in which central nervous system problems failed to develop (“abortive poliomyelitis,” in the lexicon of the day). Two of these outbreaks were in large cities, 2 were in small towns, and 2 were in rural areas. This diversity of settings helped Frost to make epidemiologic inferences.
His report provided 2 key observations. One, persons who are exposed to the virus have a low risk of contracting the disease (demonstrated by a secondary attack rate of less than 3% within the families of an affected person). Two, the infectious agent has a wide distribution (at least during epidemic periods), conferring immunity on most of the population while producing disease in only a few. Frost described his logic as follows: “The spontaneous decline of epidemics in localities where only a small percentage of the people have been attacked...suggests that a population may be immunized by an epidemic giving rise to only one recognized case of poliomyelitis among... several thousand inhabitants.”2 In this observation, Frost introduced the indispensible concept of the “passive (healthy) carrier.”
1. Paul SR. A History of Poliomyelitis.
New Haven, CT: Yale University Press; 1971.
2. Frost WH. Epidemiologic Studies of Acute Anterior Poliomyelitis: (1) Poliomyelitis in Iowa, 1910. (2) Poliomyelitis in Cincinnati, 1911. (3) Poliomyelitis in Buffalo and Batavia, NY, 1912.
Washington, DC: Hygienic Laboratory; 1913. Bulletin No. 90.