Epidemiology of Poliomyelitis and Allied Diseases, 1963 †**

A striking feature of paralytic poliomyelitis has been its ever changing epidemiology. In the past, changes seem to have come about in the course of natural evolution from an endemic to an epidemic pattern, first in one part of the world, and then in another. At present, the use of effective vaccines for prevention and for greatly reducing circulation of wild strains of the virus, have apparently had a real impact on the epidemiological behavior of the disease and we can perhaps anticipate further shifts, not only in connection with polioviruses, but with other members of the enterovirus family, some of which are capable of inducing poliomyelitis-like illnesses. These latter are assuming increased significance, for as the rates of true paralytic poliomyelitis decline, poliomyelitis-like illnesses assume greater relative importance.