Poliomyelitis in Laos, 1962–1963: Epidemic and immunity survey

Abstract

A poliomyelitis outbreak occurred among young children in Laos between October, 1962, and March, 1963. These children lived in towns in which no sanitary improvements or changes in pattern of life had been made. Postepidemic immunity studies suggested that polioviruses had been spreading extensively and that paralytic polio type 1 occurred at epidemic proportions in a population which normally might be expected to have a low incidence of paralytic disease. The occurrence and virulence of the 1962–1963 Laos outbreak can perhaps be explained by changes in the virulence of the prevalent polioviruses.