THE INCIDENCE OF INFECTION AMONG CONTACTS OF POLIOMYELITIS CASES 1

Abstract

One of the epidemiological features which puzzled early students of poliomyelitis was the apparently erratic spread of the disease with rarely more than one case in a family. Subsequently, it became apparent that unlike measles among the common virus diseases, the majority of infections with poliomyelitis virus were either mild or inapparent and, therefore, went undetected. A number of epidemiological survey studies carried out during the past two decades indicated that actually a high infection rate was common among family contacts of poliomyelitis cases even though only one individual in the family became sick. Until recently, however, the laboratory methods available for studying the problem were largely limited to the isolation of virus by monkey inoculation, and the exact rates or degree of spread of this infection through families remained unknown. With the introduction of tissue culture methods into poliomyelitis research, it has been possible to carry out more extensive virological studies, and to relate virus isolation-or its absence-to the immune or antibody status of the individuals tested. The present study is concerned with poliomyelitis infection rates among close contacts of cases and indicates actually how high they may be. Tissue culture methods, which have been brought to bear on the problem, have been responsible for these results.