Clinical and subclinical variola minor in a ward outbreak

Abstract
A variola minor outbreak in a 36-bed hospital-ward comprised seven cases of overt variola after the first case. Clinical and epidemiological findings were typical, seven of the eight cases of overt variola being confirmed by virus isolation or antibody titrations. In addition, thirteen definite and seven possible instances of subclinical variola were deduced from complement-fixation or haemagglutination-inhibition tests. A discussion is made of the validity of serological criteria of variolous and vaccinial infections.