The Latent Period Before the Onset of Acute Rheumatic Fever †

John R. Paul has been interested in the latent period and the incubation period of a variety of infectious diseases because careful study of the host during these periods frequently yields important clues concerning pathogenesis. In the case of rheumatic fever, the latent period begins at the onset of symptoms of the acute group A streptococcal respiratory infection and ends at the time of development of symptoms of acute rheumatic fever. Thus, in the early phase of the latent period, the patient exhibits signs and symptoms of tonsillitis or pharyngitis, whereas in the second phase, unless a suppurative complication supervenes, the patient is asymptomatic.1 The occurrence of a latent period prior to the development of symptoms of acute rheumatic fever or acute glomerulonephritis is responsible for the suggestion that these two complications of group A streptococcal infections represent some form of altered tissue reactivity of an immunological nature."8 Ranz, Boisvert, and Spink' studied a group of patients during the latent period and suggested, on the basis of bacteriologic studies, that reinfection with a new type of streptococcus may be necessary for the development of these non-suppurative complications. In order to define the normal latent period as well as to determine the effect of reinfection during this time interval the experience at the Streptococcal Disease Laboraory was reviewed. At this facility, all patients with clinically evident streptococcal disease or acute rheumatic fever were hospitalized and studied by standard methods including bacteriologic and serologic techniques.