Clinical and Laboratory Variation of Virulence in Scrub Typhus

Abstract

Summary 1. Clinical data are presented on one small and 2 large outbreaks of scrub typhus which occurred in 3 different geographical locations in the SWPA and which showed variation in the severity of illness. 2. Representative strains of the causative agent, Rickettsia orientalis were isolated in white mice from cases in the 3 areas and produced typical reactions in white mice, guinea pigs and rabbits. 3. Strains isolated from cases in an outbreak with an extremely low mortality rate were less virulent for laboratory animals than strains isolated from cases in two other outbreaks with higher mortality rates.