To determine previous exposure and incidence of
rickettsial infections in western Kenya during 2007–2010,
we conducted hospital-based surveillance. Antibodies
against rickettsiae were detected in 57.4% of previously
collected serum samples. In a 2008–2010 prospective
study, Rickettsia felis DNA was 2.2× more likely to be
detected in febrile than in afebrile persons.