Rocky Mountain spotted fever (RMSF) is the most commonly reported fatal tick-borne disease in the United States. During 1997-2002, 3,649 cases of RMSF were reported to the Centers for Disease Control and Prevention via the National Electronic Telecommunications System for Surveillance; 2,589 case report forms, providing supplemental information, were also submitted. The average annual RMSF incidence during 1997-2002 was 2.2 cases/million persons. The annual incidence increased during 1997-2002 to a rate of 3.8 cases/million persons in 2002. The incidence was lowest among persons aged<5 and 10-29 years, and highest among adults aged 60-69 years. The overall case-fatality rate was 1.4%; the rate peaked in 1998 at 2.9% and declined to 0.7% in 2001 and 2002. Children<5 years of age had a case-fatality rate (5%) that was significantly greater than the rates for age groups<60 years of age, except for that for 40-49 years of age. Continued national surveillance is needed to assess the effectiveness of prevention efforts and early treatment in decreasing severe morbidity and mortality associated with RMSF.

The increased incidence of Rocky Mountain spotted fever (RMSF) in 1997-2002 compared with previous years may be related to enhanced awareness and reporting of RMSF as well as changes in human-vector interaction. However, reports on RMSF mortality underscore the need for physician vigilance in considering a diagnosis of RMSF for febrile individuals potentially exposed to ticks and stress the importance of treating such persons regardless of the presence of a rash.