Surveillance of Rocky Mountain Spotted Fever in the United States, 1981-1983

for 2,850 (87%7) of the 3,294 cases reported in 1981-1983. Of these 2850 cases, 1375 (48%) were laboratory confirmed. Death from RMSF was more common in persons >30 years of age (case-fatality ratio of 8.4%o) than in persons <30 years (2.2%, P < .001). Fatality was also associated with failure to obtain a history of a tick bite within 14 days before onset of illness (P < .05) and with lack of treatment with tetracycline or chloramphenicol (P < .01).