In 1988, state health departments reported 615 cases of Rocky Mountain spotted fever (RMSF) to CDC, an increase of 3.9% from the 592 cases reported in 1987. The incidence was 0.3 per 100,000. Of the 615 cases, 200 (32.5% ) were reported from the South Atlantic region and 149 (24.2%) from the West South Central region. Oklahoma had the highest rate (97 cases, 3.0 per 100,000); other states with high rates were North Carolina (108 cases, 1.7 per 100,000), Arkansas (32 cases, 1.3 per 100,000), Missouri (57 cases, 1.1 per 100,000), and Kansas (26 cases, 1.0 per 100,000) (Figure 1).
Detailed case report forms were submitted on 555 (90.2% ) of the 615 cases. Of these, 362 (65.2% ) were laboratoryconfirmed*, 31 (5.6%) were classified as probable†, and 162 (29.2% ) were not conformed. Males accounted for 63.8% cases; onset of symptoms occurred between April 1 and July 31 in 81.2%, and a tick