An epidemiologic and entomologic investigation of a cluster of Rocky Mountain spotted fever cases in Delaware.

BACKGROUND: Rocky Mountain spotted fever (RMSF) continues to be the most common fatal tick-borne illness in the United States. In August of 1996, four children attending a summer camp in Delaware were diagnosed with RMSF. This report summarizes the results of the epidemiologic and entomologic investigation conducted by the Delaware Division of Public Health and the Centers for Disease Control and Prevention regarding this cluster of RMSF cases. Epidemiologic and clinical aspects of RMSF, as well as previously reported clusters of the disease, are also reviewed. METHODS: A questionnaire regarding symptoms and activities was administered via telephone to 163 (73 percent) of the 223 attendees. A suspected case was defined as an illness in a person attending the camp between August 11 and 17 that occurred during the two-week period following the session, characterized by either 1) fever with one or more symptoms (i.e., headache, rash, myalgia, or fatigue) or 2) no fever with two or more symptoms. Cases of RMSF were confirmed by serologic evaluation. RESULTS: Seven of 13 patients with suspected RMSF submitted sera for testing. Four patients had confirmed RMSF; three were males, and the median age was 12.5 years compared with 12 years for all attendees. All confirmed patients reported fever, headache, fatigue, and rash. An increased risk of becoming ill was associated with overnight camping at site A (Odds Ratio (OR) undefined, p = 0.02), visiting or overnight camping at site B (OR undefined, p = 0.003 and 0.002), and leaving the trails when hiking (OR undefined, p = 0.02). CONCLUSIONS: These data suggest that development of RMSF was associated with visiting or camping at specific sites and behavior likely to increase contact with ticks. Camp supervisors were advised to educate campers regarding tick bite prevention measures, reduce underbrush around campsites, and encourage campers to remain on the trails. Health care providers should remain aware of the increased risk for RMSF during the spring, summer, and fall months.

The epidemiology of Lyme disease in Delaware 1989-1992.

OBJECTIVES: The study was conducted to describe the temporal, geographic, demographic and treatment characteristics of Lyme disease in Delaware and to assist health planners in developing and implementing control strategies. METHODS: All physician-submitted Centers for Disease Control and Prevention (CDC) follow-up Lyme disease report forms from 1989 through 1992 were reviewed for completeness. Data were gathered from completed forms only. All cases were classified according to the 1990 CDC surveillance case definition. Cases were further subdivided into two groups. Antibiotic usage patterns were then identified for each group. Data on the percentage of infected ticks by county were obtained from a 1988 study conducted by the University of Delaware; Delaware Health and Social Services, Division of Public Health; and the Department of Natural Resources and Environmental Control. RESULTS: Reported cases of Lyme disease increased 246 percent between 1989 and 1992. The 1992 statewide incidence rate was 12.6 cases per 100,000 population. Whites were four times more likely to contract Lyme disease than were blacks. The majority of cases were reported between June and October. The number of patients being treated with oral antibiotics for localized disease for three weeks or longer increased from 52 percent in 1991 to 94 percent in 1992. Ixodid ticks infected with Borrelia burgdorferi were found in all three counties. CONCLUSION: The Delaware State Board of Health made Lyme disease reportable in September 1989. This requirement increased the quality of Lyme disease surveillance; however, the disease is probably under-reported since Delaware does not actively solicit Lyme disease reports. Delaware's case data reflect national data which indicate an increase in reported cases. A trend toward longer duration of treatment for localized Lyme disease is evident.