Cat scratch disease in the United States: an analysis of three national databases.

Objectives: Current knowledge of the epidemiology of cat scratch disease is based primarily on information from case series. We used three national databases to obtain more representative data to determine the incidence and demographics of cat scratch disease.

Methods: Records coded with the diagnosis of cat scratch disease from two hospital discharge databases and an ambulatory care database were analyzed. Costs of diagnostic tests and hospitalization were obtained from a sample of providers and published data.

Results: The incidence of patients discharged from hospitals with a diagnosis of cat scratch disease was between 0.77 and 0.86 per 100,000 population per year. Fifty-five percent of the case patients were 18 years of age or younger. Males accounted for 60% of cases. Incidence varied by season; approximately 60% of case patients were discharged in the months September through January. The estimated incidence of disease in ambulatory patients was 9.3 per 100,000 population per year. On the basis of these rates, we estimated the annual health care cost of the disease to be more than $12 million.

Conclusions: The rates and seasonality of cat scratch disease found in this study were consistent with previous reports. Adults represented a higher percentage of the total than reported in previous case series, suggesting that the disease may affect more adults than previously recognized.