Brucellosis in a group of travelers to Spain.

An epidemiologic investigation, initiated when Brucella melitensis infection was detected in a high school student, identified five unrecognized cases in classmates. Before the investigation, four infected students had symptoms of brucellosis for one to ten weeks, made nine visits to physicians, and were confined to the school infirmary or hospitals for 27 days. The other two students were asymptomatic when Brucella agglutination testing demonstrated elevated titers, and treatment was quickly instituted when symptoms occurred. Travel to Spain was implicated because cases were clustered in six of 27 travelers compared with none of 23 control students. Food-history questionnaires showed more frequent consumption of cheese by infected than noninfected travelers. This cluster of cases demonstrates the risk of brucellosis in travelers to endemic areas and illustrates the value of an epidemiologic investigation of cases.