A sero-epidemiological survey of asymptomatic cases of Boutonneuse fever in western Sicily.

963 sera from contacts, persons from various localities, and blood donors were examined with a commercially produced kit for micro-immunofluorescence for the presence of antibodies to Rickettsia conorii. 10.6% of sera were serologically positive. The higher rates of positivity were observed in sera of contacts (19%) and persons from Mussomeli (20%) and Ustica (18.4%), the lower rates in blood donors from Palermo (3.5%). These results support the view that there is an occupational risk factor related to a rural environment.