Possible sexual transmission of Q fever among humans.

Direct transmission of Q fever between persons who have been exposed to Coxiella burnetii and their family members has been hypothesized on the basis of the results of serological surveillance. We studied nine shepherds who were employed in Spain during the sheep shearing season. After they returned to Poland, Q fever was detected in these shepherds and their wives. The titers of serum antibodies to phase I C. burnetii antigens ranged from 0 to 64 in patients with Q fever and in their spouses, and the titer of serum antibodies to phase II antigens ranged from 0 to 1.024 in patients and their spouses. Other family members were seronegative for antibodies to C. burnetii. C. burnetii strains were isolated from urine and semen samples obtained from patients with Q fever. Attached bacteria have been detected in spermatozoal cells observed with use of scanning electron microscopy.