Serological evidence that the Q fever agent (Coxiella burnetii) has spread widely among dairy cattle of Japan.

Serological examination of bovine and human sera for antibodies against Coxiella burnetti was carried out by the immunofluorescence technique. Twenty to 30% of the cows examined were antibody-positive. Sera from two veterinarians also had antibody against C. burnetii. These results suggest an increase in the number of infected cows with C. burnetii in Japan since 1954, and also imply the possibility of the prevalence of acute Q fever in the human population, which had been underestimated and undiagnosed for the last three decades.