[Seroprevalence of human Q fever in Switzerland]

In current practice, only serology, by the titration of anti-Coxiella burnetii antibodies, permits the diagnosis of acute or chronic Q fever. New serological techniques have also made it possible to more accurately determine the number of people in a community who have been affected by this infectious agent. We have thus been able to compare the results of 1437 specimens from the whole of Switzerland with 4009 taken in the Valais. The analysis of these sera by indirect microimmunofluorescence now shows that Q fever is much more prevalent than was generally estimated. However, these results vary greatly from one area and another, between 6.7% and 31.7% depending on the locality. Normally the lowest percentages were found in the big cities (from 9.5% to 12.2% in Berne, Geneva and Zurich) whilst the highest incidences were found in mountain regions (from 23.6% to 31.7% in the Tessin, Uri or the Valais). Regarding sex distribution, it was found that the incidence of Q fever is on average slightly lower (between 3% and 5%) in women than in men. It was also noted that the percentage of people having anti-Coxiella burnetii antibodies increases with age. The high incidence of Q fever in Switzerland is also of concern because of a severe and chronic form of this infection: endocarditis.