Importance of Q fever in community acquired pneumonia.

Coxiella burnetii appears to be endemic in animals in the Mauricie region of Quebec, and causes some human cases of Q fever annually. Unlike in other rural areas, patients in this study experienced few respiratory symptoms. To determine whether C burnetii pneumonia is underdiagnosed, adults admitted to hospital for community acquired pneumonia were included in a one-year serological study. Significant immunofluorescent antibody (IFA) titres in four of 118 patients with pneumonia (fewer than 4%) were studied. Clinical presentation, standard laboratory tests and epidemiological data did not allow identification of these cases; however, Q fever increased during the warm months. There were no detectable complement fixing (CF) antibodies in these four cases. C burnetii causes few cases of pneumonia in Mauricie. IFA seems to be a more sensitive test than CF.