Characteristics of hospitalized acute Q fever patients during a large epidemic, The Netherlands.

Background: From 2007 to 2009, The Netherlands experienced a major Q fever epidemic, with higher hospitalization rates than the 2-5% reported in the literature for acute Q fever pneumonia and hepatitis. We describe epidemiological and clinical features of hospitalized acute Q fever patients and compared patients presenting with Q fever pneumonia with patients admitted for other forms of community-acquired pneumonia (CAP). We also examined whether proximity to infected ruminant farms was a risk factor for hospitalization.

Methods: A retrospective cohort study was conducted for all patients diagnosed and hospitalized with acute Q fever between 2007 and 2009 in one general hospital situated in the high incidence area in the south of The Netherlands. Pneumonia severity scores (PSI and CURB-65) of acute Q fever pneumonia patients (defined as infiltrate on a chest x-ray) were compared with data from CAP patients. Hepatitis was defined as a >twofold the reference value for alanine aminotransferase and for bilirubin.

Results: Among the 183 hospitalized acute Q fever patients, 86.0% had pneumonia. Elevated liver enzymes (alanine aminotransferase) were found in 32.3% of patients, although hepatitis was not observed in any of them. The most frequent clinical signs upon presentation were fever, cough and dyspnoea. The median duration of admission was five days. Acute Q fever pneumonia patients were younger, had less co-morbidity, and lower PSI and CURB-65 scores than other CAP patients. Anecdotal information from attending physicians suggests that some patients were admitted because of severe subjective dyspnoea, which was not included in the scoring systems. Proximity to an infected ruminant farm was not associated with hospitalization.

Conclusion: Hospitalized Dutch acute Q fever patients mostly presented with fever and pneumonia. Patients with acute Q fever pneumonia were hospitalized despite low PSI and CURB-65 scores, presumably because subjective dyspnoea was not included in the scoring systems.