Assessing the long-term health impact of Q-fever in the Netherlands: a prospective cohort study started in 2007 on the largest documented Q-fever outbreak to date.

Background: Between 2007 and 2011, the Netherlands experienced the largest documented Q-fever outbreak to date with a total of 4108 notified acute Q-fever patients. Previous studies have indicated that Q-fever patients may suffer from long-lasting health effects, such as fatigue and reduced quality of life. Our study aims to determine the long-term health impact of Q-fever. It will also compare the health status of Q-fever patients with three reference groups: 1) healthy controls, 2) patients with Legionnaires' disease and 3) persons with a Q-fever infection but a-specific symptoms.

Methods/design: Two groups of Q-fever patients were included in a prospective cohort study. In the first group the onset of illness was in 2007-2008 and participation was at 12 and 48 months. In the second group the onset of illness was in 2010-2011 and participation was at 6 time intervals, from 3 to 24 months. The reference groups were included at only one time interval. The subjective health status, fatigue status and quality of life of patients will be assessed using two validated quality of life questionnaires.

Discussion: This study is the largest prospective cohort study to date that focuses on the effects of acute Q-fever. It will determine the long-term (up to 4 years) health impact of Q-fever on patients and compare this to three different reference groups so that we can present a comprehensive assessment of disease progression over time.