Fatigue following acute Q-fever was first described in 1960 [
68]. Without indicating a time-relation with acute Q-fever, it was noted in 1990 that 4% of acute Q-fever cases had prolonged fatigue [
53]. In 1992, it was stated that approximately 23% of study subjects developed QFS within 12 months following acute Q-fever [
44]. Ever since, several studies on fatigue following acute Q-fever reported different prevalences. It was stated that 5–10% of patients experience residual asthenia six months after acute Q-fever and only few after one year [
38]. In a reaction, it was underlined that a substantial proportion of acute Q-fever patients have symptoms similar to QFS for 6–9 months after the acute infection and then recover, but 8–10% of patients exhibit symptoms for at least a year [
33]. This is similar to other reports, showing persistent symptoms for longer than two years [
3], up to six years after the infection with 66% of patients reporting fatigue [
14]. In Australia, QFS is the most common sequel of acute Q-fever reported to affect 10–15% of patients [
70]. Higher percentages were described, with up to 28% of patients meeting the Centres for Disease Control and Prevention criteria for CFS 5 to 14 years after acute Q-fever, compared to none in the control group [
8,
15]. The highest percentage of reported fatigue was 69% five years after acute Q-fever [
9]. CFS criteria were met by 42% of C. burnetii-infected patients and 26% of controls [
9,
15]. Ten years after acute Q-fever, 68% of patients reported fatigue of any duration [
54], of whom 20% met the CFS criteria [
15]. Excluding co-morbidity, 8% of patients met the CFS criteria compared to none of the controls [
54]. C. burnetii-exposed compared to non-exposed subjects reported ten years later a fatigue prevalence of 65% vs. 35%, respectively, and 19% vs. 4% met the CFS criteria [
7,
15]. In accordance, later results demonstrated fatigue to be more common after Q-fever compared to controls [
58], up to two [
61] and six years later [
49,
69].
12]. And, although not significantly different, 12 months after acute Q-fever, patients were more fatigued than after Legionnaires’ disease, while being younger and having less pre-existing health problems [
11]. In patients with a lower respiratory tract infection who were C. burnetii seropositive 10–19 months after the acute illness, 40% reported clinically relevant fatigue, compared to 64% of seronegatives, concluding that patients have long-term health problems after a lower respiratory tract infection in general [
64].
In conclusion, fatigue following acute Q-fever might not be specific but occurs frequently and may persist for years. A large variance in prevalence of fatigue after Q-fever is reported between countries, due to differences in definitions, study designs and populations, and measurement tools, which impairs direct comparisons.
...In conclusion, there are clear indications that fatigue following acute Q-fever results in a high burden of disease, a major negative impact on the health status of patients, and has significant economic implications.
