A randomised controlled trial testing the efficacy of Fit after COVID, a cognitive behavioural therapy targeting severe post-infectious fatigue following COVID-19 (ReCOVer): study protocol.

BACKGROUND: Coronavirus disease 2019 (COVID-19) results in debilitating long-term symptoms, often referred to as Post-Acute Sequelae of SARS-CoV-2 Infection (PASC), in a substantial subgroup of patients. One of the most prevalent symptoms following COVID-19 is severe fatigue. Prompt delivery of cognitive behavioural therapy (CBT), an evidence-based treatment that has shown benefit in reducing severe fatigue in other conditions, may reduce post-COVID-19 fatigue. Based on an existing CBT protocol, a blended intervention of 17 weeks, Fit after COVID, was developed to treat severe fatigue after the acute phase of infection with SARS-CoV-2. METHOD: The ReCOVer study is a multicentre 2-arm randomised controlled trial (RCT) to test the efficacy of Fit after COVID on severe post-infectious fatigue. Participants are eligible if they report severe fatigue 3 up to and including 12 months following COVID-19. One hundred and fourteen participants will be randomised to either Fit after COVID or care as usual (ratio 1:1). The primary outcome, the fatigue severity subscale of the Checklist Individual Strength (CIS-fatigue), is assessed in both groups before randomisation (T0), directly post CBT or following care as usual (T1), and at follow-up 6 months after the second assessment (T2). In addition, a long-term follow-up (T3), 12 months after the second assessment, is performed in the CBT group only. The primary objective is to investigate whether CBT will lead to a significantly lower mean fatigue severity score measured with the CIS-fatigue across the first two follow-up assessments (T1 and T2) as compared to care as usual. Secondary objectives are to determine the proportion of participants no longer being severely fatigued (operationalised in different ways) at T1 and T2 and to investigate changes in physical and social functioning, in the number and severity of somatic symptoms and in problems concentrating across T1 and T2. DISCUSSION: This is the first trial testing a cognitive behavioural intervention targeting severe fatigue after COVID-19. If Fit after COVID is effective in reducing fatigue severity following COVID-19, this intervention could contribute to alleviating the long-term health consequences of COVID-19 by relieving one of its most prevalent and distressing long-term symptoms. TRIAL REGISTRATION: Netherlands Trial Register NL8947 . Registered on 14 October 2020.

Impact of Q-fever fatigue syndrome on patients' work status.

BACKGROUND: Chronic illnesses can increase the risk of unemployment, but evidence on the specific impact of Q-fever fatigue syndrome (QFS) on work is lacking. AIMS: The aim of this study was to describe and quantify the impact of QFS on work. METHODS: Changes in work status from 1 year prior to 4 years after acute Q-fever infection of QFS patients were retrospectively collected with a self-report questionnaire measuring employment status and hours of paid work per week. In addition, information on work ability, job satisfaction and need for recovery after work was collected in 2016. Data were compared to participants from the general population. RESULTS: The proportion of employed QFS patients from 1 year prior to 4 years after acute infection decreased from 78 to 41%, while remaining relatively constant in the general population (82 to 78%). Working QFS patients showed a decrease in mean hours of paid work from 35 to 22 h per week, which is significantly steeper compared to the general population (31-28 h per week) (P < 0.001). QFS patients showed a significantly lower work ability (P < 0.001), lower job satisfaction (P = 0.006) and greater need for recovery (P < 0.001) compared to the general population. CONCLUSIONS: The number of QFS patients with paid work decreased over the years, while patients who continue to work experience lower work ability, job satisfaction and increased need for recovery. Occupational physicians should be aware of the occurrence and severity of the impact of QFS on work, even after many years.

Single nucleotide polymorphism (SNP) rs3751143 in P2RX7 is associated with therapy failure in chronic Q fever while rs7125062 in MMP1 is associated with fewer complications.

OBJECTIVES: Chronic Q fever is a persistent infection with the intracellular bacterium Coxiella burnetii. Development of chronic Q fever is associated with single nucleotide polymorphisms (SNPs) in genes encoding for pattern recognition receptors, for phagolysosomal pathway components and for matrix metalloproteinases (MMPs). We evaluated the association of SNPs in these innate-immunity and MMP genes with clinical outcomes. METHODS: SNPs were selected from previous association studies and analysed in a cohort of patients with chronic Q fever. The primary outcome was all-cause mortality; secondary outcomes were therapy failure and chronic Q fever-related complications. Subdistribution hazard ratios (SHR) were calculated. RESULTS: Nineteen SNPs were analysed in 134 patients with proven and 29 with probable chronic Q fever. In multivariable analysis, none of the selected SNPs was associated with all-cause mortality. However, SNP rs3751143 located in P2RX7 appeared to be associated with therapy failure (SHR 2.42; 95% confidence interval, 1.16-5.05; p 0.02), which is in line with other reports, showing that a loss of function of the P2X7 receptor leads to inefficient killing of intracellular organisms. In addition, SNP rs7125062 located in MMP1, involved in the cleavage of extracellular matrix, was associated with fewer chronic Q fever-related complications such as acute aneurysms (SHR 0.49; 95% confidence interval, 0.29-0.83; p 0.008). CONCLUSIONS: A polymorphism in P2RX7, known to lead to loss of function of the receptor and inefficient killing of intracellular organisms, and a polymorphism in MMP1 were respectively associated with more therapy failures and fewer complications such as acute aneurysms in patients with chronic Q fever.

[Revision of guideline on Q fever fatigue syndrome (QFS)]. / Herziene richtlijn Q-koortsvermoeidheidssyndroom (QVS).

In 2012 the multidisciplinary guideline Q fever fatigue syndrome was developed for the Netherlands. The availability of new research data and developments and experiences from daily clinical practice made it necessary to revise this guideline. The multidisciplinary working group that has revised the guideline is composed of representatives from all medical professions involved in the care of patients with QFS and representatives of the patients' association. The revised guideline incorporates a number of changes, including refinement of the QFS diagnostic criteria and updates regarding advice on support and reintegration.

Surveillance-embedded genomic outbreak resolution of methicillin-susceptible Staphylococcus aureus in a neonatal intensive care unit.

We observed an increase in methicillin-susceptible Staphylococcus aureus (MSSA) infections at a Dutch neonatal intensive care unit. Weekly neonatal MSSA carriage surveillance and cross-sectional screenings of health care workers (HCWs) were available for outbreak tracing. Traditional clustering of MSSA isolates by spa typing and Multiple-Locus Variable number tandem repeat Analysis (MLVA) suggested that nosocomial transmission had contributed to the infections. We investigated whether whole-genome sequencing (WGS) of MSSA surveillance would provide additional evidence for transmission. MSSA isolates from neonatal infections, carriage surveillance, and HCWs were subjected to WGS and bioinformatic analysis for identification and localization of high-quality single nucleotide polymorphisms, and in-depth analysis of subsets of isolates. By measuring the genetic diversity in background surveillance, we defined transmission-level relatedness and identified isolates that had been unjustly assigned to clusters based on MLVA, while spa typing was concordant but of insufficient resolution. Detailing particular subsets of isolates provided evidence that HCWs were involved in multiple outbreaks, yet it alleviated concerns about one particular HCW. The improved resolution and accuracy of genomic outbreak analyses substantially altered the view on outbreaks, along with apposite measures. Therefore, inclusion of the circulating background population has the potential to overcome current issues in genomic outbreak inference.

Genetic variations in innate immunity genes affect response to Coxiella burnetii and are associated with susceptibility to chronic Q fever.

OBJECTIVES: Chronic Q fever is a persistent infection, mostly of aortic aneurysms, vascular prostheses or damaged heart valves, caused by the intracellular bacterium Coxiella burnetii. Only a fraction of C. burnetii-infected individuals at risk develop chronic Q fever. In these individuals, a defective innate immune response may contribute to the development of chronic Q fever. We assessed whether genetic variations in genes involved in the killing machinery for C. burnetii by macrophages, contribute to the progression to chronic Q fever. METHODS: The prevalence of 66 single nucleotide polymorphisms (SNPs) in 31 genes pivotal in phagolysosomal maturation, bacterial killing and autophagy, was determined in 173 chronic Q fever patients and 184 controls with risk factors for chronic Q fever and serological evidence of a C. burnetii infection. Associations were detected with univariate logistic regression models. To assess the effect of these SNPs on innate responses to C. burnetii, the C. burnetii-induced cytokine production and basal reactive oxygen species production of healthy volunteers was determined. RESULTS: RAB7A (rs13081864) and P2RX7 loss-of-function SNP (rs3751143) were more common in chronic Q fever patients than in controls. RAB5A (rs8682), P2RX7 gain-of-function SNP (rs1718119), MAP1LC3A (rs1040747) and ATG5 (rs2245214) were more common in controls. In healthy volunteers, RAB7A (rs13081864) and MAP1LC3A (rs1040747) influenced the C. burnetii-induced cytokine production. RAB7A (rs13081864) modulated basal reactive oxygen species production. CONCLUSIONS: RAB7A (rs13081864) and P2RX7 (rs3751143) are associated with the development of chronic Q fever, whereas RAB5A (rs8682), P2RX7 (rs1718119), MAP1LC3A (rs1040747) and ATG5 (rs2245214) may have protective effects.

Chronic Q fever-related complications and mortality: data from a nationwide cohort.

OBJECTIVES: Chronic infection with Coxiella burnetii (chronic Q fever) can cause life-threatening conditions such as endocarditis, infected vascular prostheses, and infected arterial aneurysms. We aimed to assess prognosis of chronic Q fever patients in terms of complications and mortality. METHODS: A large cohort of chronic Q fever patients was assessed to describe complications, overall mortality and chronic Q fever-related mortality. Chronic Q fever-related mortality was expressed as a case fatality rate (number of chronic Q fever-related deaths/number of chronic Q fever patients). RESULTS: Complications occurred in 166 of 439 (38%) chronic Q fever patients: in 61% of proven (153/249), 15% of probable (11/74), and 2% of possible chronic Q fever patients (2/116). Most frequently observed complications were acute aneurysms (14%), heart failure (13%), and non-cardiac abscesses (10%). Overall mortality was 38% (94/249) for proven chronic Q fever patients (median follow-up 3.6 years) and 22% (16/74) for probable chronic Q fever patients (median follow-up 4.7 years). The case fatality rate was 25% for proven (63/249) chronic Q fever patients and 4% for probable (3/74) chronic Q fever patients. Overall survival was significantly lower in patients with complications, compared to those without complications (p <0.001). CONCLUSIONS: In chronic Q fever patients, complications occur frequently and contribute to the mortality rate. Patients with proven chronic Q fever have the highest risk of complications and chronic Q fever-related mortality. Prognosis for patients with possible chronic Q fever is favourable in terms of complications and mortality.

Chronic Q fever: patient and treatment-related factors influencing long-term quality of life.

BACKGROUND: Chronic Q fever is accompanied by high mortality and morbidity, and requires prolonged antibiotic treatment. Little is known on long-term quality of life (LQOL) in chronic Q fever patients treated with antibiotics. AIM: To identify patient and treatment-related factors associated with impaired LQOL in chronic Q fever patients treated with antibiotics, and to assess patients' perception on treatment. DESIGN: Cross-sectional study. METHODS: LQOL was assessed with a validated questionnaire from the Nijmegen Clinical Screening Instrument. Patients' perception on treatment was measured with three newly developed questions. RESULTS: We included 64 patients: LQOL was impaired in 55% (n = 35) after a median follow-up of 5 years. Median treatment duration was 27 months. In multivariable analysis, treatment duration was significantly associated with impaired LQOL (OR 1.07; 95%CI 1.02-1.12, P < 0.01 per month increase). Age, gender, number of antibiotic regimens, surgical intervention, complications, diagnostic classification, focus of infection or registration of side effects during treatment were not associated with impaired LQOL. After start of treatment, 17 patients (27%) perceived improvement of their condition. Disadvantages of treatment were experienced on a daily basis by 24 patients (69%) with impaired LQOL and 13 patients (46%) without impaired LQOL (P = 0.04). CONCLUSIONS: LQOL in chronic Q fever patients treated with antibiotics is impaired in more than half of patients 5 years after diagnosis. Antibiotic treatment duration was the only variable associated with impaired LQOL. The majority of patients experienced disadvantages on a daily basis, highlighting the high burden of disease and treatment.

Residents' readiness for out-of-hours service: a Dutch national survey.

BACKGROUND: Residents play a crucial role in out-of-hours service. Their perceived readiness for out-of-hours service, however, remains underexposed. This national exploratory study assesses whether or not Dutch residents feel sufficiently prepared to provide out-of-hours service at the time of their first shift, and aims to identify factors influencing perceived readiness. METHODS: An online questionnaire focussing on residents' working conditions was accessible from 21 September to 10 November 2015. Questions targeting perceived readiness for out-of-hours service were presented to all responding medical residents actively involved in out-of-hours service. Residents who felt sufficiently prepared were compared with residents who did not, exploring both individual characteristics and environmental factors. RESULTS: A total of 960 residents (mean age 32.5 years ±; 3.5, 72.4% female) from over 30 different medical specialties were included. Thirty-six percent of responding residents felt insufficiently prepared to provide out-of-hours service at the time of their first shift. Current junior status (p = 0.020), prolonged clinical experience prior to the first shift (p < 0.001), targeted training (p < 0.001), assessment of relevant skills and competencies (p < 0.001), and formal consequences following negative assessment (p = 0.001) were positively associated with perceived readiness. CONCLUSION: One-third of responding residents felt insufficiently prepared for their first out-of-hours shift. Our results emphasise the need for sufficient time to gain clinical experience as a new graduate, and underline the positive contribution of targeted training and assessment of skills and competencies relevant to out-of-hours service.

The effect of measuring serum doxycycline concentrations on clinical outcomes during treatment of chronic Q fever.

Background: First choice treatment for chronic Q fever is doxycycline plus hydroxychloroquine. Serum doxycycline concentration (SDC) >5 µg/mL has been associated with a favourable serological response, but the effect on clinical outcomes is unknown. Objectives: To assess the effect of measuring SDC during treatment of chronic Q fever on clinical outcomes. Methods: We performed a retrospective cohort study, to assess the effect of measuring SDC on clinical outcomes in patients treated with doxycycline and hydroxychloroquine for chronic Q fever. Primary outcome was the first disease-related event (new complication or chronic Q fever-related mortality); secondary outcomes were all-cause mortality and PCR-positivity. Multivariable analysis was performed with a Cox proportional hazards model, with shared-frailty terms for different hospitals included. Results: We included 201 patients (mean age 68 years, 83% male): in 167 patients (83%) SDC was measured, 34 patients (17%) were treated without SDC measurement. First SDC was >5 µg/mL in 106 patients (63%), all with 200 mg doxycycline daily. In patients with SDC measured, dosage was adjusted in 41% (n = 68), concerning an increase in 64 patients. Mean SDC was 4.1 µg/mL before dosage increase, and 5.9 µg/mL afterwards. SDC measurement was associated with a lower risk for disease-related events (HR 0.51, 95% CI 0.26-0.97, P = 0.04), but not with all-cause mortality or PCR-positivity. Conclusions: SDC measurement decreases the risk for disease-related events, potentially through more optimal dosing or improved compliance. We recommend measurement of SDC and striving for SDC >5 µg/mL and <10 µg/mL during treatment of chronic Q fever.

Referral of patients with fever of unknown origin to an expertise center has high diagnostic and therapeutic value.

BACKGROUND: up to 50% of patients with fever of unknown origin (FUO) remain undiagnosed despite extensive evaluation. In expertise centers, at least 25-63% of these patients are referred after evaluation in another hospital. The diagnostic and therapeutic yields of referral to an expertise center are currently unknown. AIM: To determine the diagnostic and therapeutic yield of referral of patients with fever of unknown origin (FUO) that remain undiagnosed in non-expertise hospitals. DESIGN: Data on workup, outcome, treatment and prognosis were extracted from medical records of all 236 patients referred to the Radboud university medical center's department of internal medicine because of FUO between January 2005 and June 2014. RESULTS: A final diagnosis could be made in 110 of 192 tertiary referred FUO patients. The rate of diagnosis did not differ between patients referred for first opinion or after tertiary referral (68.2 vs. 57.3%, P = 0.234). Over half of undiagnosed tertiary referred patients were treated, and fever resolved in half of these patients. Of 96 undiagnosed patients, two died (2.1)% and in both death was considered unrelated to the febrile disease. CONCLUSION: The diagnostic rate in patients with FUO does not differ between patients that are tertiary referred and patients that have not been previously evaluated in another hospital. With a total diagnostic value of 57.3% and an additional therapeutic yield of 10.9% in undiagnosed patients, tertiary referral should therefore be considered in patients that remain undiagnosed in a non-expertise center.

Involvement of matrix metalloproteinases in chronic Q fever.

OBJECTIVES: Chronic Q fever is a persistent infection with the intracellular Gram-negative bacterium Coxiella burnetii, which can lead to complications of infected aneurysms. Matrix metalloproteinases (MMPs) cleave extracellular matrix and are involved in infections as well as aneurysms. We aimed to study the role of MMPs in the pathogenesis of chronic Q fever. METHODS: We investigated gene expression of MMPs through microarray analysis and MMP production with ELISA in C. burnetii-stimulated peripheral blood mononuclear cells (PBMCs) of patients with chronic Q fever and healthy controls. Twenty single nucleotide polymorphisms (SNPs) of MMP and tissue inhibitor of MMP genes were genotyped in 139 patients with chronic Q fever and 220 controls with similar cardiovascular co-morbidity. Additionally, circulating MMPs levels in patients with chronic Q fever were compared with those in cardiovascular controls with and without a history of past Q fever. RESULTS: In healthy controls, the MMP pathway involving four genes (MMP1, MMP7, MMP10, MMP19) was significantly up-regulated in C. burnetii-stimulated but not in Escherichia coli lipopolysaccharide -stimulated PBMCs. Coxiella burnetii induced MMP-1 and MMP-9 production in PBMCs of healthy individuals (both p<0.001), individuals with past Q fever (p<0.05, p<0.01, respectively) and of patients with chronic Q fever (both p<0.001). SNPs in MMP7 (rs11568810) (p<0.05) and MMP9 (rs17576) (p<0.05) were more common in patients with chronic Q fever. Circulating MMP-7 serum levels were higher in patients with chronic Q fever (median 33.5 ng/mL, interquartile range 22.3-45.7 ng/mL) than controls (20.6 ng/mL, 15.9-33.8 ng/mL). CONCLUSION: Coxiella burnetii-induced MMP production may contribute to the development of chronic Q fever.

Intact interferon-γ response against Coxiella burnetii by peripheral blood mononuclear cells in chronic Q fever.

OBJECTIVES: Q fever is caused by Coxiella burnetii, an intracellular bacterium that infects phagocytes. The aim of the present study was to investigate whether the C. burnetii-induced IFN-γ response is defective in chronic Q fever patients. METHODS: IFN-γ was measured in supernatants of C. burnetii-stimulated peripheral blood mononuclear cells (PBMCs) of 17 chronic Q fever patients and 17 healthy individuals. To assess IFN-γ responses, expression profiles of IFN-γ-induced genes in C. burnetii-stimulated PBMCs were studied in six patients and four healthy individuals. Neopterin was measured in PBMC supernatants (of eight patients and four healthy individuals) and in sera (of 21 patients and 11 healthy individuals). In a genetic association study, polymorphisms in genes involved in the Th1-cytokine response were analysed in a cohort of 139 chronic Q fever patients and a cohort of 220 control individuals with previous exposition to C. burnetii. RESULTS: IFN-γ production by C. burnetii-stimulated PBMCs from chronic Q fever patients was significantly higher than in healthy controls. Many IFN-γ response genes were strongly upregulated in PBMCs of patients. Neopterin levels were significantly higher in PBMC supernatants and sera of patients. The IL12B polymorphisms rs3212227 and rs2853694 were associated with chronic Q fever. CONCLUSIONS: IFN-γ production, as well as the response to IFN-γ, is intact in chronic Q fever patients, and even higher than in healthy individuals. Polymorphisms in the IL-12p40 gene are associated with chronic Q fever. Thus, a deficiency in IFN-γ responses does not explain the failure to clear the infection. The genetic data suggest, however, that the IL-12/IFN-γ pathway does play a role.

Rheumatologic diseases as the cause of fever of unknown origin.

In 30% of patients with fever or inflammation of unknown origin (FUO/IUO), the cause is eventually found to be a rheumatologic disease such as autoimmune or granulomatous disease or vasculitis. Most of these patients suffer from an uncommon presentation of a common disease, instead of an uncommon disease. We demonstrate the diagnostic challenge with several cases. The workup of FUO is based on the identification of potential diagnostic clues (PDCs). In the absence of PDCs, a standardized diagnostic protocol should be followed, including early FDG-PET/CT. Other imaging techniques or invasive diagnostic techniques should be reserved for those in whom PDCs are present.

Effectiveness of a multimodal hand hygiene improvement strategy in the emergency department.

BACKGROUND: Hand hygiene (HH) is essential in preventing nosocomial infection. The emergency department (ED) is an open portal of entry for pathogens into the hospital system, hence the important sentinel function of the ED personnel. The main objective of this study was to assess the effect of a multimodal improvement strategy on hand hygiene compliance in the ED. METHODS: Our study was a prospective before-and-after study to determine the effect of a multimodal improvement strategy on the compliance of HH in the ED according to the My 5 Moments of Hand Hygiene defined by the World Health Organization. Interventions such as education, reminders, and regular feedback on HH performance and role models were planned during the 3 intervention weeks. RESULTS: In total, 57 ED nurses and ED physicians were observed in this study, and approximately 1,000 opportunities for handrubs were evaluated during the 3 intervention periods. HH compliance increased significantly from baseline from 18% (74/407) to 41% (77/190) after the first intervention and stabilized to 50% (99/200) and 46% (96/210) after the second and third interventions, respectively. CONCLUSIONS: Implementing a multimodal HH improvement program significantly improved the HH compliance of ED personnel.

The health status of a village population, 7 years after a major Q fever outbreak.

From 2007 to 2010, The Netherlands experienced a major Q fever outbreak with more than 4000 notifications. Previous studies suggested that Q fever patients could suffer long-term post-infection health impairments, especially fatigue. Our objective was to assess the Coxiella burnetii antibody prevalence and health status including fatigue, and assess their interrelationship in Herpen, a high-incidence village, 7 years after the outbreak began. In 2014, we invited all 2161 adult inhabitants for a questionnaire and a C. burnetii indirect fluorescence antibody assay (IFA). The health status was measured with the Nijmegen Clinical Screening Instrument (NCSI), consisting of eight subdomains including fatigue. Of the 70·1% (1517/2161) participants, 33·8% (513/1517) were IFA positive. Of 147 participants who were IFA positive in 2007, 25 (17%) seroreverted and were now IFA negative. Not positive IFA status, but age <50 years, smoking and co-morbidity, were independent risk factors for fatigue. Notified participants reported significantly more often fatigue (31/49, 63%) than non-notified IFA-positive participants (150/451, 33%). Although fatigue is a common sequel after acute Q fever, in this community-based survey we found no difference in fatigue levels between participants with and without C. burnetii antibodies.

Cutaneous hyperpigmentation induced by doxycycline: a case series.

Cutaneous hyperpigmentation is a well-known side effect of tetracyclines, but doxycycline-induced cutaneous hyperpigmentation has only been described in one patient with a therapeutic dosage of doxycycline, and in one patient using suprapharmacological doses. We describe four patients with cutaneous hyperpigmentation in previously unaffected skin, and speculate that this was due to treatment with doxycycline in therapeutic doses. After cessation of therapy, the hyperpigmentation diminished in all four patients, illustrating the need for recognition and timely cessation of therapy.

A combination of interferon-gamma and interleukin-2 production by Coxiella burnetii-stimulated circulating cells discriminates between chronic Q fever and past Q fever.

Infection with Coxiella burnetii may lead to life-threatening chronic Q fever endocarditis or vascular infections, which are often difficult to diagnose. The present study aims to investigate whether measurement of in-vitro interferon-gamma (IFN-γ) production, a key cytokine in the immune response against C. burnetii, differentiates chronic from a past cleared infection, and whether measurement of other cytokines would improve the discriminative power. First, C. burnetii-specific IFN-γ production was measured in whole blood of 28 definite chronic Q fever patients and compared with 135 individuals with past Q fever (seropositive controls) and 908 seronegative controls. IFN-γ production was significantly higher in chronic Q fever patients than in controls, but with overlapping values between patients and seropositives. Secondly, the production of a series of other cytokines was measured in a subset of patients and controls, which showed that interleukin (IL)-2 production was significantly lower in patients than in seropositive controls. Subsequently, measuring IL-2 in all patients and all controls with substantial IFN-γ production showed that an IFN-γ/IL-2 ratio >11 had a sensitivity and specificity of 79% and 96%, respectively, to diagnose chronic Q fever. This indicates that a high IFN-γ/IL-2 ratio is highly suggestive for chronic Q fever. In an additional group of 25 individuals with persistent high anti-Coxiella phase I IgG titres without definite chronic infection, all but six showed an IFN-γ/IL-2 ratio <11. In conclusion, these findings hold promise for the often difficult diagnostic work-up of Q fever and the IFN-γ/IL-2 ratio may be used as an additional diagnostic marker.