Seasonality in carriage of extended-spectrum ß-lactamase-producing Escherichia coli and Klebsiella pneumoniae in the general population: a pooled analysis of nationwide cross-sectional studies.

Infections due to extended-spectrum ß-lactamase-producing Enterobacteriaceae (ESBL-E) are often preceded by asymptomatic carriage. Higher incidences in enteric infectious diseases during summer have been reported. Here, we assessed whether the presence of seasonality in intestinal ESBL-Escherichia coli/Klebsiella pneumoniae (ESBL-E/K) carriage in the general Dutch population exists. From 2014 to 2017, the faecal carriage of ESBL-E/K in healthy individuals was determined in three cross-sectional studies in the Netherlands, including 5985 subjects. Results were pooled to identify seasonal trends in prevalence (by month of sampling). Multivariate logistic regression analysis was used to calculate pooled odds ratios and 95% confidence intervals. Results were adjusted for age, sex, antibiotic use and travel. Overall prevalence of ESBL-E/K carriage was 4.3% (n = 260 ESBL-E/K-positive), with differences between months ranging from 2.6% to 7.4%. Compared to January, the monthly prevalence of ESBL-E carriage was highest in August (OR 1.88, 95% CI 1.02-3.49) and September (OR 2.25, 95% CI 1.30-3.89). The observed monthly differences in ESBL-E/K carriage rates suggest that there is seasonal variation in exposure to ESBL-E/K other than due to travelling and antibiotic use. This should be taken into account in designing future ESBL-E prevalence studies in temperate regions.

Notification data and criteria during a large Q-fever epidemic reassessed.

From 2007 to 2010, the largest reported Q-fever epidemic occurred in the Netherlands with 4026 notified laboratory-confirmed cases. During the course of the epidemic, health-seeking behaviour changed and awareness among health professionals increased. Changes in laboratory workflows were implemented. The aim of this study was to analyse how these changes instigated adjustments of notification criteria and how these adjustments affected the monitoring and interpretation of the epidemic. We used the articles on laboratory procedures related to the epidemic and a description of the changes that were made to the notification criteria. We compared the output of a regional laboratory with notifications to the regional Public Health Service and the national register of infectious diseases. We compared the international notification criteria for acute Q-fever. Screening with ELISA IgM phase II and PCR was added to the diagnostic workflow. In the course of the epidemic, serology often revealed a positive IgG/IgM result although cases were not infected recently. With increasing background seroprevalence, the presence of IgM antibodies can only be suggestive for acute Q-fever and has to be confirmed either by seroconversion of IgG or a positive PCR result. Differences in sero-epidemiology make it unlikely that full harmonisation of notification criteria between countries is feasible.

Prevalence and risk factors for colonization of Clostridium difficile among adults living near livestock farms in the Netherlands.

A cross-sectional study was performed among 2494 adults not living or working on a farm to assess prevalence of Clostridium difficile (CD) colonization and risk factors in a livestock dense area. CD prevalence was 1·2%. Twenty-one persons were colonized with a toxigenic strain and nine with a non-toxigenic strain. CD-positive persons did not live closer to livestock farms than individuals negative for CD. Antibiotic exposure in the preceding 3 months was a risk factor for CD colonization (odds ratio 3·70; 95% confidence interval 1·25-10·95).

Use of a Dose-Response Model to Study Temporal Trends in Spatial Exposure to Coxiella burnetii: Analysis of a Multiyear Outbreak of Q Fever.

The Netherlands underwent a large Q fever outbreak between 2007 and 2009. In this paper, we study spatial and temporal Coxiella burnetii exposure trends during this large outbreak as well as validate outcomes against other published studies and provide evidence to support hypotheses on the causes of the outbreak. To achieve this, we develop a framework using a dose-response model to translate acute Q fever case incidence into exposure estimates. More specifically, we incorporate a geostatistical model that accounts for spatial and temporal correlation of exposure estimates from a human Q fever dose-response model to quantify exposure trends during the outbreak. The 2051 cases, with the corresponding age, gender and residential addresses, reside in the region with the highest attack rates during the outbreak in the Netherlands between 2006 and 2009. We conclude that the multiyear outbreak in the Netherlands is caused by sustained release of infectious bacteria from the same sources, which suggests that earlier implementation of interventions may have prevented many of the cases. The model predicts the risk of infection and acute symptomatic Q fever from multiple exposure sources during a multiple-year outbreak providing a robust, evidence-based methodology to support decision-making and intervention design.

Extended-spectrum ß-lactamase- and pAmpC-producing Enterobacteriaceae among the general population in a livestock-dense area.

OBJECTIVES: In the Netherlands there is an ongoing debate regarding environmental health risks of livestock farming for neighbouring residents. This explorative study aims to determine the prevalence of carriage of extended-spectrum ß-lactamase and/or plasmid-mediated AmpC-producing Enterobacteriaceae (ESBL/pAmpC-E) in the general population living in a livestock-dense area, and to study associations between determinants, including exposure through contact with animals and the environment, and human carriage of ESBL/pAmpC-E. METHODS: A cross-sectional study was performed among 2432 adults (aged 20-72 years) in 12 temporary research centres in the south of the Netherlands, consisting of a questionnaire and analysis of a faecal sample to assess carriage of ESBL/pAmpC-E. Risk factors were analysed using logistic regression. RESULTS: The prevalence for carriage of ESBL/pAmpC-E was 4.5% (109/2432; 95% CI 3.7-5.4) ranging from 1.4% to 10.9% among the research centres. ESBL/pAmpC resistance genes were detected in Escherichia coli and Klebsiella pneumoniae isolates obtained from these 109 persons and the most common ESBL-resistance genes were blaCTX-M-15, blaCTX-M-14/17 and blaCTX-M-1, originating from 76 participants. Travel in the previous 12 months to Africa, Asia or Latin America (OR 2.82; 95% CI 1.71-4.63), having kept cows for a hobby in the previous 5 years (OR 3.77; 95% CI 1.22-11.64), usage of proton-pump inhibitors (OR 1.84; 95% CI 1.05-3.23), and living within 1000 m of a mink farm (OR 2.26; 95% CI 1.28-3.98) were identified as risk factors. Exposure to poultry was not identified as a risk factor. CONCLUSIONS: Overall, living in close proximity to livestock animals and farms does not seem to be a risk factor for carriage of ESBL/pAmpC-E.

Kinetics of antibody response to Coxiella burnetii infection (Q fever): Estimation of the seroresponse onset from antibody levels.

BACKGROUND: From 2007 to 2009, the Netherlands experienced a major Q fever epidemic. Long-term serological follow-up of acute Q fever patients enabled the investigation of longitudinal antibody responses and estimating the onset of the seroresponse in individual patients. METHODS: All available IgG and IgM phase I and II antibody measurements determined by immunofluorescence assay at month 3, 6, 12, and 48 from 2321 acute Q fever patients were retrospectively analyzed. Characteristic features of the antibody response were calculated. To model the seroresponse onset, serological data from patients diagnosed with a positive C. burnetii PCR test (n=364), and therefore with a known time of infection, were used as reference. RESULTS: In 9083 IgG samples and 3260 IgM samples large heterogeneity in shape and magnitude of antibody responses was observed. Phase II reached higher levels than phase I, and IgG antibodies were more persistent than IgM. The estimated seroresponse latency allowed for determining the time since start of the seroresponse from the concentrations of the different antibodies against C. burnetii. CONCLUSIONS: The extraordinary large serological dataset provides new insight into the kinetics of the immunoglobulins against C. burnetii antigens. This knowledge is useful for seroprevalence studies and helps to better understand infection dynamics.

Single nucleotide polymorphisms in immune response genes in acute Q fever cases with differences in self-reported symptoms.

Genes involved in human immune response are well recognized to influence the clinical course of infection. The association of host genetics with susceptibility to and severity of clinical symptoms in acute Q fever was investigated. Single nucleotide polymorphisms (SNPs) in the IFNG (rs2430561/rs1861493), STAT1 (rs1914408), and VDR (rs2228570) genes were determined in 85 patients from the 2007 Dutch acute Q fever outbreak, and a symptom score was calculated. IFNG rs1861493 showed a significant association with the symptom score; IFNG rs2430561 showed a similar trend. These SNPs were then used to reproduce results in a 2009 outbreak population (n = 123). The median symptom score differed significantly in both populations: 2 versus 7. The significant association of IFNG rs1861493 with symptom score in the first population was not reproduced in the second population. We hypothesize that individuals in the second outbreak were exposed to a higher Coxiella burnetii dose compared to the first, which overruled the protection conferred by the A-allele of IFNG rs1861493 in the first population.

Severely impaired health status of non-notified Q fever patients leads to an underestimation of the true burden of disease.

Q fever patients are often reported to experience a long-term impaired health status, including fatigue, which can persist for many years. During the large Q fever epidemic in The Netherlands, many patients with a laboratory-confirmed Coxiella burnetii infection were not notified as acute Q fever because they did not fulfil the clinical criteria of the acute Q fever case definition (fever, pneumonia and/or hepatitis). Our study assessed and compared the long-term health status of notified and non-notified Q fever patients at 4 years after onset of illness, using the Nijmegen Clinical Screening Instrument (NCSI). The study included 448 notified and 193 non-notified Q fever patients. The most severely affected subdomain in both patient groups was 'Fatigue' (50·5% of the notified and 54·6% of the non-notified patients had severe fatigue). Long-term health status did not differ significantly between the notified and non-notified patient groups, and patients scored worse on all subdomains compared to a healthy reference group. Our findings suggest that the magnitude of the 2007-2009 Q fever outbreak in The Netherlands was underestimated when only notified patients according to the European Union case definition are considered.

Correlations between peripheral blood Coxiella burnetii DNA load, interleukin-6 levels, and C-reactive protein levels in patients with acute Q fever.

From 2007 to 2010, the Netherlands experienced the largest reported Q fever outbreak, with >4,000 notified cases. We showed previously that C-reactive protein is the only traditional infection marker reflecting disease activity in acute Q fever. Interleukin-6 is the principal inducer of C-reactive protein. We questioned whether increased C-reactive protein levels in acute Q fever patients coincide with increased interleukin-6 levels and if these levels correlate with the Coxiella burnetii DNA load in serum. In addition, we studied their correlation with disease severity, expressed by hospital admission and the development of fatigue. Interleukin-6 and C-reactive protein levels were analyzed in sera from 102 patients diagnosed with seronegative PCR-positive acute Q fever. Significant but weak negative correlations were observed between bacterial DNA loads expressed as cycle threshold values and interleukin-6 and C-reactive protein levels, while a significant moderate-strong positive correlation was present between interleukin-6 and C-reactive protein levels. Furthermore, significantly higher interleukin-6 and C-reactive protein levels were observed in hospitalized acute Q fever patients in comparison to those in nonhospitalized patients, while bacterial DNA loads were the same in the two groups. No marker was prognostic for the development of fatigue. In conclusion, the correlation between interleukin-6 and C-reactive protein levels in acute Q fever patients points to an immune activation pathway in which interleukin-6 induces the production of C-reactive protein. Significant differences in interleukin-6 and C-reactive protein levels between hospitalized and nonhospitalized patients despite identical bacterial DNA loads suggest an important role for host factors in disease presentation. Higher interleukin-6 and C-reactive protein levels seem predictive of more severe disease.

High Coxiella burnetii DNA load in serum during acute Q fever is associated with progression to a serologic profile indicative of chronic Q fever.

PCR is very effective in diagnosing acute Q fever in the early stages of infection, when bacterial DNA is present in the bloodstream but antibodies have not yet developed. The objective of this study was to further analyze the diagnostic value of semiquantitative real-time PCR (qPCR) in diagnosing acute Q fever in an outbreak situation. At the Jeroen Bosch Hospital, in 2009, qPCR testing for Coxiella burnetii DNA was performed for 2,715 patients suspected of having acute Q fever (positive, n = 385; negative, n = 2,330). The sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of the qPCR assay were calculated for patients with negative qPCR results with a follow-up sample obtained within 14 days (n = 305) and qPCR-positive patients with at least one follow-up sample (n = 369). The correctness of the qPCR result was based on immunofluorescence assay results for samples submitted for qPCR and follow-up testing. The sensitivity of the Q fever qPCR assay was 92.2%, specificity 98.9%, PPV 99.2%, and NPV 89.8%. Patients who later developed serologic profiles indicative of chronic Q fever infection had significantly higher C. burnetii DNA loads during the acute phase than did patients who did not (P < 0.001). qPCR testing is a valuable tool for the diagnosis of acute Q fever and should be used in outbreak situations when the onset of symptoms is <15 days earlier. Special attention is needed in the follow-up monitoring of patients with high C. burnetii DNA loads during the acute phase, as this might be an indicator for the development of a serologic profile indicative of chronic infection.

Screening for Coxiella burnetii seroprevalence in chronic Q fever high-risk groups reveals the magnitude of the Dutch Q fever outbreak.

The Netherlands experienced an unprecedented outbreak of Q fever between 2007 and 2010. The Jeroen Bosch Hospital (JBH) in 's-Hertogenbosch is located in the centre of the epidemic area. Based on Q fever screening programmes, seroprevalence of IgG phase II antibodies to Coxiella burnetii in the JBH catchment area was 10·7% [785 tested, 84 seropositive, 95% confidence interval (CI) 8·5-12·9]. Seroprevalence appeared not to be influenced by age, gender or area of residence. Extrapolating these data, an estimated 40 600 persons (95% CI 32 200-48 900) in the JBH catchment area have been infected by C. burnetii and are, therefore, potentially at risk for chronic Q fever. This figure by far exceeds the nationwide number of notified symptomatic acute Q fever patients and illustrates the magnitude of the Dutch Q fever outbreak. Clinicians in epidemic Q fever areas should be alert for chronic Q fever, even if no acute Q fever is reported.

Early diagnosis and treatment of patients with symptomatic acute Q fever do not prohibit IgG antibody responses to Coxiella burnetii.

Little is known about the effect of timing of antibiotic treatment on development of IgG antibodies following acute Q fever. We studied IgG antibody responses in symptomatic patients diagnosed either before or during development of the serologic response to Coxiella burnetii. Between 15 and 31 May 2009, 186 patients presented with acute Q fever, of which 181 were included in this retrospective study: 91 early-diagnosed (ED) acute Q fever patients, defined as negative IgM phase II enzyme-linked immunosorbent assay (ELISA) and positive PCR, and 90 late-diagnosed (LD) acute Q fever patients, defined as positive/dubious IgM phase II ELISA and positive immunofluorescence assay (IFA). Follow-up serology at 3, 6, and 12 months was performed using IFA (IgG phase I and II). High IgG antibody titers were defined as IgG phase II titers of ≥1:1,024 together with IgG phase I titers of ≥1:256. At 12 months, 28.6% of ED patients and 19.5% of LD patients had high IgG antibody titers (P = 0.17). No statistically significant differences were found in frequencies of IgG phase I and IgG phase II antibody titers at all follow-up appointments for adequately and inadequately treated patients overall, as well as for ED and LD patients analyzed separately. Additionally, no significant difference was found in frequencies of high antibody titers and between early (treatment started within 7 days after seeking medical attention) and late timing of treatment. This study indicates that early diagnosis and antibiotic treatment of acute Q fever do not prohibit development of the IgG antibody response.

Detection of phase I IgG antibodies to Coxiella burnetii with EIA as a screening test for blood donations.

The presence of a high phase I IgG antibody titre may indicate chronic infection and a risk for the transmission of Coxiella burnetii through blood transfusion. The outbreak of Q fever in the Netherlands allowed for the comparison of an enzyme immunoassay (EIA) with the reference immunofluorescence assay (IFA) in a large group of individuals one year after acute Q fever. EIA is 100 % sensitive in detecting high (≥1:1,024) phase I IgG antibody titres. The cost of screening with EIA and confirming all EIA-positive results with IFA is much lower than screening all donations with IFA. This should be taken into account in cost-effectiveness analyses of screening programmes.

Evaluation of commonly used serological tests for detection of Coxiella burnetii antibodies in well-defined acute and follow-up sera.

In this study, we compared Coxiella burnetii IgG phase I, IgG phase II, and IgM phase II detection among a commercially available enzyme-linked immunosorbent assay (ELISA) (Virion/Serion), an indirect fluorescent antibody test (IFAT) (Focus Diagnostics), and a complement fixation test (CFT) (Virion/Serion). For this, we used a unique collection of acute- and convalescent-phase sera from 126 patients with acute Q fever diagnosed by positive Coxiella burnetii PCR of blood. We were able to establish a reliable date of onset of disease, since DNA is detectable within 2 weeks after the start of symptoms. In acute samples, at t = 0, IFAT demonstrated IgM phase II antibodies in significantly more sera than did ELISA (31.8% versus 19.7%), although the portion of solitary IgM phase II was equal for IFAT and for ELISA (18.2% and 16.7%, respectively). Twelve months after the diagnosis of acute Q fever, 83.5% and 62.2% of the sera were still positive for IgM phase II with IFAT and ELISA, respectively. At 12 months IFAT IgG phase II showed the slowest decline. Therefore, definitive serological evidence of acute Q fever cannot be based on a single serum sample in areas of epidemicity and should involve measurement of both IgM and IgG antibodies in paired serum. Based on IgG phase II antibody detection in paired samples (at 0 and 3 months) from 62 patients, IFAT confirmed more cases than ELISA and CFT, but the differences were not statically significant (100% for IFAT, 95.2% for ELISA, and 96.8% for CFT). This study demonstrated that the three serological tests are equally effective in diagnosing acute Q fever within 3 months of start of symptoms. In follow-up sera, more IgG antibodies were detected by IFAT than by ELISA or CFT, making IFAT more suitable for prevaccination screening programs.

The burden of 2009 pandemic influenza A(H1N1) in the Netherlands.

BACKGROUND: The disease burden of the 2009 influenza pandemic has been debated but reliable estimates are lacking. To guide future policy and control, these estimates are necessary. This study uses burden of disease measurements to assess the contribution of the pandemic influenza A(H1N1) virus to the overall burden of disease in the Netherlands. METHODS: The burden of disease caused by 2009 pandemic influenza was estimated by calculating Disability Adjusted Life Years (DALY), a composite measure that combines incidence, sequelae and mortality associated with a disease, taking duration and severity into account. Available influenza surveillance data sources (primary care sentinel surveillance, notification data on hospitalizations and deaths and death registries) were used. Besides a baseline scenario, five alternative scenarios were used to assess effects of changing values of input parameters. RESULTS: The baseline scenario showed a loss of 5800 DALY for the Netherlands (35 DALY per 100 000 population). This corresponds to 0.13% of the estimated annual disease burden in the Netherlands and is comparable to the estimated disease burden of seasonal influenza, despite a different age distribution in incidence and mortality of the pandemic compared to seasonal influenza. CONCLUSIONS: This disease burden estimate confirmed that, although there was a higher mortality observed among young people, the 2009 pandemic was overall a mild influenza epidemic. The disease burden of this pandemic was comparable to the burden of seasonal influenza in the Netherlands.

Mumps epidemic in orthodox religious low-vaccination communities in the Netherlands and Canada, 2007 to 2009.

We assessed the epidemiological characteristics of a mumps virus epidemic (genotype D) that occurred in the Netherlands between August 2007 and May 2009 and its association with a subsequent mumps outbreak in Canada. In the Netherlands, five data sources were used: notifications (only mandatory since the end of 2008) (56 cases), laboratory confirmation data (177 cases), a sentinel general practitioner (GP) database (275 cases), hospitalisation data (29 cases) and weekly virological reports (96 cases). The median age of cases in the notification, laboratory and GP databases ranged from 13 to 15 years. The proportion of cases that were unvaccinated ranged from 65% to 85% in the notification, laboratory and GP databases. Having orthodox Protestant beliefs was the main reason for not being vaccinated. In Canada, a mumps virus strain indistinguishable from the Dutch epidemic strain was detected between February and October 2008 in an orthodox Protestant community with historical and family links to the affected community in the Netherlands, suggesting that spread to Canada had occurred. Prevention and control of vaccine-preventable diseases among population subgroups with low vaccination coverage remains a priority.

Risk factors for severe outcomes following 2009 influenza A (H1N1) infection: a global pooled analysis.

BACKGROUND: Since the start of the 2009 influenza A pandemic (H1N1pdm), the World Health Organization and its member states have gathered information to characterize the clinical severity of H1N1pdm infection and to assist policy makers to determine risk groups for targeted control measures. METHODS AND FINDINGS: Data were collected on approximately 70,000 laboratory-confirmed hospitalized H1N1pdm patients, 9,700 patients admitted to intensive care units (ICUs), and 2,500 deaths reported between 1 April 2009 and 1 January 2010 from 19 countries or administrative regions--Argentina, Australia, Canada, Chile, China, France, Germany, Hong Kong SAR, Japan, Madagascar, Mexico, The Netherlands, New Zealand, Singapore, South Africa, Spain, Thailand, the United States, and the United Kingdom--to characterize and compare the distribution of risk factors among H1N1pdm patients at three levels of severity: hospitalizations, ICU admissions, and deaths. The median age of patients increased with severity of disease. The highest per capita risk of hospitalization was among patients <5 y and 5-14 y (relative risk [RR] = 3.3 and 3.2, respectively, compared to the general population), whereas the highest risk of death per capita was in the age groups 50-64 y and ≥65 y (RR = 1.5 and 1.6, respectively, compared to the general population). Similarly, the ratio of H1N1pdm deaths to hospitalizations increased with age and was the highest in the ≥65-y-old age group, indicating that while infection rates have been observed to be very low in the oldest age group, risk of death in those over the age of 64 y who became infected was higher than in younger groups. The proportion of H1N1pdm patients with one or more reported chronic conditions increased with severity (median = 31.1%, 52.3%, and 61.8% of hospitalized, ICU-admitted, and fatal H1N1pdm cases, respectively). With the exception of the risk factors asthma, pregnancy, and obesity, the proportion of patients with each risk factor increased with severity level. For all levels of severity, pregnant women in their third trimester consistently accounted for the majority of the total of pregnant women. Our findings suggest that morbid obesity might be a risk factor for ICU admission and fatal outcome (RR = 36.3). CONCLUSIONS: Our results demonstrate that risk factors for severe H1N1pdm infection are similar to those for seasonal influenza, with some notable differences, such as younger age groups and obesity, and reinforce the need to identify and protect groups at highest risk of severe outcomes. Please see later in the article for the Editors' Summary.

Surveillance of hospitalisations for 2009 pandemic influenza A(H1N1) in the Netherlands, 5 June - 31 December 2009.

We analysed and reported on a weekly basis clinical and epidemiological characteristics of patients hospitalised in the Netherlands for the 2009 pandemic influenza A(H1N1) using information from the national mandatory notification system. The notification criteria changed on 15 August 2009 from all possible, probable and confirmed cases to only laboratory-confirmed pandemic influenza hospitalisations and deaths. In the period of comprehensive case-based surveillance (until 15 August), 2% (35/1,622) of the patients with pandemic influenza were hospitalised. From 5 June to 31 December 2009, a total of 2,181 patients were hospitalised. Of these, 10% (219/2,181) were admitted to an intensive care unit (ICU) and 53 died. Among non-ICU hospitalised patients, 56% (961/1,722) had an underlying medical condition compared with 70% (147/211) of the patients in ICU and 46 of the 51 fatal cases for whom this information was reported. Most common complications were dehydration among non-ICU hospitalised patients and acute respiratory distress syndrome among patients in ICU and patients who died. Children under the age of five years had the highest age-specific hospitalisation rate (62.7/100,000), but relatively few were admitted to an ICU (1.7/100,000). Characteristics and admission rates of hospitalised patients were comparable with reports from other countries and previous influenza seasons. The national notification system was well suited to provide weekly updates of relevant monitoring information on the severity of the pandemic for professionals, decision makers, the media and the public, and could be rapidly adapted to changing information requirements.