While Lyme disease (LD) is the most common tick-borne disease reported to public health surveillance in North America and is increasingly recognized as a public health threat in Canada, it's incidence may be underreported. Our study aims to estimate medically-attended LD incidence in Manitoba, Canada, using administrative health data. We identified medically-attended LD cases in Manitoba from 2010 - 2021 in a claims database (Manitoba Population Research Data Repository), which contains the health records of >95% of the residents of Manitoba, using diagnostic codes, antibiotic dispensations, and laboratory results. The incidence of claims-based LD cases ranged from 8.4 to 28.5 per 100,000 population per year, 5.1 to 11.0 times higher than the incidence of surveillance-reported LD cases. The incidence of claims-based LD cases was particularly higher than the incidence of surveillance-reported LD cases in females and health regions with a low surveillance-reported incidence. Our study suggests that medically attended LD is more common than reported in surveillance. Further study is required to identify barriers to reporting. Interventions are needed to reduce the substantial burden of LD in Manitoba.

Lyme borreliosis (LB) is endemic in many European countries. The prospective, epidemiological Burden of Lyme Disease (BOLD) study used unified case definitions to characterise LB burden in Europe. A retrospective case–control study was nested within the BOLD study to better understand LB risk factors. LB patients were evaluated at 14 healthcare practices in high-LB-incidence areas in six European countries: the Czech Republic, Germany, Poland, Slovakia, Slovenia, and Sweden between April 2021 and December 2022. Enrolled cases and age-group-matched controls were interviewed about potential risk factors, and multivariate regression analysis was used to analyse the responses. Patients with LB were more likely than matched controls to live in neighbourhoods with >50% woods, to have a garden that is composed of less than half dense trees, and to have a garden visited by wild animals. Characteristics associated with lower LB risk included being male and not having a bird feeder. The results are suggestive of risk associated with edge-of-the-forest areas, aligning with the previous literature on the increased risk of LB with forest fragmentation. Our findings support the importance of landscape structure and human–environment interactions in shaping LB risk.

Lyme borreliosis (LB), the most common European tick-borne disease, can manifest as an erythema migrans (EM) rash or as disseminated LB. The prospective Burden of Lyme Disease (BOLD) study evaluated the frequency of LB clinical manifestations, including signs, symptoms, and treatment patterns in 14 healthcare practices in endemic regions of six European countries: the Czech Republic, Germany, Poland, Slovakia, Slovenia, and Sweden. Between April 2021 and December 2022, patients with suspected LB were evaluated using predefined case definitions that were applied by investigators to identify medically attended LB cases. Enrolled cases were interviewed about their symptoms. Among the 797 LB cases, 615 (77.2%) had EM and 182 (22.8%) had disseminated disease; 154 of the disseminated cases had Lyme arthritis (LA), five had Lyme neuroborreliosis, and three had Lyme carditis. Geographically, the proportion of disseminated disease varied by country, from 1.1% in Slovenia to 78.0% in Slovakia. Overall, 76.3% of all LB cases in Slovakia were LA. Antibiotic use varied by country, although every country prescribed doxycycline. The frequency of LB manifestations varied substantially between countries. EM was the most common manifestation in all countries except Slovakia, where LA was most common. This study underscores the need for improved prevention strategies.

BACKGROUND/OBJECTIVES:Although Clostridioides difficile infection (CDI) is a key cause of global morbidity and mortality, the burden of CDI in mainland China is not well-defined. The objective of this systematic literature review was to summarize the available epidemiologic evidence on the CDI disease burden (cases, hospitalizations, and deaths) in mainland China. METHODS:Six databases (three global [PubMed, Embase, Cochrane] and three Chinese [Chinese National Knowledge Infrastructure, Chinese Science Citation, Wanfang]) were searched on 5 August 2025 using CDI-related and epidemiological search terms. No date or language limits were applied. Real-world epidemiologic studies of adults and/or children with laboratory-confirmed CDI in mainland China reporting population-based CDI incidence, hospital-based CDI incidence, and/or CDI admission rates were included. All studies not meeting these criteria were excluded. Risk-of-bias (RoB) assessment was performed using the Newcastle-Ottawa Scale. Results were summarized descriptively. RESULTS:In total, 11 articles formed the evidence base for this review; each was a single-center, hospital-based study conducted in one of six cities in mainland China and published between 2014 and 2023. RoB assessment indicated that the evidence base was appropriate for this study. No study reported population-based CDI incidence. In total, 10 studies reported hospital-based CDI incidence (0 to 82.0/10,000 patient-days), and four reported CDI admission rates (0 to 23.1/1000 admissions). Eight studies reported mortality rates, which varied across studies. CONCLUSIONS:Several single-center, hospital-based studies demonstrate that CDI is present in hospitals in mainland China, but there are no published population-based CDI incidence estimates. These results should be interpreted considering this study's limitations, including potential publication and selection bias, heterogeneity, and limited generalizability. Overall, the burden of CDI is poorly understood in mainland China. Thus, prospective epidemiological studies, including those with sensitive detection methods, are needed to examine CDI burden across multiple cities in mainland China. These efforts would help illuminate the CDI burden and guide prevention efforts. (PROSPERO ID 1140152; registered 17 March 2026; funding by Pfizer Inc.).

Introduction: The aim of this study was to investigate the seroprevalence of IgG antibodies to Borrelia burgdorferi sensu lato (Bbsl) in the Swedish population, an indication of ongoing or previous Bbsl infection, by assessing seroprevalence among healthy blood donors covering all administrative regions.Methods: Sera from 2058 healthy adult blood donors were collected during 2024 in Sweden’s 21 administrative regions. Anti-Bbsl IgG antibodies were detected in sera using Liaison Borrelia IgG VlsE kit as a screening test and Anti-Borrelia EUROLINE-RN-AT IgG as a confirmatory test.Results: The analyses revealed an overall seroprevalence of 16% with significant differences between age groups, sexes and geographical regions. The seroprevalence in females was 11% compared to 21% in males (p<0.0001). Seroprevalence increased with age, from 8% in the youngest age group (18-29 years) to 29% in the oldest age group (60 years and above) (p<0.0001). The seroprevalence was higher in the southern and central parts of the country (17-19%), compared to the northern part (5%) (p<0.001). Among the 21 Swedish administrative regions, the seroprevalence ranged from 0% in Region Norrbotten to 27% in Region Gotland. Conclusions: Except for the Northern part of Sweden, the seroprevalence of antibodies to Bbsl indicates that a substantial proportion of the population has been infected with Bbsl. The seroprevalence varies with sex and across different age groups, which should be taken into consideration in the interpretation of serological test results for the diagnosis of LB. Furthermore, the outcomes of the study indicate that the LB disease burden may be substantial in Sweden.

Up to 10% of patients with Lyme borreliosis (LB) will experience symptoms that fulfill the Infectious Disease Society of America (IDSA) criteria of post-treatment Lyme disease syndrome (PTLDS). This study assesses PTLDS in the Burden of Lyme Disease (BOLD) study through clinical assessment (“PTLDS Assessed by Clinicians”) and by post hoc evaluation of patient-reported outcomes, including the 36-Item Short Form Health Survey, Fatigue Severity Scale, and Cognitive Failures Questionnaire (“PTLDS Assessed by Questionnaire”). Among 242 LB cases who completed antibiotic treatment and had objective manifestations stabilized or resolved, 99 (40.9%) reported ≥1 symptom of fatigue, musculoskeletal pain, or cognitive impairment 10 months after diagnosis. Fifteen (6.2%) cases met the PTLDS criteria assessed by either clinicians or predefined questionnaire severity thresholds; four (1.7%) met both. PTLDS cases assessed by questionnaires and LB cases with persistent symptoms both reported greater symptom severity and poorer physical functioning than PTLDS cases assessed by clinicians. These exploratory findings suggest that clinician- and questionnaire-based assessments may identify partially different subsets of patients with PTLDS and either method could underestimate the proportion of patients with PTLDS.

Objectives:Antibodies against tick-borne encephalitis (TBE) virus (TBEV) nonstructural protein 1 (NS1) immunoglobulin G are elevated in TBEV-infected individuals, but not in TBE vaccinated individuals, enabling estimation of TBEV infection prevalence in countries where TBE vaccines are used. Methods:We used data from NS1 seroprevalence studies to estimate the incidence of medically attended TBEV infections and then compared this incidence with the incidence of surveillance-reported TBE cases to estimate the under-ascertainment multiplier for medically attended TBEV infections identified by surveillance. Results:The prevalence of NS1 antibodies ranged from 0.1% to 7.0% in the identified nine seroprevalence studies. Medically attended TBEV incidence in areas where seroprevalence specimens were collected ranged from 0.5/100,000 population per year in Denmark to 21.5/100,000 population per year in Latvia. The under-ascertainment multiplier was 0.9 in Finland, 2.2 in Latvia, 2.5 in Switzerland, 3.4 in Sweden, 3.6 in Austria(Northern), 3.8 in Germany (Bavaria), 5.0 in Austria (Western), 5.0 in Denmark, and 6.0 in Germany-Baden/Wuerttemberg. Conclusion:Despite assumptions necessitated by data gaps, the results of this analysis indicate that more individuals are infected with TBEV and seek medical care than are ascertained by TBE surveillance. Given the increasing public health threat posed by TBE in Europe, further efforts are needed to improve TBE awareness and increase TBE vaccination among persons at increased risk of TBEV infection.

Slovenia has a high tick-borne encephalitis (TBE) incidence and TBE vaccination is recommended for all residents ≥1 year-of-age. Despite widespread TBE vaccine use in Slovenia, TBE vaccine effectiveness (VE) has not been reported for Slovenia. We defined individuals who received ≥3 TBE vaccine doses in accordance with the recommended vaccination schedule as fully vaccinated. Using the screening method, TBE VE was determined by comparing the proportions of TBE cases and survey respondents who were fully vaccinated. TBE incidence and VE were used to estimate the number of TBE cases prevented by TBE vaccination. Of 637 surveillance-reported TBE cases in 2019-2024, 332 (52.1%) had a known vaccination history. Of these 332 TBE cases, 322 (97.0%) were unvaccinated and 10 (3.0%) received ≥1 doses of a TBE vaccine. Among 25,242 persons surveyed with known TBE vaccination history, 57.9% were unvaccinated. VE of ≥3 TBE doses for the prevention of TBE was 93.4% (84.0-97.3%). TBE vaccination prevented 426 TBE cases in 2019-2024. If the entire population was vaccinated against TBE, vaccination would have prevented 994 TBE cases in 2019-2024. TBE vaccination in Slovenia was highly effective, preventing hundreds of TBE cases a year. Most of the Slovenian population, however, is not vaccinated against TBE. To prevent additional TBE cases in Slovenia, further efforts are needed to enhance TBE vaccine uptake.

INTRODUCTION:Lyme disease (LD), the most common vector-borne disease in the United States, is caused by the transmission of bacteria via the bite of infected Ixodes ticks including Ixodes scapularis. Deciduous forests are a highly suitable habitat for I. scapularis survival and development. This case-control study investigated how LD risk was impacted by residential proximity to deciduous forest land cover. MATERIALS AND METHODS:Participants were selected from the Optum Research Database and mailed a one-time survey regarding LD history, outdoor activities, residential characteristics, and demographics. Cases were identified through the combination of LD diagnosis codes and antibiotic treatment in claims data during January 2020-January 2022; controls were matched based on residential county and census block group housing density. The National Land Cover Database was used to identify the presence and proportion of deciduous land cover within a 50 m and 500 m radius of participants' residential addresses. RESULTS:LD was associated with deciduous land cover when present at both a 50 and 500 m radius (odds ratio [OR] = 1.80, 95% confidence interval [CI]: 1.33-2.44) and when present at the 500 m radius only (OR = 1.40, 95% CI: 1.04-1.88). Odds of LD also significantly increased with increasing deciduous cover. Independent of residential proximity to deciduous land cover, spending time in yards or hiking/walking/running in wooded/grassy areas was associated with LD. Stratified stepwise models showed that for individuals with deciduous land cover within both 50 and 500 m, risk was uniformly elevated regardless of activity, whereas outdoor activities were significant predictors in individuals with deciduous land cover within the 500 m radius only or within neither radius. CONCLUSION:This study identified the presence of deciduous land cover as a key indicator associated with increased LD risk, though outdoor activities conferred increased risk independent of residential land cover. Furthermore, individual behaviors were found to modulate LD risk differently across residential contexts.

In Japan, Lyme disease and tick-borne encephalitis (TBE) are primarily in the northernmost prefecture Hokkaido, where their primary vectors Ixodes ovatus and Ixodes persulcatus are most abundant. Recently, tick surveillance activities have collected both species across Japan, indicating potential expansion of their tick-borne pathogens (TBPs). We built a machine-learning (ML) model using available tick surveillance and environmental data to predict suitable habitat areas for I. ovatus and I. persulcatus and identify potential higher-risk areas of Lyme disease and TBE across Japan. Data on the occurrence and abundance of 11 vector tick species between 1990 and 2023 were extracted from studies identified via systematic literature search in two online databases or provided by local experts for ML development. After multiple iterations and permutations, separate Random Forest ML algorithms for I. ovatus and I. persulcatus were trained via 26 abiotic variables of climate and topography based on the occurrence and abundance respective to each species. Data on 93,289 ticks from 57 sources were extracted, and the ML algorithms' area under the curves were high (> 0.89). Climate-related variables were the strongest predictors (> 90% cumulative model importance) for both I. ovatus and I. persulcatus. High suitability for both species was identified in Hokkaido and cooler, wetter regions in central Honshu, while I. ovatus had a broader ecological niche than I. persulcatus, with moderate suitability in mountainous regions of central Kyushu and surrounding the Tokyo Bay area. Our ML models suggest high suitability areas for Ixodes vectors may be widespread in Japan, indicating expanding potential risks of TBPs.

OBJECTIVES:Little is known about the impact of Clostridioides difficile infection (CDI) on health-related quality of life (HRQoL) among adults in the community. We examined the impact of CDI on HRQoL among adults with CDI in the outpatient setting and compared it to HRQoL among patients without CDI. METHODS:We conducted a prospective study among adult Kaiser Permanente members ≥50 years with CDI in the outpatient setting (cases) and members ≥45 years who had an outpatient encounter without diarrhea or C. difficile (controls). Cases and controls were not hospitalized within 7 days. Cases and controls completed the EQ-5D-5L at baseline and after 60 days. RESULTS:Our analyses included 213 adults with CDI and 426 adults without CDI. Adults with and without CDI reported similar perceived health status [median visual analogue scale (VAS) of 80.0 and 81.0, (p = 0.08)] and utility index scores [median of 0.9 for both; (p = 0.16)] before illness. On their worst day, adults with CDI reported lower perceived health status and utility index scores, compared to pre-infection (p < 0.0001). Decrements in median VAS and utility indices among adults with CDI from pre-infection to worst day were significantly greater than decrements among adults without CDI (p < 0.0001 for both). At 60 days, adults with and without CDI had VAS and utility index scores similar to pre-illness levels. CONCLUSIONS:Adults with CDI experienced significant reductions in HRQoL on the worst day of illness that were greater than that experienced by those without CDI. HRQoL among adults with CDI at 60 days was similar to pre-infection levels.

Background:Infection with the tick-borne encephalitis virus (TBEV) can affect the nervous system and lead to significant morbidity. To summarize current knowledge of long-term outcomes following TBEV infection, we systematically reviewed the prevalence of TBEV infection sequelae after hospital discharge across different age groups and follow-up time points. Methods:Studies of adults, children, and "all-age" populations with laboratory-confirmed TBEV infection were identified via electronic database searches. Study categorization was based on follow-up time after hospital discharge: ≤6, 7 to ≤12, or >12 months. Sequelae signs/symptoms were divided into 3 categories: neurological, neuropsychiatric, and other. Data were normalized using weighted means. Heterogeneity was estimated using a meta-analytic random-effects model. Results:Fifteen studies were eligible for analysis (13 included only hospitalized patients). Seventy-nine unique sequelae symptoms were identified. Adults had a higher frequency of persistent symptoms than children (20.6%-100% vs 1.7%-69%). There were high levels of data heterogeneity (I 2 > 90%) among all studies. Although the proportion of patients with each sequela fluctuated across time, headache was reported by ≥20% of patients at all time points. Some sequelae also varied by age group; for example, irritability was more frequent in children, while insomnia/sleep disorders were more frequent in adults. Predominant neurological symptoms included balance disorders and headache. Predominant neuropsychiatric symptoms included concentration and memory disorders. Conclusions:Patients experience a variety of neurological, neuropsychiatric, or other sequelae symptoms following TBEV infection that vary over time and across age groups. This study highlights the need for standardized symptom categorization and follow-up time for TBE sequelae studies.

BACKGROUND:To characterize Clostridioides difficile isolates identified during a prospective multi-hospital population-based study of C. difficile infection (CDI). METHODS:Between December 2018 and March 2020, inpatients ≥50 years of age with new-onset diarrhea in nine Tokyo hospitals were investigated for CDI. Stool specimens were screened by C. DIFF QUIK CHEK COMPLETE® and glutamate dehydrogenase (GDH) positive stools tested by Xpert® C. difficile/Epi PCR assay. PCR positive stools were tested by cytotoxicity neutralization assay to determine presence of functional toxin. GDH positive stools were also anaerobically cultured and whole genome sequences of C. difficile isolates were acquired. RESULTS:Toxigenic C. difficile were isolated from 64 patients with CDI; 22 were RT018/356, 9 were RT369, 4 each were RT106 and RT002, 15 were other RTs, and 10 had an unknown RT. Four isolates were positive for binary toxin: one isolate each of RT027, RT078/126, RT080, and one unknown. In terms of the pathogenicity locus profile, 55 were tcdA+/tcdB+ and 9 were tcdA-/tcdB+. In terms of ST, 23 were ST17, nine were ST81, 31 were other STs, and one had a novel ST. CONCLUSIONS:Consistent with prior studies, C. difficile isolates from patients with CDI represented diverse ribotypes with approximately one third of isolates RT018/356. Of note, one isolate each of RT027 and RT078/126 were identified, indicating these hypervirulent strains are present in hospitals in Japan. Public health interventions are needed to reduce the CDI burden in Japan.

Tick-borne encephalitis (TBE) is an increasing health threat in Sweden and elsewhere in Europe. TBE vaccination is commonly recommended in Sweden, but limited data are available on uptake, effectiveness, and impact of TBE vaccination. General population surveys conducted in 2019-2022 were used to estimated TBE vaccine uptake. TBE vaccine effectiveness (VE) was estimated using the screening method utilizing the surveys and public health TBE surveillance data, which predominately includes hospitalized TBE cases, from 2018 to 2022. Impact of TBE vaccination was calculated based on disease incidence and observed VE. In 2018-2022, 2,015 TBE cases were reported in Sweden; 82.8% (1,564/1,890) of cases with known TBE vaccination history were unvaccinated. Among persons surveyed from the general population with known vaccination history, 52.0% (11,562/22,247) were unvaccinated. Three dose VE against TBE was 89.0% (95% confidence interval 84.3-92.4). When stratified by age group, VE was 86.0% (55.7-95.6) in 1-15 years-of-age and 93.8% (87.5-96.9) in 16-49 years-of-age. In a conservative estimate, despite suboptimal compliance with TBE vaccination recommendations, vaccination averted an estimated thousand TBE cases, most resulting in hospitalization, in Sweden from 2018 to 2022. To prevent additional TBE cases in Sweden, enhanced efforts to increase TBE vaccine uptake and compliance to the TBE vaccination schedule are needed.

Categorization systems for tick-borne encephalitis virus (TBEV) infection lack consistency in classifying disease severity. To evaluate the need for a standard, consensus-based categorisation system for TBEV infection across subtypes, we gathered an expert panel of clinicians and scientists with diverse expertise in TBEV infection. Consensus was sought using the Delphi technique, which consisted of 2 web-based survey questionnaires and a final, virtual, consensus-building exercise. Ten panellists representing 8 European countries participated in the Delphi exercise, with specialities in neurology, infectious disease, paediatrics, immunology, virology, and epidemiology. Panellists reached unanimous consensus on the need for a standardised, international categorisation system to capture both clinical presentation and severity of TBEV infection. Ideally, such a system should be feasible for use at bedside, be clear and easy to understand, and capture both the acute and follow-up phases of TBEV infection. Areas requiring further discussion were (1) the timepoints at which assessments should be made and (2) whether there should be a separate system for children. This Delphi panel study found that a critical gap persists in the absence of a feasible and practical classification system for TBEV infection. Specifically, the findings of our Delphi exercise highlight the need for the development of a user-friendly classification system that captures the acute and follow-up (i.e., outcome) phases of TBEV infection and optimally reflects both clinical presentation and severity. Development of a clinical categorisation system will enhance patient care and foster comparability among studies, thereby supporting treatment development, refining vaccine strategies, and fortifying public health surveillance.

BACKGROUND:Tick-borne encephalitis (TBE) is a vaccine-preventable disease. While many European countries conduct TBE surveillance, resulting incidence estimates do not distinguish between vaccinated and unvaccinated populations. To understand TBE risk to unvaccinated individuals, we assessed incidence among unvaccinated populations in Europe. METHODS:TBE incidence was calculated as cases per 100,000 population per year (PPY) using publicly available surveillance data for 34 countries (2020-2023). Unvaccinated incidence was calculated for 21 countries using TBE vaccine uptake data from population surveys, and assuming 95.1% of TBE cases were unvaccinated. The number of cases averted by vaccination in 2023 was also estimated. RESULTS:The surveillance-reported TBE incidence (2020-2023) was ≥5 per 100,000 PPY for Lithuania, Latvia, Estonia, Czechia, and Slovenia. When the unvaccinated incidence is calculated, Sweden and Austria also had an incidence ≥5 per 100,000 PPY. In 2023, 2498 TBE cases were estimated to have been averted in 21 countries by vaccination. CONCLUSION:The incidence of TBE remains a significant public health concern, with >35 million people living in highly endemic areas of Europe. TBE incidence in the unvaccinated population is substantially higher than the incidence of surveillance-reported TBE cases. Enhanced efforts are needed to increase the uptake of preventive measures, including vaccination.

Abstract Background Lyme borreliosis (LB) is the most common tick-borne disease in Europe. Many European countries conduct LB surveillance. However, many symptomatic Bbsl infections are not detected by surveillance. The aim of this study was to estimate the incidence of symptomatic Borrelia burgdorferi sensu lato (Bbsl) infection, including cases not detected or reported by LB surveillance. Methods Seroprevalence studies of anti-Bbsl antibodies published in 1998−2023, along with estimates of the symptomatic proportion and persistence of antibodies among Bbsl-infected individuals from studies published in 1990−2023, were used to estimate the incidence of symptomatic Bbsl infection. This incidence was then compared to the incidence of surveillance-reported LB to derive country-specific multipliers and estimate the incidence of symptomatic Bbsl infection from 2018−2022. Results Seroprevalence and LB surveillance data were available in nine countries; the prevalence of individuals with anti-Bbsl IgG antibodies ranged from 2.3% in Romania to 9.4% in Germany (Table 1). The pooled estimate of the symptomatic proportion among Bbsl-infected persons from five studies was 37% (95% confidence interval 28%­­−46%). There was a wide range (0.4−33.3 years) of persistence of antibodies in seven studies; therefore, a 10-year duration (scenario #1) and 20-year duration (scenario #2) were used for the duration of antibody detection. Under-detection multipliers varied across surveillance systems (Table 2). Under scenario #1, under-detection multipliers were 2.3−10.5 in countries reporting all LB cases and 54.6−772.2 in countries reporting only Lyme neuroborreliosis (LNB) cases. Under scenario #2, under-detection multipliers were 50% lower than the multipliers under scenario #1. Under both scenarios, the incidence of symptomatic Bbsl infection adjusted for under-detection was highest in Finland, Germany, Norway, Poland, and Switzerland, intermediate in the Czech Republic and Denmark, and lowest in Ireland and Romania (Table 3). Conclusion After adjustment of LB surveillance data for under-detection, we found a high incidence of symptomatic Bbsl infection in several European countries. Differences in surveillance need to be considered when comparing reported data across countries. Disclosures Frederick Angulo, DVM PhD, Pfizer Vaccines: Employee|Pfizer Vaccines: Stocks/Bonds (Public Company) Gordon Brestrich, PhD, Pfizer Vaccines: Employee|Pfizer Vaccines: Stocks/Bonds (Public Company) Andrew Vyse, Ph.D., Pfizer Vaccines: Employee|Pfizer Vaccines: Stocks/Bonds (Public Company) L. Hannah Gould, PhD, MS, MBA, Pfizer: Employee|Pfizer: Stocks/Bonds (Public Company) Patrick Kelly, PhD, Pfizer Vaccines: Employee|Pfizer Vaccines: Stocks/Bonds (Public Company) Andreas Pilz, PhD, Pfizer Vaccine: Stocks/Bonds (Public Company) Kate Halsby, PhD, Pfizer Vaccines: Stocks/Bonds (Public Company) Jennifer Moisi, PhD, Pfizer: Employee|Pfizer: Stocks/Bonds (Public Company) James H. Stark, PhD, Pfizer: Employee|Pfizer: Stocks/Bonds (Public Company)

Lyme borreliosis (LB), caused by Borrelia burgdorferi sensu lato (Bbsl), is a significant public health concern in Switzerland. Reliable data on seroprevalence and incidence are needed to better understand disease burden and inform prevention strategies. This study aimed to estimate the seroprevalence of Bbsl-specific antibodies and the incidence of symptomatic LB infections in the Swiss adult population.We analyzed Bbsl-specific IgG antibodies in 2,194 residual plasma samples from blood donors (aged 18–75 years) collected at seven Swiss Red Cross donation centers between September and December 2022. Samples were tested using the Liaison® Borrelia IgG VlsE chemiluminescence immunoassay and confirmed with the SeraSpot Anti-Borrelia-10 IgG assay according to National Reference Laboratory interpretative criteria.The overall seroprevalence was 6.1%, with higher prevalence in males (8.2%) than in females (2.9%) and regional variation ranging from 1.6% in Genève to 8.8% in Bern. Based on seroprevalence data, the estimated incidence of symptomatic Bbsl infections was 224 cases per 100,000 population per year (PPY). This estimate, although 1.3 times higher, is similar to the incidence derived from the Sentinella surveillance network. Using Sentinella data, clinically diagnosed erythema migrans was the most common manifestation (150 cases per 100,000 PPY), while disseminated forms, confirmed by clinical and laboratory criteria, occurred less frequently (1.0–8.5 cases per 100,000 PPY).Our findings provide critical insights into the burden of LB in Switzerland, highlight its public health relevance, and reinforce the importance of preventive measures. Future research should focus on longitudinal monitoring and harmonized methodologies to facilitate cross-country comparisons.

Introduction Lyme borreliosis (LB), an infection caused by Borrelia burgdorferi sensu lato (Bbsl), is the most common tick-borne disease in Europe. To further characterize the LB burden in the Czech Republic, we conducted a seroprevalence study and estimated the incidence of symptomatic Bbsl infections. Methods Anti-Bbsl IgM and IgG antibodies were detected in sera collected from the adult population in 2011−2012 by enzyme-linked immunosorbent assay and immunoblot tests at the National Reference Laboratory. The incidence of symptomatic Bbsl infections was estimated from the seroprevalence results and the symptomatic proportion and duration of persistence of anti-Bbsl IgG antibodies in Bbsl-infected individuals. Surveillance under-detection of symptomatic Bbsl infections was estimated by comparing surveillance-reported and seroprevalence-based incidence. Results Samples from 1,996 adults were tested; the median age (range) was 45 (18−87) years; 1,037 (52.0%) were female. The prevalence (with 95% confidence interval) of anti-Bbsl IgG, and IgM and/or IgG (IgM/IgG) antibodies was 6.3% (5.3−7.5%), and 9.5% (8.3−10.9%), respectively. The IgM/IgG prevalence was 7.8% (6.5−9.2%) in Bohemia and 15.3% (12.2−19.0%) in Moravia. There were an estimated 30,563 (26,550−34,962) symptomatic incident Bbsl infections in adults in the Czech Republic in 2012, for an incidence of 352.2 (306.0−402.9) symptomatic Bbsl infections per 100,000 adults per year. There were an estimated 11 (10−13) symptomatic Bbsl infections for each surveillance-reported LB case in the Czech Republic in 2012. Conclusions There is high incidence of symptomatic Bbsl infections in the Czech Republic, particularly in Moravia. Interventions are needed to address the substantial burden of LB in the Czech Republic.

Objectives:Tick-borne encephalitis (TBE), a potentially life-threatening disease caused by the TBE virus, is an emerging European public health threat. TBE is endemic nationwide in Estonia, Latvia, and Lithuania, which have the highest TBE incidence in Europe. TBE vaccination is recommended for all Baltic residents ≥1 year of age, but estimates of the public health impact of TBE vaccination are limited. Methods:TBE vaccination histories were determined for surveillance-reported TBE cases and for respondents from general population surveys conducted in 2019-2023. Vaccine effectiveness (VE) of ≥3 TBE doses administered in accordance with the vaccination schedule (i.e., fully vaccinated) was determined by comparing the proportion of TBE cases who were fully vaccinated (PCV) with the proportion of survey respondents fully vaccinated (PPV), using the screening method formula: VE = 1-[PCV/(1-PCV)]/[PPV/(1-PPV)]. Results:There were 4,361 surveillance-reported TBE cases in the Baltic in 2019-2023; 3,806 (87.3%) were hospitalized, and 30 (0.8%) hospitalized cases died. Of 4,138 surveillance-reported TBE cases with a known TBE vaccination history, 98.3% were unvaccinated, 1.4% partially vaccinated, and 0.3% fully vaccinated. There were 89,656 participants in the general population surveys; of the 80,970 with a known TBE vaccination history, 50.1% were unvaccinated, 29.8% partially vaccinated, and 20.1% fully vaccinated. VE against TBE was 97.4% (93.0-99.0) in Estonia, 99.0% (97.7-99.5) in Latvia, and 99.6% (95% CI 98.8-99.9) in Lithuania. TBE vaccination averted an estimated 3,520 TBE cases in the Baltic in 2019-2023. Conclusions:TBE vaccination in Estonia, Latvia, and Lithuania was highly effective in preventing TBE. To prevent life-threatening TBE, TBE vaccine uptake and compliance with vaccination recommendations should be increased in the Baltic countries.