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Background Yersiniosis is one of the most common food-borne zoonoses in Europe, but there are large variations in the reported incidence between different countries. Aim We aimed to describe the trends and epidemiology of laboratory-confirmed Yersinia infections in England and estimate the average annual number of undiagnosed Yersinia enterocolitica cases, accounting for under-ascertainment. Methods We analysed national surveillance data on Yersinia cases reported by laboratories in England between 1975 and 2020 and enhanced surveillance questionnaires from patients diagnosed in a laboratory that has implemented routine Yersinia testing of diarrhoeic samples since 2016. Results The highest incidence of Yersinia infections in England (1.4 cases per 100,000 population) was recorded in 1988 and 1989, with Y. enterocolitica being the predominant species. The reported incidence of Yersinia infections declined during the 1990s and remained low until 2016. Following introduction of commercial PCR at a single laboratory in the South East, the annual incidence increased markedly (13.6 cases per 100,000 population in the catchment area between 2017 and 2020). There were notable changes in age and seasonal distribution of cases over time. The majority of infections were not linked to foreign travel and one in five patients was admitted to hospital. We estimate that around 7,500 Y. enterocolitica infections may be undiagnosed in England annually. Conclusions Findings suggest a considerable number of undiagnosed yersiniosis cases in England, with possibly important changes in the epidemiology. The apparently low incidence of yersiniosis in England is probably due to limited laboratory testing.

OBJECTIVE Irregular menstrual cycles are associated with increased cardiovascular mortality. Polycystic ovary syndrome (PCOS) is characterized by androgen excess and irregular menses; androgens are drivers of increased metabolic risk in women with PCOS. Combined oral contraceptive pills (COCPs) are used in PCOS both for cycle regulation and to reduce the biologically active androgen fraction. We examined COCP use and risk of dysglycemia (prediabetes and type 2 diabetes) in women with PCOS. RESEARCH DESIGN AND METHODS Using a large U.K. primary care database (The Health Improvement Network [THIN]; 3.7 million patients from 787 practices), we carried out a retrospective population-based cohort study to determine dysglycemia risk (64,051 women with PCOS and 123,545 matched control subjects), as well as a nested pharmacoepidemiological case-control study to investigate COCP use in relation to dysglycemia risk (2,407 women with PCOS with [case subjects] and without [control subjects] a diagnosis of dysglycemia during follow-up). Cox models were used to estimate the unadjusted and adjusted hazard ratio, and conditional logistic regression was used to obtain adjusted odds ratios (aORs). RESULTS The adjusted hazard ratio for dysglycemia in women with PCOS was 1.87 (95% CI 1.78–1.97, P < 0.001; adjustment for age, social deprivation, BMI, ethnicity, and smoking), with increased rates of dysglycemia in all BMI subgroups. Women with PCOS and COCP use had a reduced dysglycemia risk (aOR 0.72, 95% CI 0.59–0.87). CONCLUSIONS In this study, limited by its retrospective nature and the use of routinely collected electronic general practice record data, which does not allow for exclusion of the impact of prescription-by-indication bias, women with PCOS exposed to COCPs had a reduced risk of dysglycemia across all BMI subgroups. Future prospective studies should be considered for further understanding of these observations and potential causality.

ObjectiveTo investigate the impact on child health up to age 5 years of a policy to use antibiotic prophylaxis for caesarean section before incision compared with after cord clamping.DesignObservational controlled interrupted time series study.SettingUK primary and secondary care.Participants515 945 children born in 2006-18 with linked maternal records and registered with general practices contributing to two UK primary care databases (The Health Improvement Network and Clinical Practice Research Datalink), and 7 147 884 children with linked maternal records in the Hospital Episode Statistics database covering England, of which 3 945 351 were linked to hospitals that reported the year of policy change to administer prophylactic antibiotics for caesarean section before incision rather than after cord clamping.InterventionFetal exposure to antibiotics shortly before birth (using pre-incision antibiotic policy as proxy) compared with no exposure.Main outcome measuresThe primary outcomes were incidence rate ratios of asthma and eczema in children born by caesarean section when pre-incision prophylactic antibiotics were recommended compared with those born when antibiotics were administered post-cord clamping, adjusted for temporal changes in the incidence rates in children born vaginally.ResultsProphylactic antibiotics administered before incision for caesarean section compared with after cord clamping were not associated with a significantly higher risk of asthma (incidence rate ratio 0.91, 95% confidence interval 0.78 to 1.05) or eczema (0.98, 0.94 to 1.03), including asthma and eczema resulting in hospital admission (1.05, 0.99 to 1.11 and 0.96, 0.71 to 1.29, respectively), up to age 5 years.ConclusionsThis study found no evidence of an association between pre-incision prophylactic antibiotic use and risk of asthma and eczema in early childhood in children born by caesarean section.

BackgroundGestational diabetes mellitus (GDM) affects over 4% of pregnancies in England. We investigated GDM epidemiology within ethnically diverse population and the current offer of services to women with previous GDM to reduce their type 2 diabetes mellitus (T2DM) risk.Methods(i) Analysis of routinely collected maternity data examining GDM incidence and risk factors; (ii) local authority self-assessment questionnaire on public health interventions targeting women with previous GDM and (iii) service development discussions regarding the current pathway and areas for improvement.ResultsOf 9390 births between 2014 and 2018, 6.8% had a record of GDM. High body mass index (BMI), maternal age, and ethnicity (South Asian and some mixed ethnic backgrounds) were independent predictors of GDM. There were no public health commissioned services specifically targeting women with previous GDM. Weaknesses in transition from secondary to primary care and areas for improvement when screening for GDM were identified.ConclusionsGDM burden in this population was high. Awareness should be raised on the importance of regular glucose testing and lifestyle modification to delay or prevent progression to T2DM, particularly within high risk groups. The potential for health visitors to contribute to this should be explored. Commissioners should review evidence to develop a flexible lifestyle services model to meet the specific needs of these women.

There is a gap in the literature investigating the impact of obstetric complications on subsequent mental ill health outcomes. The aim of this study was to establish the association between post-partum haemorrhage (PPH) and mental ill health. We conducted a retrospective open cohort study utilizing linked primary care (The Health Improvement Network (THIN)) and English secondary care (Hospital Episode Statistics (HES)) databases, from January 1, 1990 to January 31, 2018. A total of 42,327 women were included: 14,109 of them were exposed to PPH during the study period and 28,218 unexposed controls were matched for age and date of delivery. Hazard ratios (HRs) for mental illness among women with and without exposure to PPH were estimated after controlling for covariates. Women who had had PPH were at an increased risk of developing postnatal depression (adjusted HR: 1·10, 95%CI: 1·01–1·21) and post–traumatic stress disorder (PTSD) (adjusted HR: 1·17, 95%CI: 0·73–1·89) compared to women unexposed to PPH. When restricting the follow–up to the first year after childbirth, the adjusted HR for PTSD was 3·44 (95% CI 1·31–9·03). No increase in the overall risk was observed for other mental illnesses, including depression (adjusted HR: 0·94, 95%CI: 0·87–1·01), severe mental illness (adjusted HR: 0·65, 95%CI: 0·40–1·08, p = 0·239) and anxiety (adjusted HR: 0·99, 95%CI: 0·90–1·09). PPH is associated with a significant increase in the risk of developing postnatal depression and PTSD in the first year after delivery. Active monitoring for mental illness should form an integral part of the follow–up in women who suffered a PPH.

ObjectiveTo explore whether thyroid stimulating hormone (TSH) concentration in patients with a diagnosis of hypothyroidism is associated with increased all cause mortality and a higher risk of cardiovascular disease and fractures.DesignRetrospective cohort study.SettingThe Health Improvement Network (THIN), a database of electronic patient records from UK primary care.ParticipantsAdult patients with incident hypothyroidism from 1 January 1995 to 31 December 2017.ExposureTSH concentration in patients with hypothyroidism.Main outcome measuresIschaemic heart disease, heart failure, stroke/transient ischaemic attack, atrial fibrillation, any fractures, fragility fractures, and mortality. Longitudinal TSH measurements from diagnosis to outcomes, study end, or loss to follow-up were collected. An extended Cox proportional hazards model with TSH considered as a time varying covariate was fitted for each outcome.Results162 369 patients with hypothyroidism and 863 072 TSH measurements were included in the analysis. Compared with the reference TSH category (2-2.5 mIU/L), risk of ischaemic heart disease and heart failure increased at high TSH concentrations (>10 mIU/L) (hazard ratio 1.18 (95% confidence interval 1.02 to 1.38; P=0.03) and 1.42 (1.21 to 1.67; P10 mIU/L. An increase in the risk of fragility fractures was observed in patients in the highest TSH category (>10 mIU/L) (hazard ratio 1.15 (1.01 to 1.31; P=0.03)).ConclusionsIn patients with a diagnosis of hypothyroidism, no evidence was found to suggest a clinically meaningful difference in the pattern of long term health outcomes (all cause mortality, atrial fibrillation, ischaemic heart disease, heart failure, stroke/transient ischaemic attack, fractures) when TSH concentrations were within recommended normal limits. Evidence was found for adverse health outcomes when TSH concentration is outside this range, particularly above the upper reference value.

Objectives To investigate the association of birthweight percentile with cord blood glucose, lipids, and insulin levels. Study design Data obtained from 1522 newborns were included in the Born in Guangzhou Cohort study. The generalized additive model and multivariable linear regression model were used to explore the nonlinear and linear relationships between birthweight and cord blood metabolic measures, and to evaluate the differences of metabolic measures Z-scores among small for gestational age, appropriate for gestational age, and large for gestational age babies. Results Birthweight Z-score was linearly associated with increased cord blood insulin Z-score (adjusted β = 0.30; 95% CI, 0.22-0.37). Compared with appropriate for gestational age babies, neonates born small for gestational age had significantly higher cord blood triglycerides Z-score (adjusted mean difference [MDadj], 0.60; 95% CI, 0.40-0.79) and lower cord blood insulin (MDadj, −0.37; 95% CI, −0.57 to −0.16), high-density lipoprotein cholesterol (MDadj, −0.34; 95% CI, −0.55 to −0.13), total cholesterol (MDadj, −0.26; 95% CI, −0.47 to −0.05), and low-density lipoprotein (MDadj, −0.23; 95% CI, −0.43 to −0.02) Z-scores, and neonates born large for gestational age had higher cord blood insulin Z-score (MDadj, 0.31; 95% CI, 0.09 to 0.52). Conclusions Our findings support the hypothesis that babies born small for gestational age and large for gestational age are exposed to different intrauterine environments, which may contribute to altered fat accumulation patterns with implications for the risk of metabolic dysfunction later in life. There is a need to consider the development of tailored intervention strategies to prevent metabolic dysfunction in adult life for these babies.

ContextMortality and infection-related hospital admissions are increased in patients with primary adrenal insufficiency (PAI). However, the risk of primary care-managed infections in patients with PAI is unknown.ObjectiveTo estimate infection risk in PAI due to Addison’s disease (AD) and congenital adrenal hyperplasia (CAH) in a primary care setting.DesignRetrospective cohort study using UK data collected from 1995 to 2018.Main outcome measuresIncidence of lower respiratory tract infections (LRTIs), urinary tract infections (UTIs), gastrointestinal infections (GIIs), and prescription counts of antimicrobials in adult PAI patients compared to unexposed controls.ResultsA diagnosis of PAI was established in 1580 AD patients (mean age 51.7 years) and 602 CAH patients (mean age 35.4 years). All AD patients and 42% of CAH patients were prescribed glucocorticoids, most frequently hydrocortisone in AD (82%) and prednisolone in CAH (50%). AD and CAH patients exposed to glucocorticoids, but not CAH patients without glucocorticoid treatment, had a significantly increased risk of LRTIs (adjusted incidence rate ratio AD 2.11 [95% confidence interval 1.64-2.69], CAH 3.23 [1.21-8.61]), UTIs (AD 1.51 [1.29-1.77], CAH 2.20 [1.43-3.34]), and GIIs (AD 3.80 [2.99-4.84], CAH 1.93 [1.06-3.52]). This was mirrored by increased prescription of antibiotics (AD 1.73 [1.69-1.77], CAH 1.77 [1.66-1.89]) and antifungals (AD 1.89 [1.74-2.05], CAH 1.91 [1.50-2.43]).ConclusionsThere is an increased risk of infections and antimicrobial use in PAI in the primary care setting at least partially linked to glucocorticoid treatment. Future studies will need to address whether more physiological glucocorticoid replacement modes could reduce this risk.PrécisUsing data from 1580 AD patients and 602 CAH patients collected in a UK primary care database from 1995 to 2018, we identified increased risk of infections and antimicrobial prescription counts.

Context Mortality and infection-related hospital admissions are increased in patients with primary adrenal insufficiency (PAI). However, the risk of primary care–managed infections in patients with PAI is unknown. Objective To estimate infection risk in PAI due to Addison’s disease (AD) and congenital adrenal hyperplasia (CAH) in a primary care setting. Design Retrospective cohort study using UK data collected from 1995 to 2018. Main outcome measures Incidence of lower respiratory tract infections (LRTIs), urinary tract infections (UTIs), gastrointestinal infections (GIIs), and prescription counts of antimicrobials in adult PAI patients compared to unexposed controls. Results A diagnosis of PAI was established in 1580 AD patients (mean age 51.7 years) and 602 CAH patients (mean age 35.4 years). All AD patients and 42% of CAH patients were prescribed glucocorticoids, most frequently hydrocortisone in AD (82%) and prednisolone in CAH (50%). AD and CAH patients exposed to glucocorticoids, but not CAH patients without glucocorticoid treatment, had a significantly increased risk of LRTIs (adjusted incidence rate ratio AD 2.11 [95% confidence interval (CI) 1.64–2.69], CAH 3.23 [95% CI 1.21–8.61]), UTIs (AD 1.51 [95% CI 1.29–1.77], CAH 2.20 [95% CI 1.43–3.34]), and GIIs (AD 3.80 [95% CI 2.99–4.84], CAH 1.93 [95% CI 1.06–3.52]). This was mirrored by increased prescription of antibiotics (AD 1.73 [95% CI 1.69–1.77], CAH 1.77 [95% CI 1.66–1.89]) and antifungals (AD 1.89 [95% CI 1.74–2.05], CAH 1.91 [95% CI 1.50–2.43]). Conclusions There is an increased risk of infections and antimicrobial use in PAI in the primary care setting at least partially linked to glucocorticoid treatment. Future studies will need to address whether more physiological glucocorticoid replacement modes could reduce this risk.

Aims Non-Alcoholic Fatty Liver Disease (NAFLD) is one of the leading causes of liver transplantation in the West. This study seeks to examine whether women with gestational diabetes mellitus (GDM) are at increased risk of developing NAFLD compared to women without GDM. Methods We conducted a population-based retrospective matched-controlled cohort study utilising The Health Improvement Network (THIN), a large primary care database representative of the United Kingdom population, between 01/01/1990 to 31/05/2016 followed by systematic review of available literature. The study population included 9640 women with GDM and 31,296 controls without GDM, matched for age, body mass index (BMI) and time of pregnancy. All study participants were free from NAFLD diagnosis at study entry. Patients with GDM and patients developing NAFLD were identified by clinical codes. Results The median (range) follow-up duration was similar in women with and without GDM (2.95 (1.21–6.01) vs 2.85 (1.14–5.75) years respectively). Unadjusted incidence rate ratio (IRR) for NAFLD development in women with vs without GDM was 3.28 (95% CI 2.14–5.02), which remained significant after adjustment for wide range of potential confounders (IRR 2.70; 95% CI 1.744–4.19). The risk of NAFLD in GDM remained high (IRR 2.46: 95% CI 1.51–4.00) despite women being censored after they developed type 2 diabetes. The meta-analysis of 3 studies (including the current study) showed increased NAFLD risk in women with vs without GDM (OR 2.60; 95% CI 1.90–3.57, I2 = 0%). As our study is based on routine clinical diagnosis of NAFLD, this study could potentially have underestimated the risk of NAFLD development. Conclusions Women with GDM are at increased risk of developing NAFLD in their later life compared to women without GDM regardless of the development of type 2 diabetes. Clinicians should have a low threshold to investigate women with history of GDM for the presence of NAFLD. Further studies to identify screening strategies are needed.

BackgroundNeither the incidence of indications for childhood tonsillectomy nor the proportion of tonsillectomies that are evidence-based is known.AimTo determine the incidence of indications for tonsillectomy in UK children, and the proportion of tonsillectomies meeting evidence-based criteria.Design and settingA retrospective cohort study of electronic medical records of children aged 0–15 years registered with 739 UK general practices contributing to a research database.MethodChildren with recorded indications for tonsillectomy were identified from electronic medical records. Evidence-based indications included documented sore throats of sufficient frequency and severity (Paradise criteria); periodic fever, aphthous stomatitis, pharyngitis, and cervical adenitis syndrome (PFAPA); or tonsillar tumour. Other indications were considered non-evidence-based. The numbers of children subsequently undergoing tonsillectomy was then identified. The numbers with evidence-based and non-evidence-based indications for surgery among children who had undergone tonsillectomy were determined.ResultsThe authors included 1 630 807 children followed up for 7 200 159 person–years between 2005 and 2016. Incidence of evidence-based indications for tonsillectomy was 4.2 per 1000 person years; 13.6% (2144/15 760) underwent tonsillectomy. Incidence of childhood tonsillectomy was 2.5 per 1000 person years; 11.7% (2144/18 281) had evidence-based indications, almost all with Paradise criteria. The proportion of evidence-based tonsillectomies was unchanged over 12 years. Most childhood tonsillectomies followed non-evidence-based indications: five to six sore throats (12.4%) in 1 year, two to four sore throats (44.6%) in 1 year, sleep disordered breathing (12.3%), or obstructive sleep apnoea (3.9%).ConclusionIn the UK, few children with evidence-based indications undergo tonsillectomy and seven in eight of those who do (32 500 of 37 000 annually) are unlikely to benefit.

Background Maternity services should take into account the needs of all women, including those related to disability. No reliable information, however, exists on the extent and characteristics of disability in this population in the UK. This brief report provides an overview of the prevalence of disability in women giving birth in the UK as measured by the presence of a limiting longstanding illness (LLI). The demographic, socio-economic, lifestyle and pregnancy related characteristics and child health outcomes are summarised to inform maternity and postnatal care service planning, and policy development. Methods Secondary analysis of data on 18,231 mother-child pairs from the nationally representative UK Millennium Cohort Study. The baseline interviews with families were carried out in 2001-2002. The LLI prevalence in women who had recently delivered was estimated, and relevant characteristics and differences in outcomes compared using descriptive statistics taking into account the study design and non-response. Results 9.4% (95% CI 8.7-10.0) of women who had recently given birth reported having an LLI. Musculoskeletal, respiratory and mental disorders accounted for most of the health problems. A significantly higher proportion of women with an LLI received means-tested financial benefits, had no educational qualifications and suffered from intimate partner violence compared to women who did not have an LLI (49.3% vs 35.3%, 20.4% vs 15.0%, 6.0% vs 3.3%, respectively). They were also more likely to smoke throughout pregnancy than women without an LLI (29.2% vs 20.8%), have a preterm birth (10.9% vs 6.8%) and be lone parents (19.5% vs 13.9%). Only 25.6% of children of mothers with an LLI were breastfed for more than three months compared to 33.4% of infants of mothers who did not have an LLI. At the age of seven years, 12.0% of children of mothers with an LLI had an activity limiting health problem themselves compared to 6.2% of children of mothers without an LLI. Conclusions Disability in women who had recently delivered is relatively common. It is associated with social and economic inequalities and worse pregnancy and child related outcomes. Apart from condition-specific support during and after pregnancy, disabled women may require extra help from health professionals to quit smoking, continue breastfeeding, and reduce intimate partner violence.

This paper presents preliminary results in our investigations of the biological (abiotic and biotic) and non-biological causes of the spatial heterogeneity and temporal change of tick-borne encephalitis (TBE), both within and between Estonia, Latvia, and Lithuania. Spatial analysis revealed that the land cover and precise seasonal patterns of climatic indices (temperature and normalized difference vegetation index) can explain 55% of the observed spatial variation in TBE incidence over the period 1993–98 across all the Baltic States. Temporal analysis of climatic variables indicates a very specific change in spring temperature conditions from 1993 onwards that could enhance the transmission of TBE virus. Further time series analysis of climate, together with analysis of biotic factors, socio-economic conditions, and human behaviour is being undertaken to explain the epidemiological patterns more fully.

Objective To explore the association between maternal disability as measured by the presence of a limiting longstanding illness (LLI) 9 months postpartum and subsequent child health at the age of 7 years. Design Nationally representative prospective longitudinal study. Setting England, Scotland, Wales and Northern Ireland. Participants Secondary analysis of data on 11 807 mother–child pairs recruited to the UK Millennium Cohort Study. Baseline interviews with mothers were carried out in 2001–2002. When the children were 7 years old, the follow-up survey included questions about limiting longstanding health conditions in the child. Primary outcome measure Any longstanding condition that was reported to limit the children9s activities in any way. Results Nearly 7% of all children were reported to have an LLI at the age of 7 years. The majority (88.1%, 95% CI 85.6% to 90.2%) of children whose mother was disabled did not have an LLI themselves. The children of disabled mothers, however, had higher odds of LLI (OR=1.9, 95% CI 1.5 to 2.5) independently of different maternal, pregnancy and birth characteristics and breast feeding duration. Inclusion of poverty measures in the model did not significantly affect the odds (OR=1.8, 95% CI 1.4 to 2.4), suggesting that maternal LLI around the time of birth increases the odds of child LLI at the age of 7 years independently of starting life in poverty. Conclusions There is a strong positive association between maternal and child LLI. Health professionals should work together with social care and other relevant service providers to identify the individual needs of disabled parents and provide adequate support throughout the pregnancy and after the child is born. Further research is important to clarify the exact nature of the associations for different types of maternal and child disability.

Although the presence of tick-borne encephalitis (TBE) virus circulating in tick populations depends on large-scale patterns of climate, and the local density of infected ticks depends on the abundance of mammalian hosts, the risk of human infection depends on the access and use by human populations of tick-infested habitats, particularly forests, at the landscape level. We investigated the incidence of reported TBE cases in rural parishes (i.e., municipalities) in Latvia. The following major characteristics of parishes were considered: whether their environment is suitable for tick and tick-host populations (depending on land cover); whether the local human population is likely to enter the forest on a regular base (depending on land use); and whether the spatial distributions of these two aspects are likely to intersect, through access rules (as a function of land ownership). The results indicated that all three aspects are important in explaining and predicting the spatial distribution of TBE cases in the rural areas of Latvia. The concept of landscape is here given new depth by consideration of its physical structure, its use by human populations, and its accessibility as modulated by ownership.

Tick-borne encephalitis (TBE) incidence increased markedly in the Baltics and Slovenia in the early 1990s, but then declined again in some places. Our analyses of temporal and spatial data on TBE incidence and vaccination revealed that over 1970-2005 up-take of vaccination varied in both time and space according to incidence, i.e. was apparently responsive to perceived risk. Since 1999, however, decreases in incidence in many counties within each country have far exceeded vaccination rates or immunity through natural exposure, and in Latvia and Lithuania these changes are correlated with previous incidence. Survey data on human activities in Latvia revealed that people in socio-economic groups whose behaviour put them at highest risk of exposure to ticks in forests, including people with lower education and lowest incomes, are least likely to be vaccinated. We conclude that risk avoidance through changing human behaviour has driven incidence-dependent decreases in TBE infection, but targeted vaccination campaigns could provide more secure protection.

Tick-borne encephalitis (TBE), the most serious widespread vector-borne disease of humans in Europe, increased from 2- to 30-fold in many Central and Eastern European countries from 1992 to 1993, coinciding with independence from Soviet rule. Unemployment and low income have been shown in Latvia to be statistically associated with high-risk behaviour involving harvest of wild foods from tick-infested forests, and also with not being vaccinated against TBE. Archival data for 1970--2005 record major changes in the agricultural and industrial sectors, and consequent changes in the abiotic and biotic environment and socio-economic conditions, which could have increased the abundance of infected ticks and the contact of humans with those ticks. For example, abandoned agricultural fields became suitable for rodent transmission hosts; use of pesticides and emissions of atmospheric industrial pollutants plummeted; wildlife hosts for ticks increased; tick populations appear to have responded; unemployment and inequality increased in all countries. These factors, by acting synergistically but differentially between and within each country, can explain the marked spatio-temporal heterogeneities in TBE epidemiology better than can climate change alone, which is too uniform across wide areas. Different degrees of socio-economic upheaval caused by political transition in Estonia, Latvia, Lithuania, Slovenia and the Czech Republic can apparently explain the marked variation in TBE upsurge. Causal linkage between national socio-economic conditions and epidemiology is strongly indicated by striking correlations across eight countries between the degree of upsurge of TBE and both poverty and household expenditure on food (R2 = 0.533 and 0.716, respectively).

Background. Pathogens transmitted by ticks cause human disease on a greater scale than any other vector-borne infections in Europe, and have increased dramatically over the past 2–3 decades. Reliable records of tick-borne encephalitis (TBE) since 1970 show an especially sharp upsurge in cases in Eastern Europe coincident with the end of Soviet rule, including the three Baltic countries, Estonia, Latvia and Lithuania, where national incidence increased from 1992 to 1993 by 64, 175 and 1,065%, respectively. At the county level within each country, however, the timing and degree of increase showed marked heterogeneity. Climate has also changed over this period, prompting an almost universal assumption of causality. For the first time, we analyse climate and TBE epidemiology at sufficiently fine spatial and temporal resolution to question this assumption. Methodology/Principal Finding. Detailed analysis of instrumental records of climate has revealed a significant step increase in spring-time daily maximum temperatures in 1989. The seasonal timing and precise level of this warming were indeed such as could promote the transmission of TBE virus between larval and nymphal ticks co-feeding on rodents. These changes in climate, however, are virtually uniform across the Baltic region and cannot therefore explain the marked spatio-temporal heterogeneity in TBE epidemiology. Conclusions/Significance. Instead, it is proposed that climate is just one of many different types of factors, many arising from the socio-economic transition associated with the end of Soviet rule, that have acted synergistically to increase both the abundance of infected ticks and the exposure of humans to these ticks. Understanding the precise differential contribution of each factor as a cause of the observed epidemiological heterogeneity will help direct control strategies.

Despite evidence that socio-economic factors associated with political transition played a major causal role in the abrupt upsurge in tick-borne encephalitis (TBE) in the newly independent Baltic States, doubts are still repeatedly expressed about the importance of these factors relative to changes in public health practices that may have affected merely the registration of cases. In response to these doubts, evidence of relevant practices of surveillance, registration, diagnosis, awareness and immunization is presented as taken from archived data and interviews with experienced medical practitioners. There were changes that could have had neutral, negative or positive impacts on recorded TBE incidence, but the variable timing in these changes at both national and regional levels is not consistent with their having been responsible for the epidemiological patterns observed in the early 1990s.