Lyme borreliosis (LB), the most common tick-borne disease in Europe, is endemic to Poland. Despite public health surveillance with mandatory reporting of LB cases by physicians and laboratories, many symptomatic LB cases are not included in surveillance in Poland. We estimated the extent of the under-ascertainment of symptomatic LB cases via surveillance in the Polish province of Lublin to better understand Poland’s LB burden. The number of incident symptomatic LB cases in Lublin in 2010 was estimated from two seroprevalence studies conducted among adults in Lublin, as well as estimates of the proportion of asymptomatic LB cases and the duration of LB antibody persistence. The estimated number of incident symptomatic LB cases was compared to the number of surveillance-reported cases in Lublin to derive an under-ascertainment multiplier. This multiplier was applied to the number of surveillance-reported cases in 2021 to estimate the number and population-based incidence of symptomatic LB cases in Lublin in 2021. We estimate that there are 5.9 symptomatic LB cases for every surveillance-reported LB case in Lublin. Adjusting for under-ascertainment, the estimated number of symptomatic LB cases in Lublin in 2021 was 6204 (population-based incidence: 467.6/100,000). After adjustment for under-ascertainment, the incidence of symptomatic LB in Lublin, Poland, is high.

Lyme borreliosis (LB), the most common tick‐borne disease in Europe, is endemic to southern coastal Norway. LB commonly presents as erythema migrans, which can disseminate, resulting in more severe disease such as Lyme neuroborreliosis or arthritis. In Norway, public health LB surveillance is conducted via mandatory reporting of laboratory‐confirmed disseminated cases. From 2012 to 2022, Norway's surveillance‐reported incidence of laboratory‐confirmed disseminated LB increased by 78%. Although surveillance provides estimates of the incidence of disseminated LB, this study sought to estimate the incidence of symptomatic LB to better understand Norway's LB disease burden. Two studies were identified that, when combined, estimated an LB seroprevalence of 6.8% in the general adult population in southern Norway. Utilizing data from these seroprevalence studies, public health surveillance, and results from literature searches indicating that 37% of seroconverted LB cases are symptomatic and that the duration of LB antibody detection ranges from 10 to 20 years, we estimated that there were 315–630 symptomatic LB cases per 100,000 adult population in five southern coastal counties in Norway in 2022 and 24–48 cases of symptomatic LB for every public health surveillance‐reported LB case in adults in these five counties in Norway.

Background: Lyme borreliosis (LB) is the most common vector-borne disease in Europe. Research on factors that shape LB risk perception in Europe is limited. This study explores the potential drivers of LB risk perception in the general adult (18–65 years) population of twenty European countries, such as urbanicity, socioeconomic status, dog ownership, gender, age, and tick and LB diagnosis history. Methods: Data were obtained from a 2022 survey of 28,034 adults aged 18–65 years in twenty European countries. The survey included questions on knowledge, attitudes, and practices related to ticks and LB. Respondents were categorized into three income levels (low, middle, or high) based on country-specific income tertiles. Descriptive statistics were calculated, and differences in responses to survey items by income level were assessed using chi-square tests. Risk perception was measured from a survey question asking respondents to rate their risk of contracting LB on a five-point scale from “very low risk” to “very high risk.” Ordinal logistic regression modeled the relationship between predictor variables and LB risk perception. Results: Having a past LB diagnosis (adjusted odds ratio [AOR]: 3.96, 95% confidence interval [CI]: 3.38–4.64) was most strongly tied to increased LB risk perception. Knowing someone with a past LB diagnosis or having a past tick bite, were also significantly associated with higher risk perception (AOR: 2.11, 95% CI: 1.97–2.27, and AOR: 1.71, 95% CI: 1.60–1.84, respectively). High-income respondents were most likely to report a past tick bite (55.4%, 95% CI: 53.5–57.3%) and a past LB diagnosis (13.5%, 95% CI: 12.1–14.8%). Conclusions: Experience with ticks and LB (i.e., via bites or diagnoses) may play a key role in shaping LB risk perception among European adults. Dog ownership and demographic factors such as gender and age may also influence LB risk perception. These results could help LB educational campaigns addressing knowledge and perception gaps.

Diagnosis of Lyme borreliosis (LB) is prone to under ascertainment with the true extent of infection unknown. Cross sectional age-stratified population-based serological survey data may provide insight into this issue. Using data from a previously published Dutch seroprevalence study, we describe the application of catalytic models to make estimates of the annual extent of LB infection. A common assumption when using catalytic models is that IgG is protective and immunity is lifelong. However, human IgG produced in response to natural LB infection does not protect against subsequent infection and its duration may be limited. Individuals were thus assumed to be continually susceptible to LB infection, with a range of scenarios used that varied the length of time that IgG may remain detectable, from 5 years post-infection to lifelong. The possibility that IgG may remain detectable for longer in adults than in children was also explored. Estimates for the annual number of LB infections occurring in the Dutch population ranged from 163,265 (95%CI 130,150–201,723) when assuming IgG remains detectable for only 5 years post-infection to 26,209 (95%CI 17,159–36,557) when assuming IgG is lifelong.