{ "slug": "tick-borne-encephalitis", "question": "What are the odds of getting tick-borne encephalitis (TBE)?", "category": "health", "tags": [ "travel" ], "no_reliable_estimate": false, "perceived": { "description": "Tick-borne encephalitis is the dangerous half of the tick-disease pair, and in Central and Eastern Europe it is consistently overshadowed by the other half. When people in Poland, the Baltic states, or Czechia worry about \"kleszcze\", the named fear is almost always Lyme borreliosis — the bacterial infection that is far more common but, treated early, far less likely to cause lasting harm. TBE is a virus, it can inflame the brain and its lining (meningitis and encephalitis), there is no antiviral treatment, and unlike Lyme it is vaccine-preventable. Yet vaccine uptake across most of the endemic belt outside Austria remains low, which is the clearest signal that the specific, severe, preventable disease is underweighted relative to the diffuse seasonal anxiety about ticks in general.\n", "rough_estimate": "usually folded into a general fear of ticks/Lyme; the specific TBE risk is rarely distinguished, and the vaccine is widely available but underused outside Austria", "kind": "intuition" }, "native": { "display": "~10 in 100,000 per year (unvaccinated adult, high-endemic Central/Eastern European region)", "numerator": 10, "denominator": 100000, "unit": "per year", "population": "unvaccinated adults resident in high-endemic Central/Eastern European foci (Baltic states, Czechia, Slovenia, northeastern Poland)" }, "normalized": { "lifetime_us_adult": 0.006, "display": "~1 in 170 lifetime (unvaccinated adult, high-endemic Central/Eastern Europe)", "log_value": -2.22, "assumptions": "TBE incidence is sharply focal. The EU/EEA average notification rate was 0.81 per 100,000 in 2022 (ECDC), but risk concentrates in a high-endemic belt where rates run an order of magnitude higher: Lithuania reported 13.4 per 100,000 and Estonia 10.5 in 2022, and Czechia, Estonia and Lithuania have each exceeded 5 per 100,000 for five consecutive years. Northeastern Poland (Podlaskie) is a comparably intense focus. A central native estimate of ~10 per 100,000 per year is used for an unvaccinated adult living in this high-endemic belt. Lifetime conversion over the standard 59-year adult horizon: 1 − (1 − 1.0 × 10⁻⁴)^59 ≈ 0.0059, rounded to 0.006 (about 1 in 170). The lower uncertainty bound (0.003) reflects lower-endemicity foci or limited outdoor exposure (~4–5 per 100,000); the upper bound (0.012) reflects the highest national rates combined with heavy outdoor exposure (~20 per 100,000). This figure counts symptomatic, clinically diagnosed TBE; roughly three-quarters of TBE virus infections are asymptomatic (CDC), so the infection rate is several-fold higher than the disease rate stated here. The scope is subgroup_lifetime (a high-endemic European resident); for a US adult, locally acquired TBE risk is effectively zero — only 12 cases have ever been reported among US travelers.\n", "uncertainty": { "low": 0.003, "high": 0.012 }, "scope": "subgroup_lifetime" }, "sources": [ { "url": "https://www.cdc.gov/mmwr/volumes/72/rr/rr7205a1.htm", "title": "Tick-Borne Encephalitis Vaccine: Recommendations of the Advisory Committee on Immunization Practices, United States, 2023", "publisher": "US Centers for Disease Control and Prevention (MMWR Recommendations and Reports)", "source_type": "govt_report", "statistic": "Approximately three-fourths of TBE virus infections are asymptomatic; European-subtype case-fatality is usually <2%; sequelae occur in 20%–40% of European-subtype cases; vaccine effectiveness after ≥3 doses is 91%–99%, with 99% seroconversion after dose 3.", "excerpt": "\"Approximately three fourths of TBE virus infections are asymptomatic. … Among patients with neurologic disease and infected with the European subtype virus, the case fatality rate is usually <2%. … Among patients infected with the European subtype virus, sequelae have been reported in 20%–40% overall, including neurologic sequelae (e.g., limb paresis or paralysis) in up to 10%. … VE estimates for the European subtype virus TBE vaccines against disease caused by the European subtype virus after ≥3 doses of vaccine are 91%–99%. … Among 416 adults seronegative at baseline, 411 (99%) were seropositive at 21–28 days after dose 3.\"\n", "source_date": "2023-11-02", "source_accessed": "2026-06-21", "archive_url": "http://web.archive.org/web/20260511083323/https://www.cdc.gov/mmwr/volumes/72/rr/rr7205a1.htm", "calculation_notes": "Supplies the severity profile (CFR <2%, sequelae 20–40%, asymptomatic fraction ~75%) and the vaccine-efficacy basis for the personal factor multipliers. VE of 91–99% after the full primary series implies a residual risk multiplier of ~0.05× for a fully vaccinated person. The 12-US-traveler figure (1 case in 1979, 11 during 2001–2021) anchors the \"effectively zero for US residents\" framing.\n", "independence_note": "US CDC/ACIP synthesis of vaccine-trial and European-effectiveness data; independent of the ECDC surveillance counts used for incidence.\n" }, { "url": "https://www.ecdc.europa.eu/en/publications-data/tick-borne-encephalitis-annual-epidemiological-report-2022", "title": "Tick-borne encephalitis — Annual Epidemiological Report for 2022", "publisher": "European Centre for Disease Prevention and Control (ECDC)", "source_type": "govt_report", "statistic": "20 EU/EEA countries reported 3,650 TBE cases for 2022 (3,516 confirmed); EU/EEA notification rate 0.81 per 100,000, highest in Lithuania (13.4) and Estonia (10.5); 94.0% of cases with known vaccination status were unvaccinated. Poland reported 367 cases (rate 1.0).", "excerpt": "\"For 2022, 20 EU/EEA countries reported 3 650 cases of tick-borne encephalitis (TBE), 3 516 (96.3%) of which were confirmed. … The EU/EEA notification rate for 2022 was 0.81 per 100 000 population. … The notification rate was highest in Lithuania (13.4 cases per 100 000 population), followed by Estonia (10.5). … Notification rates were consistently high (over five per 100 000 population) during the last five years in three countries: Lithuania, Estonia, and Czechia. … Of the 1 620 confirmed cases for which information about vaccination status was available, 1 522 (94.0%) were reported as not vaccinated against TBE.\"\n", "source_date": "2024-06-01", "source_accessed": "2026-06-21", "archive_url": "http://web.archive.org/web/20260305112417/https://www.ecdc.europa.eu/en/publications-data/tick-borne-encephalitis-annual-epidemiological-report-2022", "calculation_notes": "Provides the population-based incidence anchoring the native rate and the regional breakdown. The EU/EEA average of 0.81 per 100,000 versus the Baltic high-endemic rates of 10–13 per 100,000 (Lithuania historically to 24–25 in 2019–2020; Latvia averaging 8.5 over 2018–2021) establishes the ~10× focal concentration used in the assumptions. Poland's national rate was 1.0 per 100,000 (367 cases) in 2022, but risk concentrates in northeastern foci far above the national average. The 94%-unvaccinated figure among cases with known status anchors the underrated framing and the vaccine factor multiplier.\n", "independence_note": "European surveillance aggregation via EpiPulse/TESSy, independent of the US CDC synthesis and the single-centre Polish hospital series.\n" }, { "url": "https://pmc.ncbi.nlm.nih.gov/articles/PMC12300996/", "title": "Breakthrough Tick-Borne Encephalitis and Epidemiological Trends in an Endemic Region in Poland: A Retrospective Hospital-Based Study, 1988–2020", "publisher": "Vaccines (Basel) — Sulik-Wakulińska, Toczyłowski & Grygorczuk", "source_type": "peer_reviewed", "statistic": "1,518 patients were hospitalised for TBE at a single Białystok hospital over 1988–2020, capturing approximately 50% of all TBE cases reported in the (northeastern Poland) region.", "excerpt": "\"Between 1988 and 2020, a total number of 1518 patients were hospitalized because of TBE [at the study hospital, which captures] approximately 50% of all TBE cases reported in the region. … Tick-borne encephalitis is endemic across much of Eurasia, [with] northeastern Poland [a] highly endemic area.\"\n", "source_date": "2025-06-20", "source_accessed": "2026-06-21", "archive_url": "https://web.archive.org/web/20260622052849/https://pmc.ncbi.nlm.nih.gov/articles/PMC12300996/", "calculation_notes": "Confirms northeastern Poland (Podlaskie) as a high-endemic focus comparable to the Baltic belt, supporting its inclusion in the native population definition and the Polish regional_breakdown row. The single-centre series capturing ~50% of regional cases illustrates the focal clustering that the national-average rates obscure.\n", "independence_note": "Peer-reviewed single-centre Polish cohort, independent of both the ECDC aggregate counts and the US CDC recommendations.\n" } ], "comparison_anchors": [ { "label": "Lyme disease (lifetime, endemic-region adult)", "lifetime_us_adult": 0.25 }, { "label": "Melanoma from UV exposure (lifetime, US adult)", "lifetime_us_adult": 0.028 }, { "label": "Death in a car crash (lifetime, US)", "lifetime_us_adult": 0.0108 }, { "label": "Rabies death from a dog bite (lifetime, global adult)", "lifetime_us_adult": 0.00069 } ], "regional_breakdown": [ { "region": "Lithuania / Estonia (per year, highest EU national rates)", "probability": 0.00013, "notes": "ECDC 2022: Lithuania 13.4 and Estonia 10.5 per 100,000 — the highest reported national notification rates in the EU/EEA. Lithuania reached 24–25 per 100,000 in 2019–2020." }, { "region": "Czechia / Slovenia / Latvia (per year, high-endemic)", "probability": 0.00007, "notes": "ECDC 2022: Czechia 6.7 and Slovenia 5.9 per 100,000; Latvia averaged 8.5 per 100,000 over 2018–2021 (did not report 2022). Local foci run higher than these national averages." }, { "region": "Poland (national, per year)", "probability": 0.00001, "notes": "ECDC 2022: 367 cases, national rate 1.0 per 100,000. Risk concentrates sharply in northeastern foci (Podlaskie), where a single Białystok hospital captures ~50% of the region's cases — well above the national average." }, { "region": "EU/EEA average (per year, all countries)", "probability": 0.0000081, "notes": "ECDC 2022 average notification rate 0.81 per 100,000 — an order of magnitude below the high-endemic belt because risk is sharply focal." }, { "region": "United States (locally acquired, per year)", "probability": 3e-10, "notes": "Effectively zero. Only 12 TBE cases have ever been reported among US travelers (1 in 1979, 11 during 2001–2021); there is no established local transmission." } ], "personal_factor_multipliers": [ { "factor": "Full TBE vaccination (≥3-dose primary series, boosters up to date)", "multiplier": 0.05, "notes": "CDC ACIP 2023: vaccine effectiveness against European-subtype disease is 91–99% after ≥3 doses, with 99% seroconversion after the third dose. Residual risk ≈ 0.05×. This is by far the dominant lever — and the one most often left unused outside Austria." }, { "factor": "Incomplete or lapsed TBE vaccination (1–2 doses, or booster overdue)", "multiplier": 0.3, "notes": "Two doses confer roughly one season of protection; durable, high-level protection requires the full three-dose primary series plus periodic boosters (CDC ACIP 2023)." }, { "factor": "Frequent outdoor activity in endemic forest foci (forestry work, foraging, mushroom-picking, hiking)", "multiplier": 3, "notes": "TBE risk concentrates in people with heavy questing-tick exposure through vegetation during the April–November season; ~90% of EU cases occur June–November." }, { "factor": "Resident of lower-endemicity Western/Southern Europe or a non-endemic region", "multiplier": 0.2, "notes": "TBE is sharply focal; the EU/EEA average rate (0.81 per 100,000) is roughly an order of magnitude below the Baltic/Czech high-endemic belt, and much of Western and Southern Europe is near zero (ECDC 2022)." } ], "short_label": "Tick-borne encephalitis", "myth_framing": "underrated", "outcome_severity": "serious_harm", "exposure_pattern": "recurring", "outcome_type": "serious_permanent_harm", "valence": "negative", "caveats": "The 1-in-170 figure is the lifetime probability of symptomatic, clinically diagnosed TBE for an unvaccinated adult living in a high-endemic Central or Eastern European focus; it is not a US-resident figure and not an all-of-Europe figure. Roughly three-quarters of TBE virus infections are asymptomatic, so the infection rate is several times higher than the disease rate stated here, while the rate of severe neuroinvasive disease is lower. Two facts make TBE behave differently from Lyme borreliosis, with which it is usually confused. First, the virus sits in the tick's salivary glands and can transmit within minutes of attachment, so prompt tick removal — highly protective against Lyme, which needs 36+ hours of attachment — does little against TBE; vaccination is the primary countermeasure. Second, TBE has an alimentary route Lyme lacks: drinking unpasteurized milk or eating fresh cheese from infected goats, sheep, or cows has caused documented family and village outbreaks. Severity rises with age. For the European subtype the case-fatality rate is usually under 2%, but lasting sequelae are reported in 20–40% of symptomatic cases and persistent neurologic deficits in up to 10%; most patients nonetheless recover fully. The Far Eastern subtype circulating in Russia and parts of Asia is substantially more severe (case-fatality up to 20–40%) and is outside the European framing used here. This entry does not constitute medical advice.\n", "quality_score": { "d1": 5, "d2": 5, "d3": 5, "d4": 4, "d5": 5, "d6": 5, "d7": 4, "d8": 5, "avg": 4.75, "scored_by": "claude-code-8d", "scored_at": "2026-06-21", "methodology_version": "1.2" }, "reviewer": "8d-eval-2026-06-21", "last_reviewed": "2026-06-21", "reviewed": true, "generated_at": "2026-06-21", "image": { "alt": "A flat vector illustration of a small tick on a leaf beside a single vaccine vial, against a muted forest-toned background." }, "attribution": "Likelier — https://likelier.app", "license": "https://creativecommons.org/licenses/by-sa/4.0/", "support": "https://buymeacoffee.com/kgluszczyk?via=likelier&utm_content=api-fear-single", "canonical_url": "https://likelier.app/tick-borne-encephalitis" }