Introduction
Hepatitis E virus (HEV) infection in Europe is predominantly due to zoonotic genotype 3, transmitted via undercooked pork, game or shellfish (1,2). In the Helsinki and Uusimaa Hospital District (HUS), 70 laboratory-confirmed cases occurred from 2020–2024, with a pronounced peak in early 2024 (3). Seroprevalence in high-income countries ranges from ~6 % to > 50 %, increasing with age and swine exposure (1,2). While most infections are asymptomatic or mild, patients with underlying liver diseases may have more severe outcomes. Diagnosis relies on anti-HEV IgM/IgG serology and PCR detection of viral RNA (4).
Aims & Methods
Objective of this study is to investigate the epidemiology of hepatitis E virus (HEV), its clinical manifestations, and factors associated with hospitalization in the Helsinki University Hospital (HUS) area between 2020 and 2024. We conducted a retrospective registry study including all patients diagnosed with hepatitis E in the HUS area from January 2020 to December 2024. Data were collected from the electronic health record system, the laboratory database, and the shared contact-tracing software of the HUS Epidemiology Unit and Uusimaa welfare regions. Variables analyzed comprised demographic data, symptoms at presentation, key laboratory parameters (ALT, bilirubin, C-reactive protein), probable sources of infection, and details of hospitalization episodes.
Results
Study population: 70 patients (median age 58 years [IQR 45–67]; 58.6 % male).
Clinical manifestations: 92.2 % were symptomatic. The most frequent symptoms were fatigue (55.9 %), abdominal pain (47.5 %), nausea (45.8 %), and jaundice (42.6 %).
Laboratory findings: Median peak ALT was 1 153 U/L (IQR 544–1 538); median peak bilirubin 39 μmol/L (IQR 17–79); median peak CRP 22 mg/L (IQR 11–32).
Genotypes: Of 19 genotyped cases, 3c (21.1 %), 3e (21.1 %), and 3f (57.9 %), with genotype 3f predominant.
Infection sources: Cold-smoked sausages (e.g., mettwurst) were implicated in most domestic cases (69.6 % of identified sources), especially during the early 2024 outbreak. Other identified sources were unspecified meat products (6.5 %), berries (6.5 %), contact with wild animals (e.g., hunting, 4.3 %), blood transfusion (4.3 %), pork meat (4.3%), and game meat (4.3%).
Hospitalization: 50.7 % required ≥1 night of inpatient care. Hospitalized patients were older, had higher ALT, bilirubin, and CRP values, and more comorbidities than outpatients.
Predictors of hospital stay: In a multivariable zero-inflated negative binomial model, higher peak CRP was independently associated with longer hospital stay (β = 0.02; p = 0.005).
Conclusion
The early-2024 surge of HEV cases in the HUS area represents an internationally rare, large genotype 3 outbreak. Cold-smoked meat products were identified as the principal transmission route, although infections linked to blood transfusions, consumption of raw berries, and wildlife contact also occurred. Cases were disproportionately concentrated in men over 50 years of age. Among hospitalized patients, peak CRP emerged as the strongest predictor of inpatient care, and both mortality and incidence of hepatic insufficiency were relatively high given high sanitation standards in Finland. Further multicenter, inter-regional studies are needed to establish statistically robust risk factors for severe outcomes and to guide clinical and public health interventions.
References
1. Luo Q, Chen J, Zhang Y, Xu W, Liu Y, Xie C, ym. Viral hepatitis E: Clinical manifestations, treatment, and prevention. Liver Res. maaliskuuta 2024;8(1):11–21.
2. Hartl J, Otto B, Madden RG, Webb G, Woolson KL, Kriston L, ym. Hepatitis E Seroprevalence in Europe: A Meta-Analysis. Viruses. 6. elokuuta 2016;8(8):211.
3. THL. Terveyden ja hyvinvoinnin laitos. 2024 [referenced: 13. lokakuuta 2024]. Hepatiitti E-tapausten esiintyvyys Suomessa – THL. Available: https://thl.fi/aiheet/infektiotaudit-ja-rokotukset/taudit-ja-torjunta/taudit-ja-taudinaiheuttajat-a-o/hepatiitti-e/hepatiitti-e-tapausten-esiintyvyys-suomessa
4. Dalton HR, Kamar N, Baylis SA, Moradpour D, Wedemeyer H, Negro F. EASL Clinical Practice Guidelines on hepatitis E virus infection. J Hepatol. kesäkuuta 2018;68(6):1256–71.
