欧洲疾控中心-快速风险评估_欧盟_欧洲经济区多国爆发甲型肝炎（英）-2025.6_9页_202kb

Multi-country Outbreak of Hepatitis A in the EU/EEA (RAPID RISK ASSESSMENT)

Core Content

This document outlines a multi-country outbreak of hepatitis A virus (HAV) subgenotype IB in the European Union/European Economic Area (EU/EEA) between January and May 2025. The outbreak primarily affects specific high-risk groups, including adults experiencing homelessness, individuals who use or inject drugs, and members of the Roma communities. The document also includes microbiological data, risk assessments, and recommendations for public health authorities.

Main Points

Epidemiological Situation

• Countries Affected: Austria, Czechia, Hungary, and Slovakia have reported a higher-than-expected number of HAV subgenotype IB cases.
• Outbreak Trends:
  • Austria: 87 confirmed cases, with 44 under investigation. 63% required hospitalisation, and 3 deaths were reported.
  • Czechia: 600 confirmed cases, with 18% from the Roma population. 86% of cases were hospitalised, and 6 deaths were reported.
  • Hungary: 641 suspected cases, 530 confirmed. 13 cases involved people experiencing homelessness.
  • Slovakia: A significant increase since 2022, with 880 cases in 2025 and no deaths. 47% of cases were from Roma communities.
  • Germany: Three non-fatal cases with no known epidemiological link, no ongoing outbreak reported.

Microbiological Findings

• Strain Identification: Two HAV subgenotype IB clusters were identified: Cluster a (Hungary) and Cluster b (Slovakia).
• Sequence Data:
  • Cluster a: Reference strain 3256048_HUN_2025, with 12 cases in Austria, 57 in Hungary, and 3 in Germany.
  • Cluster b: Reference strain ERS23282329, with 31 cases in Austria and 13 in Slovakia.
• Genetic Variability: The two clusters differ by a single nucleotide in the VP1/P2A junction, a highly variable region of the HAV genome.

Risk Assessment

• High-Risk Groups:
  • People experiencing homelessness.
  • Individuals who use or inject drugs.
  • Roma communities.
  • People with chronic liver disease or immunosuppression.
• Risk Factors:
  • Poor sanitary conditions.
  • Close contact with infected individuals.
  • Substance use.
  • Age (risk increases with age).
  • Travel to high-endemicity areas.

Recommendations

• Surveillance and Case Detection:

  • Investigate transmission routes (e.g., foodborne or spill-over into other high-risk groups).
  • Sequence a representative subset of cases, including those from different regions and population groups.
  • Use the HAVnet protocol to sequence the 460 bp region of the VP1/P2A junction.
  • Share epidemiological and microbiological data with ECDC via EpiPulse Events.

• Vaccination Strategies:

  • Implement targeted single-dose pre-exposure vaccination for high-risk groups (e.g., Roma, homeless, drug users).
  • Administer post-exposure prophylaxis (hepatitis A vaccine or immunoglobulins) to close contacts, following national guidelines.
  • Consider targeted vaccination in low and very low endemicity settings for high-risk populations.

• Outreach and Awareness:

  • Tailor outreach efforts to meet the needs, attitudes, and knowledge of high-risk groups.
  • Adapt information for different languages and literacy levels.
  • Address misinformation and stigma.
  • Embed vaccination and hygiene interventions into accessible services (e.g., shelters, food banks, drug treatment centers).
  • Use ECDC's survey tool to assess attitudes and knowledge around HAV and vaccination.

• Hygiene and Access:

  • Ensure availability of water and soap in public and accessible areas.
  • Improve access to healthcare for vulnerable populations.
  • Address upstream determinants such as homelessness and substance use.

Key Information

• The outbreak is primarily affecting adults in high-risk groups.
• Subgenotype IB is the predominant strain in the outbreak.
• Sequencing plays a critical role in identifying transmission clusters.
• Vaccination is recommended for both pre- and post-exposure.
• Outreach and information adaptation are essential to improve vaccination uptake and disease prevention.
• Germany is considered a non-affected country, with no ongoing outbreak reported.

Limitations

• Under-ascertainment of HAV infections due to asymptomatic or mild cases.
• Limited outbreak investigation and contact tracing in some high-risk populations.
• Not all HAV samples are sequenced, so the extent of the outbreak may not be fully understood.
• Other HAV clusters and outbreaks are under investigation, but not included in this assessment due to different strains.