Distinct Clinical and Laboratory Features of Measles in Adults and Children During the 2024 Epidemic: A Retrospective Study from a Romanian Tertiary Infectious Diseases Center.

Background and Objectives: Romania reported the highest measles incidence in the European Union during the 2023-2024 epidemic, largely driven by declining vaccination coverage. We aimed to characterize the epidemiological, clinical, and laboratory profile of hospitalized measles patients and to identify age-related differences, with particular emphasis on systemic and hepatic involvement. Materials and Methods: We conducted a retrospective observational study including 360 consecutive patients with laboratory-confirmed measles admitted to a tertiary infectious disease hospital in northeastern Romania between 1 January and 31 December 2024. Demographic, clinical, laboratory, therapeutic, and outcome data were collected. Pediatric (<15 years) and adult patients were compared using appropriate statistical tests. Results: Children accounted for 71.4% of cases, including 16.1% infants under one year. Over 90% of patients were unvaccinated or incompletely vaccinated. Household transmission represented the most frequent identifiable source. Adults presented significantly higher inflammatory markers and more pronounced hepatic involvement than children. ALT elevation occurred in 63.1% of adults versus 34.2% of children (p < 0.001), with moderate-to-severe cytolysis predominantly observed in adults (34.9% vs. 1.9%, p < 0.001). Pulmonary complications were documented in 28% of cases, mainly viral interstitial pneumonia. Thrombocytopenia was significantly more frequent in adults (p < 0.001). Overall mortality was 0.27%, occurring in an unvaccinated infant with secondary bacterial pneumonia. Conclusions: The 2024 measles epidemic in our area was characterized by sustained transmission among unvaccinated individuals and frequent systemic involvement. Hepatic dysfunction emerged as a prominent feature in adults, suggesting a shifting clinical phenotype in contemporary outbreaks. Strengthening vaccination coverage and early recognition of systemic complications remain critical to reducing measles-related morbidity and mortality.