Imported malaria remains a clinical and public health challenge in non-endemic countries. This retrospective study analyzed all adult malaria cases diagnosed at Hospitais da Universidade de Coimbra between 2020 and 2024, and the aim was to characterize the epidemiological profile, assess the impact of previous malaria history, and identify biomarkers associated with disease severity. A total of 88 patients were included, mostly male expatriates, with exposure primarily in Angola. Previous malaria history was reported in 52.3% of cases. Severe malaria was diagnosed in 25.0% of patients, being significantly more frequent among those without a prior history of the disease (p = 0.027). These patients had significantly higher creatinine (p = 0.009) and lactate dehydrogenase (p = 0.038) levels, suggesting an increased risk of complications. Urea and parasitemia were independently associated with longer hospital stay (p < 0.001 and p = 0.016, respectively), used here as a proxy for severity. These findings support the hypothesis of semi-immunity in previously exposed individuals and highlight the potential of laboratory biomarkers for clinical risk stratification. Continuous surveillance and targeted prevention strategies for non-immune and semi-immune travelers remain essential, especially in countries like Portugal, where malaria reintroduction can be a real concern.

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