Clinical, Serological, and Molecular Profile of Dengue Patients With Warning Signs During the 2024 Outbreak in Belo Horizonte, Brazil.

Dengue poses a significant arboviral threat in Brazil, with 2024 recording the largest outbreak to date. This prospective observational study was conducted during the 2024 outbreak with unvaccinated patients at Eduardo de Menezes Hospital, Belo Horizonte. A total of 556 patients were included, of whom 169 had complete clinical and laboratory data. Patients with suspected dengue underwent clinical and hematological evaluations, as well as diagnosis by RT-qPCR, and ELISA. These parameters were employed to assess the relationship between diagnostic methods, hematological changes, and disease severity. RT-qPCR confirmed dengue infection in 60% of with clinical symptoms, with partial overlap between PCR positivity and IgM detection, reflecting time-dependent diagnostic windows. High IgG seropositivity indicated widespread prior exposure in the population. Thrombocytopenia was the most consistent hematological finding, with platelet counts declining until day 8 of symptoms and recovering around day 10; a secondary decline was observed in some patients with prolonged hospitalization. No significant differences in clinical severity were observed across serotypes, although DENV-2 showed a trend toward lower platelet counts. These findings highlight the importance of integrating molecular and serological diagnostics during outbreaks and reinforce platelet monitoring as a key parameter for identifying patients at risk of severe dengue.