Oropouche fever is an arboviral disease caused by the Oropouche virus (OROV), an Orthobunyavirus transmitted by arthropods, with Culicoides paraensis as the main urban vector. The emergence of a new genotype due to viral reassortment led to disease expansion beyond the Amazon region starting in 2023. The first deaths were reported in 2024, along with evidence of congenital infection. There is no specific treatment, and prevention relies on personal protective measures. A previously healthy 6-year-old girl from Japeri (Rio de Janeiro, RJ) was transferred to a tertiary public hospital in Rio de Janeiro in May 2025 for investigation of thrombocytopenia. Five days before admission, she developed abdominal pain, headache, reduced appetite, bruising, and gum bleeding. She denied fever or other symptoms. On admission, thrombocytopenia was confirmed, and dengue was initially suspected but ruled out by negative serology and antigen testing. A peripheral blood smear confirmed thrombocytopenia (20,000 to 50,000 platelets) and also showed macroplatelets, mild lymphocytic atypia, and microcytosis. Based on these findings, she was diagnosed with immune thrombocytopenic purpura (ITP), and prednisolone was prescribed for seven days. After treatment, she showed laboratory improvement without further bleeding and was discharged. On the 6th day after discharge, she developed a 39°C fever and severe headache, prompting readmission. A blood count showed an abrupt platelet drop after an earlier upward trend. At that time, tests for other arboviruses endemic to Brazil were collected. Oropouche fever was confirmed by molecular detection of OROV in blood/serum and urine. A new peripheral smear was performed with no changes compared to the initial study. The patient improved clinically and laboratorily and was discharged after ten days. She is currently being followed as an outpatient. The patient continues to have detectable viral load in urine up to the 12th week of illness and remains under follow-up. Given the disease’s expansion and the emergence of severe Oropouche cases, this report illustrates the urgent need to include OROV in the syndromic investigation of ITP and arboviral diseases in Brazil.
Almeida et al. (2026) studied this question.