The emergence of autochthonous dengue fever in Iran: a comprehensive analysis of the first major outbreak in Sistan and Baluchestan Province, 2024

Dengue fever (DF) is an emerging disease in Iran. The first large-scale local transmission outbreak occurred in southeastern Iran in 2024. This study aimed to investigate the demographic, geographical, and clinical features of this outbreak in Sistan and Baluchestan Province. This retrospective cross-sectional study investigated a recent DF outbreak in Chabahar County, Sistan and Baluchestan Province, southeastern Iran. Data from the centers for disease control (CDC) of Iran’s Ministry of Health including socio-demographic factors, travel history to endemic areas, laboratory results, clinical symptoms, hospitalization records, disease severity, and treatment outcomes were analyzed. Statistical analysis was performed using SPSS software. A total of 871 DF cases were recorded in Sistan and Baluchestan Province in 2024, with the highest burden (98%) reported from Chabahar County. The incidence rate peaked during the last week of October, indicating a seasonal pattern. Patients were predominantly male (59.9%), with a mean age of 33.7 years (SD: 15.4). The most frequent clinical symptoms were fever, headache, and muscle or joint pain, reported in more than 97% of patients. Rapid diagnostic tests (RDT) with Non-Structural Protein 1 (NS1) antigen were used for primary confirmation in 83.3% of cases. Importantly, 4.8% of DF patients were diagnosed with dengue hemorrhagic fever (DHF). Common hematological abnormalities included low hematocrit levels (61.9%), thrombocytopenia (42.6%), and leukopenia (43.5%). Molecular testing identified circulation of DENV-1 and DENV-2 serotypes. Only 8.3% of total patients required hospitalization; all patients recovered fully, and no fatalities related to DF were reported. This study documents the first large-scale local transmission outbreak of DF in Iran. It provides important information on geographical, demographic, and clinical features of DF in the study areas, which may serve as an effective guide for health systems to control this emerging disease. Importantly, the establishment of Aedes aegypti in southern Iran marks a critical transition toward endemicity, underscoring the need for sustained vector surveillance and control measures.es