Abstract

Background:
Sandfly fever viruses (Phleboviruses, family Phenuiviridae) are important but neglected causes of febrile illness in Africa, the Mediterranean Basin, the Middle East, and Central Asia. Their clinical presentation overlaps with malaria and enteric fever, complicating diagnosis. In Sudan, historical studies documented outbreaks in Northern and Khartoum provinces, but targeted seroprevalence data remain limited, and no recent surveys have
addressed their broader distribution.

Aim:
This study aimed to uncover hidden viral etiologies and provide evidence for the endemic circulation of these pathogens

Methods:
We conducted a cross-sectional serological study of 201 febrile, Malaria-Negative patients from Northern, Khartoum, El-Gadarif, and Red Sea states. Serum samples were tested for immunoglobulin G (IgG) and immunoglobulin M (IgM) antibodies against Sandfly Fever Sicilian Virus (SFSV), Sandfly Fever Naples Virus (SFNV), Toscana Virus (TOSV), and Cyprus Virus (CYPV) using a highly specific Indirect Flouresence AntibodyTechnique for detection of IgM and IgG. Statistical analysis assessed prevalence differences between states.

Results:
IgG antibodies against all four viruses were detected in all states, confirming widespread exposure. Overall IgG prevalence was highest for SFSV (46.7%) and CYPV (45.3%), followed by SFNV (29.9%) and TOSV (29.4%). Significant differences between states were observed for SFSV, SFNV, and CYPV (p < 0.05). IgM antibodies, reflecting recent infection, were less frequent, with overall prevalence ranging from 2.5% (SFNV) to 12.7% (SFSV). SFNV IgM was absent in Northern state but present in the other three states. Notably, antibodies against CYPV and TOSV were detected for the first time in Sudan, expanding the known spectrum of circulating phleboviruses.

Conclusion:
This study provides new evidence of the endemic circulation of four sandfly fever viruses in Sudan, including the first reports of CYPV and TOSV. High IgG prevalence underscores widespread past exposure, while IgM detection indicates ongoing transmission. These findings highlight the need to consider phleboviruses in the differential diagnosis of febrile illnesses in Malaria-Negative patients and emphasize the importance of further epidemiological, molecular, and virological investigations to assess their distribution, burden, and public health impact.

Key words: Febrile patients; IFA; Sandfly phleboviruses; Seroprevalence; Sudan.