phleboviruses

Phleboviruses are a genus of viruses in the family Phenuiviridae, order Bunyavirales. They are enveloped, spherical viruses with a tripartite, negative-sense RNA genome organized into L, M, and S segments. The L segment encodes the RNA-dependent RNA polymerase, the M segment encodes the glycoproteins Gn and Gc, and the S segment encodes the nucleocapsid protein and a nonstructural protein. This genome organization is characteristic of many bunyaviruses.

Transmission and ecology: Phleboviruses are primarily arthropod-borne (arboviruses). They are transmitted mainly by sandflies and mosquitoes, with some species increasingly recognized in diverse geographic settings. The viruses often circulate in animal reservoirs, and humans are incidental hosts. Transmission dynamics are influenced by vector ecology, climate, and rainfall, which affect vector populations and virus amplification in endemic areas.

Clinical features and notable viruses: The clinical spectrum ranges from mild, self-limited febrile illness to more severe disease such as meningitis, encephalitis, or hemorrhagic fever, depending on the virus and host factors. Notable phleboviruses include Rift Valley fever virus (RVFV), associated with outbreaks in Africa and the Arabian Peninsula and affecting both livestock and humans, and Toscana virus (TOSV), a common cause of viral meningitis in parts of Southern Europe. Other sandfly-borne viruses, such as Sandfly fever Naples virus and Sandfly fever Sicilian virus, also cause febrile illness.

Diagnosis and prevention: Diagnosis is by PCR, virus isolation, or serology. There is no widely available specific antiviral treatment or universal human vaccine for phleboviruses; management is supportive. Prevention focuses on vector control and reducing exposure to vectors, with vaccination of livestock used to reduce RVFV transmission in endemic settings.