Toscana virus (TOSV) is a sand fly-borne phlebovirus in the family Phenuiviridae that causes febrile illness and sometimes neuroinvasive disease in humans.
Biology and Epidemiology
Toscana virus is a member of the genus Phlebovirus within the family Phenuiviridae. It has a tri-segmented negative-sense RNA genome encoding structural and non‑structural proteins. The virus was first isolated from Phlebotomus sand flies in Tuscany, Italy, in 1971, and is now recognised across southern Europe, northern Africa and the wider Mediterranean basin. Transmission to humans occurs through the bite of infected female sand flies, principally Phlebotomus perniciosus and Phlebotomus perfiliewi, which are most active during summer and early autumn. Experimental studies suggest that the virus is maintained in sand fly populations through vertical and venereal transmission. Although antibodies have been detected in dogs and livestock, definitive vertebrate reservoirs remain uncertain. Human infection is seasonal and peaks when sand fly populations peak. Clinically, Toscana virus infection ranges from mild, self‑limited febrile illness to neuroinvasive disease presenting as aseptic meningitis or encephalitis. It is the only sand fly‑borne phlebovirus known to cause central nervous system disease. Most cases occur in Mediterranean countries such as Italy, Spain, France, Greece and Portugal, but imported cases have been reported in northern Europe among travellers returning from endemic areas. Seroprevalence studies indicate that exposure is common in endemic regions, with neutralising antibodies detected in more than 20 % of residents in some areas. There is no specific antiviral therapy or vaccine; management is supportive, and prevention relies on reducing sand fly bites through protective clothing, insect repellents and vector control.
Key Cases and Public Health Notes
Since its identification, Toscana virus has been associated with clusters of meningitis and encephalitis during summer months. In Italy, particularly in the regions of Emilia–Romagna and Umbria, the virus accounts for a notable proportion of central nervous system infections. Reports from southern France and Spain describe patients presenting with aseptic meningitis and influenza‑like illness who tested positive for TOSV. Imported cases have been documented in Sweden, the United Kingdom and Germany among travellers returning from the Mediterranean. Serological surveys show high seropositivity in populations in Cyprus, Greece and parts of Italy. Evidence of antibodies in dogs, livestock and birds suggests these animals are bitten frequently, but their role as reservoirs remains unclear. Phylogenetically, TOSV is closely related to other sand fly fever viruses such as the Naples and Sicilian viruses, yet only Toscana virus has confirmed neurovirulence. Toscana virus is an important arthropod‑borne pathogen of the Mediterranean region. It is distinguished among sand fly fever viruses by its ability to cause meningitis and encephalitis, although most infections are mild. The absence of a vaccine or specific therapy means that personal protective measures and vector surveillance are central to prevention efforts. Related Terms: Sandfly fever Naples virus, Sandfly fever Sicilian virus, Phleboviruses, Rift Valley fever virus, Arboviral encephalitis