Sindbis virus is widely and continuously found in insects, such as Culex mosquitoes, in Eurasia, Africa, and Oceania. However, clinical infection in humans has almost exclusively been reported in northern Europe where it is endemic and where large outbreaks occur intermittently.
Arenaviruses cause diseases with two types of clinical presentations: neurological and haemorrhagic fever. However, asymptomatic arenavirus infection may occur.