**2.3 Saint Louis encephalitis virus (SLEV)**

Saint Louis encephalitis virus (SLEV) is a flavivirus, a member of the Japanese encephalitis virus serogroup, initially identified in 1933 in Saint Louis, Missouri, USA, as encephalitis lethargica [64], during an outbreak involving 475 cases with 71 deaths (14.9%) [65]. The encephalitis lethargica occurred in Saint Louis in 1919, 1924, and 1932 [65]. Studies on SLEV in Latin America also lack, regardless of its epidemiological situation [66]. In a bibliometric study performed in December 2016 [64], only 955 articles were recovered from PubMed (44% from the United States of America, 4% from Brazil, and 4% from Argentina) [64]. After 6 years of that bibliometric assessment of SLEV, only 172 additional articles have been published, clearly showing the lack of research on this flavivirus.

*Culex* species generally transmit SLEV as vectors and birds as animal hosts. Most SLEV infections are asymptomatic, but clinical manifestations range from nonspecific febrile syndrome to febrile headache, aseptic meningitis, and encephalitis, with fatality ranging from 3 to 30% [67]. In the case of Latin America, SLEV is one of the flaviviruses that circulate in Brazil [68]. Reports from Argentina [69, 70], Colombia [71], Cuba [72], Ecuador [73], French Guiana [74], Guatemala [75], Mexico [76], Panama [67, 77], Peru [78], and Uruguay [79] have also been published, among other possible identifications in other Latin countries. The primary SLEV mosquito vectors in some endemic areas include *Culex tarsalis*, *C. pipiens*, and *C. quinquefasciatus* [80, 81]. Like most arboviruses that cause central nervous system (CNS) disease in humans, most SLEV infections are asymptomatic or mild, with symptom onset 5–15 days after exposure and exhibiting a broad range of clinical presentations [80].
