Saint Louis encephalitis virus and other arboviruses in the differential diagnosis for dengue.

Brazil is a tropical country with a wide variety of flora and fauna that includes many arthropods, especially mosquitoes and midges. This ecological diversity facilitates the maintenance of arboviral cycles and the emergence of novel arboviral pathogens. Indeed, many outbreaks attributable to zoonotic arboviruses such as Oropouche, Mayaro, Rocio virus (ROCV), Saint Louis encephalitis virus (SLEV) and yellow fever virus have been seen in the recent past. Furthermore, due to the increase in international travel, arboviruses present in other American countries, such as the emergent viruses West Nile and Chikungunya, have already been introduced, or could be introduced to this region in the future. The southeastern, northeastern, and southern regions of Brazil, which house the majority of the population (200 million inhabitants), are infested by the Aedes aegypti, Aedes albopictus, and Culex mosquitoes. Aedes aegypti, the vector for the dengue virus, is responsible for large epidemics with high morbidity and mortality. Cases of meningoencephalitis in Brazil have also been attributed to the dengue virus, and control of virus spread is a high priority topic for public health authorities; in addition to controlling the Aedes aegypti population, dengue control strategies also involve clinical and serological diagnosis of infection. However, testing only focuses on dengue, and other arboviruses that produce acute febrile illness and meningoencephalitis can remain undetected. A recent study in Revista da Sociedade Brasileira de Medicina Tropical/Journal of the Brazilian Society of Tropical Medicine showed that horses can be infected by SLEV and ROCV1. These are ribonucleic acid (RNA) viruses belonging to the Japanese encephalitis serocomplex in the Flavivirus genus of the Flaviviridae family. This serocomplex includes mostly the arboviruses that cause meningoencephalitis and have birds as reservoirs and mosquitoes of the Culicinae subfamily as vectors. SLEV is responsible for an increasing number of cases in Brazil, particularly in the State of São Paulo. In 2004, SLEV was isolated from a patient diagnosed with dengue fever in the City of São Pedro2. In 2006, eight patients with acute febrile illness from the City of Ribeirão Preto were found to be