Encephalitis, a severe neurological disease with a high mortality rate, can result in lifelong complications. Common agents often caused by an infection include herpesviruses, enteroviruses, and arboviruses. However, the causative agent remains unidentified in over 50% of encephalitis cases, complicating treatment and patient recovery. Since 2013, there has been a noticeable increase in encephalitis cases in northeastern Brazil, with a fourfold rise compared to previous years. With its climate and urban conditions conducive to the spread of arboviruses, this region has witnessed the co-circulation of the Zika, chikungunya, and dengue viruses since 2014. In addition, several other arboviruses associated with encephalitis exist, many of which are still unknown or rarely observed in Brazil. However, few studies have investigated this subject in the country. In this project, we aim to examine the viruses linked to encephalitis cases in northeastern Brazil and determine whether the observed increase is due to a new virus circulating in the region or the already endemic arboviruses.