NEAS prospective case-control study aims to define the association between the exposure to arbovirus (Zika, Dengue and Chikungunya) and the development of a neurological syndrome in patients from Colombia, a country with endemic transmission of arbovirus. The cases are defined as individuals that present with new onset of a neurological syndrome of unknown etiology, including but not limited to encephalitis, myelitis, meningitis, polyneuropathy/Guillain-Barre syndrome and cranial nerve involvement. There are two age-matched control groups: 1) household controls and 2) controls with a febrile syndrome of unknown etiology that do not present neurological involvement. The estimated sample size in the study is 50 participants in each group (cases and controls 1 and 2). The time to collect the complete sample size is between 12-24 months, and depends on the local incidence of cases.