FIG 2.

Pathways to diagnose probable and confirmed arbovirus infection. For patients with suspected active viral replication, the direct detection of pathogen nucleic acid in serum or affected tissue or growth of virus in culture confirms diagnosis. Most patients present after the period of viremia, thereby requiring the use of serologies. A positive IgM ELISA from serum or CSF establishes a probable diagnosis. Confirmation of disease requires detection of serum-neutralizing antibodies, seroconversion, or a 4-fold increase in either IgM or IgG titers from paired sera. Neuroinvasive disease can be confirmed by the same methods or by negative CSF IgM ELISA testing against other endemic arboviruses that circulate in the same geographic area.