RVF symptoms can be mild and non-specific making a clinical diagnosis difficult, especially early in the course of the disease. Definitive diagnosis of RVF requires laboratory testing of blood or other tissue samples. The virus can be detected in the blood (during illness) and in postmortem tissue by virus isolation in cell culture and by molecular techniques (reverse transcriptase polymerase chain reaction, or RT-PCR).

Antibody testing using enzyme-linked immunoassay (ELISA) can also be used to confirm infection with RVFV by showing the presence of IgM antibodies, which appear briefly as an early response to a recent infection, and IgG antibodies, which persist for several years. Both IgM and IgG antibodies are specific to RVF virus.

US-based clinicians should notify local health authorities immediately of any suspected cases of RVF or other viral hemorrhagic fevers occurring in patients residing in the United States. For laboratory testing requests, contact your local or state health department.