This target organthe liver in Rift Valley fever, the brain in La Crosse encephalitis, the liver and vascular endothelium in Crimean-Congo hemorrhagic fever and hemorrhagic fever with renal syndrome, and the lung in hantavirus pulmonary syndromeis damaged, and a specific disease occurs. The damage to the kidneys in hemorrhagic fever with renal syndrome and to the brain and retina in Rift Valley fever occurs after humoral antibody is formed. These complications have been postulated to result from a host reaction. The initial response to bunyavirus infection is the production of interferon. Bunyaviruses are sensitive to the action of interferon, so this response may play a protective role.
Humoral antibody is also protective.
The appearance of antibody, either natural or passively administered, is associated with the disappearance of virus from the blood. The role of cell-mediated immunity has not been fully evaluated. Bunyaviruses are found throughout the world, but each serotype has a limited geographic distribution because it relies on one or, at best, a few arthropod species to maintain its natural cycle. Hantaviruses are maintained in rodent reservoirs and are not arthropod borne. Hantaviruses are maintained in a rodent reservoir.