Bunyaviridae Overview

1. Bunyaviruses are prevalent throughout the United States, including Sin Nombre Virus in the Southwest and California Encephalitis Virus.
2. Bunyaviruses are almost all transmitted by arthropods. Hantaviruses are transmitted in rodent urine, but are the exception to the rule despite their infamy.
3. Hantavirus epidemics in the United States have been associated with El Nino rainfall that provide good conditions for Sigmodon rodent vector proliferation.
4. Bunyaviridae have mostly negative sense RNA. Phleboviruses are the exception, with only 1 segment of three that is ambisense.
5. The 3 segments of Bunyaviridae are identified as L(large), M(medium), and S(short). S contains the Capsid protein and a nonstructural protein, M contains the two envelope proteins, and L contains the RNA dependent RNA polymerase.
6. Each segment has its own helical nucleocapsid. At least one of each L, M and S must be present in a mature virion to be infectious, but there can be more than one of each.
7. Bunyaviridae exhibit cap-stealing, the use oligonucleotide caps stolen from host mRNA as primers in transcription.
8. Bunyaviridae are associated with numerous clinical presentations, including encephalitis, Hantavirus Pulmonary Syndrome (HPS), and Hemorrhagic Fever with Renal Syndrome (HFRS).
9. The diseases HPS and HFRS are due to the host cytokine immune response, not viral induction of cell death.
10. Prevention strategies are essential as there are no human vaccines, and include reduction of exposure to arthropod vectors through DEET or netting. Other important strategies include immunizing African livestock and wearing protective masks when cleaning out rodent infested areas.