Rift Valley Fever virus protein and RNA. Molecular model of a nucleocapsid protein from the Rift Valley Fever virus (RVF), bound with single-stranded RNA (ribonucleic acid). Capsid proteins form a protective coat around the nucleic acid core of the virus. This protein is a circular hexamer (6-fold structure). This virus is an example of viral zoonosis, the transmission of disease between animals and humans. In humans the disease results in fever and patients usually recover within a few days. A complex between RNA and a protein is known as a ribonucleoprotein.