rift valley fever rift valley fever rift valley fever (rvf) is a viral disease of humans and livestock that can cause mild to severe symptoms. the mild symptoms may include: fever, muscle pains, and headaches which often last for up to a week. the severe symptoms may include: loss of sight beginning three weeks after the infection, infections of the brain causing severe headaches and confusion, and bleeding together with liver problems which may occur within the first few days. those who have bleeding have a chance of death as high as 50%. rift valley fevertem micrograph of tissue infected with rift valley fever virusspecialtyinfectious diseases, veterinary medicine symptomsfever, muscle pains, headachescomplicationsloss of sight, confusion, bleeding, liver problemsdurationup to a weekcausesphlebovirus spread by an infected animal or mosquitodiagnostic methodfinding antibodies or the virus in the bloodpreventionvaccinating animals against the disease, decreasing mosquito bitestreatmentsupportive carefrequencyoutbreaks in africa and arabia the disease is caused by the rvf virus. it is spread by either touching infected animal blood, breathing in the air around an infected animal being butchered, drinking raw milk from an infected animal, or the bite of infected mosquitoes. animals such as cows, sheep, goats, and camels may be affected. in these animals it is spread mostly by mosquitoes. it does not appear that one person can infect another person. the disease is diagnosed by finding antibodies against the virus or the virus itself in the blood. prevention of the disease in humans is accomplished by vaccinating animals against the disease. this must be done before an outbreak occurs because if it is done during an outbreak it may worsen the situation. stopping the movement of animals during an outbreak may also be useful, as may decreasing mosquito numbers and avoiding their bites. there is a human vaccine; however, as of 2010 it is not widely available. there is no specific treatment and medical efforts are supportive. outbreaks of the disease have only occurred in africa and arabia. outbreaks usually occur during periods of increased rain which increase the number of mosquitoes. the disease was first reported among livestock in rift valley of kenya in the early 1900s, and the virus was first isolated in 1931. signs and symptoms in humans, the virus can cause several syndromes. usually, they have either no symptoms or only a mild illness with fever, headache, muscle pains, and liver abnormalities. in a small percentage of cases (< 2%), the illness can progress to hemorrhagic fever syndrome, meningoencephalitis (inflammation of the brain and tissues lining the brain), or affect the eye. patients who become ill usually experience fever, generalised weakness, back pain, dizziness, and weight loss at the onset of the illness. typically, people recover within two to seven days after onset. about 1% of people with the disease die of it. in livestock, the fatality level is significantly higher. pregnant livestock infected with rvf abort virtually 100% of foetuses. an epizootic (animal disease epidemic) of rvf is usually first indicated by a wave of unexplained abortions. other signs in livestock include vomiting and diarrhoea, respiratory disease, fever, lethargy, anorexia and sudden death in young animals. cause virology rift valley fever phlebovirus phlebovirus virion and genome virus classification (unranked): virus realm: riboviria kingdom: orthornavirae phylum: negarnaviricota class: ellioviricetes order: bunyavirales family: phenuiviridae genus: phlebovirus species: rift valley fever phlebovirus the virus belongs to the bunyavirales order. this is an order of enveloped negative single stranded rna viruses. all bunyaviruses have an outer lipid envelope with two glycoproteins—g(n) and g(c)—required for cell entry. they deliver their genome into the host-cell cytoplasm by fusing their envelope with an endosomal membrane. the virus' g(c) protein has a class ii membrane fusion protein architecture similar to that found in flaviviruses and alphaviruses. this structural similarity suggests that there may be a common origin for these viral families. the virus' 11.5 kb tripartite genome is composed of single-stranded rna. as a phlebovirus, it has an ambisense genome. its l and m segments are negative-sense, but its s segment is ambisense. these three genome segments code for six major proteins: l protein (viral polymerase), the two glycoproteins g(n) and g(c), the nucleocapsid n protein, and the nonstructural nss and nsm proteins. transmission