Rift Valley fever (RVF) is a viral disease caused by the RVF virus which is of the “Phlebovirus” type. 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 mild symptoms may include fever, muscle pains, and headaches which often last for up to a week. In humans, the virus can cause several syndromes. Usually, sufferers 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.
In most human cases, the rift valley fever is relatively mild and of short duration, no specific treatment is required for these patients. For the more severe cases, the predominant treatment is general supportive therapy. An inactivated vaccine has been developed for human use. However, this vaccine is not licensed and is not commercially available. It has been used experimentally to protect veterinary and laboratory personnel at high risk of exposure to RVF.
RVF outbreaks occur across the world, with outbreaks occurring elsewhere infrequently. In 1977–78, an estimated 200,000 people were infected and there were at least 594 deaths. As of 8 April 2010, the Ministry of Health had reported 87 human cases infected with Rift Valley fever (RVF), including two deaths. Sporadic cases of RVFV infection in animals have been documented in recent years.