Though not well known in the United States, Rift Valley fever (RVF) is a dangerous viral disease that is a major cause for concern in Africa. RVF primarily affects animals and can infect several species, including cattle, sheep, goats and camels. Protecting animals from the virus is extremely important in farming, as it has a high death rate for some animals of a particular age (up to 90% for lambs) and can cause a near-100% abortion rate among pregnant ewes. These losses can be devastating for those who raise livestock.
Rift Valley fever is also a concern, however, because it can sometimes infect humans. This typically occurs through contact with infected animals, but the virus can also be spread by the bite of infected mosquitoes or blood-feeding flies. Some evidence suggests that humans can even be infected by drinking unpasteurized or uncooked milk from infected animals.
Typically a human infection with RVF is mild and passes without treatment, but there are three more serious forms of the disease: one that leads to retinal lesions (and possible blindness); one that leads to meningoencephalitis and leaves the victim vulnerable to residual neurological problems; and one that leads to haemorrhagic fever, with a death rate as high as 50%. Prior to 1997 the disease had been limited to Sub-Saharan regions, but outbreaks have since occurred in Saudi Arabia, Mauritania, Egypt and Yemen, and outbreaks in Kenya, Somalia and Tanzania from 2006-2007 led to human deaths, raising concern that the virus could continue to spread. The United States federal government has also classified RVF as a potential biowarfare threat. More