Last year in October 2007, the Federal Ministry of Health (FMoH), Sudan, requested WHO support to investigate and control a suspected hemorrhagic fever outbreak in White Nile and Sinnar States.
The joint field team arrived in Kosti, White Nile State on 24 October, and investigated reports of human and animal illness in the surrounding area. The team implemented outbreak response activities, including intensified surveillance and case management, social mobilization and outbreak communications. The investigation team reported its findings and recommendations to the FMoH in Khartoum on 28 October, at which point, the FMoH requested additional WHO support for controlling an outbreak of Rift Valley Fever (RVF).
125 cases including 60 deaths were reported from more than 10 localities of White Nile, Sinnar, and Gezeera states. Young adult males are predominantly affected. More than 25 human samples have been found positive for RVF by PCR or ELISA.
Background
Rift Valley Fever (RVF) is a viral infection that primarily affects animals but also has the capacity to infect humans. Infection can cause severe disease in both animals and humans, leading to high rates of disease and death. The disease also results in significant economic losses due to death and abortion among RVF-infected livestock.
The virus was first identified in 1931 during an investigation into an epidemic among sheep on a farm in the Rift Valley of Kenya. Since then, outbreaks have been reported in sub-Saharan and North Africa. In 1997-98, a major outbreak occurred in Kenya, Somalia and Tanzania and in September 2000, RVF cases were confirmed in Saudi Arabia and Yemen, marking the first reported occurrence of the disease outside the African continent and raising concerns that it could extend to other parts of Asia and Europe.
Transmission to humans
The vast majority of human infections result from direct or indirect contact with the blood or organs of infected animals. The virus can be transmitted to humans through the handling of animal tissue during slaughtering or butchering, assisting with animal births, conducting veterinary procedures, or from the disposal of carcasses or fetuses. Certain occupational groups such as herders, farmers, slaughterhouse workers and veterinarians are therefore at higher risk of infection. The virus infects humans through inoculation, for example via a wound from an infected knife or through contact with broken skin, or through inhalation of aerosols produced during the slaughter of infected animals. The aerosol mode of transmission has also led to infection in laboratory workers.
There is some evidence that humans may also become infected with RVF by ingesting the unpasteurized or uncooked milk of infected animals.
Human infections have also resulted from the bites of infected mosquitoes, most commonly the Aedes mosquito.
