Press Release WHO/2 6 January 1998   KENYA: RIFT VALLEY FEVER VIRUS DETECTED IN DISEASE OUTBREAK   Rift Valley fever (RVF) virus has so far been confirmed by virus isolation in cultures of samples from three cases of the hitherto mysterious disease outbreak in north-eastern Kenya, a World Health Organization (WHO) Collaborating Centre has reported. Although Rift Valley fever virus has been detected by the WHO Collaborating Centre at the National Institute of Virology (NIV) in South Africa in specimens taken from more than one victim, RVF may not be the only cause of the 300 deaths observed in the current disease outbreak as some other cases have shown no evidence of RVF infection. Because the population affected is undernourished and subject to various diseases, particularly those associated with a lack of clean drinking water and of health services, other severe diseases that normally occur in the area, such as shigellosis and malaria, may partially explain the large number of deaths in the region. Additional epidemiological studies using a uniform case definition are needed to better understand the scope and nature of the epidemic as well as the support and control measures required. Laboratory investigations, including on samples taken from animals, are continuing at NIV and another WHO Collaborating Centre, at the Centers for Disease Control and Prevention (CDC) in Atlanta, USA. Rift Valley fever virus is a member of the family Bunyaviridae and is in the Phlebovirus genus. The virus was first isolated in 1931 during a disease outbreak in livestock on a farm located in the Rift Valley of Kenya. The virus is endemic to Africa, south of the Sahara desert, but infections have periodically extended into Egypt. During epizootics (epidemics in animals), the virus causes spontaneous abortion in ewes and cows and deaths in lambs and calves. In humans, the virus produces a usually non-fatal dengue-like illness. Less frequently, infection results in retinitis, encephalitis and haemorrhagic disease, the latter condition being consistent with the present outbreak. Rift Valley fever virus is transmitted by mosquitoes and many different species can serve as vectors. Humans can also be infected by contact with blood or body fluids from infected animals which may occur during slaughtering of the animals or handling of aborted foetuses. The risk of human-to-human infection through direct contact appears to be very low. WHO does not recommend any restrictions on travel to Kenya as the area affected is remote and far from the tourist centres of Nairobi, Mombasa and the game parks. Related story: Disease Outbreak in Kenya: HO Does Not Recommend Travel Restrictions 30 December, 1997) For further information, please contact Gregory Hartl, Health Communications and public Relations , WHO, Geneva. Telephone (+41 22) 791 4458. Fax (+41 22) 791 4859. Email hartlg@who.ch All WHO Press Releases, Fact Sheets and features as well as other information on this subject can be obtained on the Internet on the WHO home page at http://www.who.ch/ .