WHO Collaborating Centre Network
Many of the internationally important outbreaks involve the diverse group of arboviral diseases and viral haemorrhagic fevers. The WHO Collaborating Centres global network of centres for these diseases has collaborating centres in every WHO region and about one third of the centres are in developing countries. These centres work in close partnership with WHO and Member States to investigate, confirm and control outbreaks. Through the WHO Collaborating Centre searchable database, information about those centres and laboratories dealing with specifically with Rift Valley fever is available.
Remote sensing to help predict Rift Valley fever outbreaks
WHO has been working with remote sensing data provided by the National Space Agency of the United States to investigate environmental conditions, including vegetation and rainfall, which can help to provide early warning of possible outbreaks of Rift Valley fever in Africa.
Environmental impact and the East African outbreak, 1997-1998
Outbreaks of Rift Valley fever are associated with an increase in the mosquito vector population following increased water availability after heavy rains and floods, or due to man-made dams or irrigation systems and open water storage construction.
In December 1997 an outbreak of unidentified disease with a high number of deaths was reported from Kenya and Somalia, associated with heavy rains which had been occurring since October 1997. Initial investigations by a WHO national team found deaths occurring in humans and high rates of spontaneous abortions and deaths from haemorrhage among domestic food animals. Rift Valley fever virus was confirmed by the WHO Collaborating Centres in South Africa and the United States, part of the WHO Global Collaborating Centres Network for haemorrhagic fevers and arboviruses. A full-scale investigation and containment measures were carried out in 1998 by WHO and its partners. More details are available in An outbreak of Rift Valley Fever, Eastern Africa, 1997-1998.
Saudi Arabia and Yemen: First cases of Rift Valley fever reported outside Africa, 2000
The emergence of Rift Valley fever in Yemen and in the Kingdom of Saudi Arabia (KSA) in September 2000, led to 1 328 human cases including 166 human deaths and 20 000 abortions in livestock in Yemen and 882 human cases including 124 deaths in the KSA. The outbreak was located in the area of Wadi Mawr, on a coastal plain that extends from the southern tip of Yemen into the Jizan area of Saudi Arabia. The Ministry of Health of Saudi Arabia described a simultaneous outbreak of Rift Valley fever in the Jizan area. Both countries organized national efforts to limit the spread of disease, provide treatment to those affected and track the course of the outbreak. WHO provided support with experts in virology, epidemiology, laboratory diagnostics and entomology.
To control the outbreak, the governments carried out intensive vector-control measures, restricted animal movements, ran education campaigns to prevent exposure to infected animals and upgraded local hospitals to provide treatment to patients. Saudi Arabia and Yemen worked together to share information, including investigation protocols and coordinated logistics across the border.
The results of the investigation can be found in: Outbreak of Rift Valley fever, Yemen, August-October 2000