Yellow fever in Kenya: the need for a country-wide surveillance programme.

Since the emergence of yellow fever (YF) as a public health threat in Kenya in 1992-1993, low level transmission of the virus to humans has continued to occur. A programme of YF surveillance has been instrumental in the monitoring of YF activity and has clearly demonstrated an expansion of the zone of virus activity into regions that were not affected in the 1992-1993 epidemic. This is of major concern for the approximately 29 million Kenyans who are unvaccinated and therefore at risk of infection. A revision of the surveillance programme is underway to create a more efficient system of recognition of suspect YF cases, laboratory diagnosis and reporting to the appropriate authorities for action. In addition, a research programme to study YF ecology in Kenya will benefit the surveillance programme, enabling it to target potential 'hotspots' of YF activity. As it may not be possible, for financial reasons, to incorporate YF vaccination into the Kenya Expanded Programme of immunization in the immediate future, the need for continued surveillance to monitor the emergence of YF in Kenya is vital.