Seroepidemiology of arboviruses among febrile patients in the Lake/River Basin Areas of Baringo, Naivasha and Tana, Kenya

Abstract

Background: Lassa fever is an acute, highly infectious viral haemorrhagic illness caused by Lassa fever virus. The reservoir is Mastomys natalensis. The disease is endemic in West African sub region causing 300,000-500,000 infections annually, with about 500 deaths. In March, 2012, we investigated a reported outbreak of Lassa fever in Taraba State, Nigeria to confirm the outbreak, determine its extent, characterize the outbreak and institute public health actions. Methods & Materials: We reviewed hospital records and used IDSR standard case definition for Lassa fever to identify and linelist cases. A suspected case was defined as “any person with severe febrile illness not responsive to the usual causes of fever in the area with or without sore-throat and at least one of the following: bloody stools, vomiting blood, bleeding into the skin and unexplained bleeding from the nose, vagina or eyes”. A standardized line-listing formwas developed to capture socio-demographic and clinical information of the cases. Various exposure factors including age, gender, occupation and contact history were examined. Results:A total of 35 caseswere recorded. Nine of 35 caseswere laboratory confirmed (25.7%). Altogether, 14 deaths were recorded giving a case fatality rate of 40%. Majority of the cases belonged to the age group 25-34 years (40%) with females constituting 51%. Most of the caseswere healthcareworkers (22.9%). The commonest presenting features were fever (85.7%), cough (28.6%), bleeding from orifices or into skin (25.7%) and headache (20%). In addition, the State’s Epidemic Management Committee was non-functional resulting in uncoordinated response to the outbreak. There were many exposure factors to Lassa fever such as over-crowding, drying of food items along high ways and bush burning and there was low index of suspicion of Lassa fever among health care workers. Conclusion: There was a confirmed outbreak of Lassa fever in Taraba State mostly affecting healthcare workers. Community sensitization and sensitization of health workers in Taraba State on Lassa fever were carried out. We recommended that the State should reactivate its Emergency Management Committee, surveillance of Lassa fever should be strengthened, Public/Health workers sensitization activities should be scaled up and records keeping should be improved.