Interepidemic Rift Valley Fever Virus Seropositivity, Northeastern Kenya

Abstract

Most outbreaks of Rift Valley fever (RVF) occur in remote locations after fl oods. To determine environmental risk factors and long-term sequelae of human RVF, we examined rates of previous Rift Valley fever virus (RVFV) exposure by age and location during an interepidemic period in 2006. In a randomized household cluster survey in 2 areas of Ijara District, Kenya, we examined 248 residents of 2 sublocations, Gumarey (village) and Sogan-Godud (town). Overall, the RVFV seropositivity rate was 13% according to immunoglobulin G ELISA; evidence of interepidemic RVFV transmission was detected. Increased seropositivity was found among older persons, those who were male, those who lived in the rural village (Gumarey), and those who had disposed of animal abortus. Rural Gumarey reported more mosquito and animal exposure than Sogan-Godud. Seropositive persons were more likely to have visual impairment and retinal lesions; other physical fi ndings did not differ.

Rift Valley Fever Virus: A Real Bioterror Threat

“…Historically, while infections in humans are typically mild and present as selflimiting febrile illnesses, RVFV infections progress to more severe disease including fulminant hepatitis, encephalitis, retinitis, blindness, or a hemorrhagic syndrome in approximately 2% of affected individuals [20][21]. However, statistics from recent outbreaks suggest that the case fatality rate from RVFV infections is significantly increasing (>30%) in naive populations [1,14,[22][23]. For example, during the 2006-2007 Rift Valley fever outbreak in East Africa, RVF was diagnosed in over 1000 patients in multiple locations in Kenya, Somalia and Tanzania [24][25][26][27] and over 300 patients died [28].…”

Potential for Autoimmune Pathogenesis of Rift Valley Fever Virus Retinitis

“…5,6 Four groups were available for comparison: 1) persons with retinitis after exposure to RVFV (n = 8); 2) persons without retinitis after exposure to RVFV (n = 9); 3) persons with retinitis and no exposure to RVFV (n = 9); and 4) persons without retinitis and exposure to RVFV (n = 17). This study was approved by the institutional review boards at Case Western Reserve University and the Kenya Medical Research Institute.…”

“…Retinal complications occur in up to 10% of those affected and can cause lasting loss of vision. 6,[10][11][12] Other severe complications can include encephalitis (8%), hepato-renal failure, 8 hepatitis, 10 and hemorrhagic fever (1%).…”

“…Retinal complications occur in up to 10% of those affected and can cause lasting loss of vision. 6,[10][11][12] Other severe complications can include encephalitis (8%), hepato-renal failure, 8 hepatitis, 10 and hemorrhagic fever (1%). 11,13 Case-fatality rates have been reported as high as 31%, but the actual value is likely between 0.5% and 2% because a small proportion of infected persons are diagnosed, 11,13 especially those with milder disease.…”

“…Recent outbreaks have been documented in Saudi Arabia (2000) and the Horn of Africa (2006)(2007). [3][4][5][6][7][8][9] The most common severe complication of human RVFV infection is retinitis. Retinal complications occur in up to 10% of those affected and can cause lasting loss of vision.…”