Risk Factors for Severe Rift Valley Fever Infection in Kenya, 2007

Abstract

Abstract. A large Rift Valley fever (RVF) outbreak occurred in Kenya from December 2006 to March 2007. We conducted a study to define risk factors associated with infection and severe disease. A total of 861 individuals from 424 households were enrolled. Two hundred and two participants (23%) had serologic evidence of acute RVF infection. Of these, 52 (26%) had severe RVF disease characterized by hemorrhagic manifestations or death. Independent risk factors for acute RVF infection were consuming or handling products from sick animals (odds ratio [OR] = 2.53, 95% confidence interval [CI] = 1.78-3.61, population attributable risk percentage [PAR%] = 19%) and being a herdsperson (OR 1.77, 95% CI = 1.20-2.63, PAR% = 11%). Touching an aborted animal fetus was associated with severe RVF disease (OR = 3.83, 95% CI = 1.68-9.07, PAR% = 14%). Consuming or handling products from sick animals was associated with death (OR = 3.67, 95% CI = 1.07-12.64, PAR% = 47%). Exposures related to animal contact were associated with acute RVF infection, whereas exposures to mosquitoes were not independent risk factors.

Cross-Sectional Survey of Rift Valley Fever Virus Exposure in Bodhei Village Located in a Transitional Coastal Forest Habitat in Lamu County, Kenya

“…The age discrepancy in seroprevalence (over and under the age of 15 years old), as noted by others, 17 suggests that occupational exposure to RVFV through aerosolized transmission rather than mosquito vector-borne transmission is the predominant source of RVFV exposure in Bodhei and elsewhere in Kenya. 2 Transmission in non-arid areas has been previously documented in Kenya and other endemic countries of Africa. Within Kenya, significant human and animal RVF outbreaks have occurred in the Lake Naivasha, Lake Baringo, and Kilifi areas.…”

“…The two predominant modes of RVF virus (RVFV) transmission to humans are through mosquito bites and contact with infected livestock. 1,2 In humans, RVFV-related disease usually presents with headache, fever, and malaise but can progress to much more severe manifestations that include retinitis, encephalitis, or hemorrhagic fever. 2,3 The overall fatality rate is estimated at 0.5-1%.…”

“…1,2 In humans, RVFV-related disease usually presents with headache, fever, and malaise but can progress to much more severe manifestations that include retinitis, encephalitis, or hemorrhagic fever. 2,3 The overall fatality rate is estimated at 0.5-1%. However, among patients whose clinical illness is sufficiently severe to bring them to the attention of medical personnel, mortality has been reported to be as high as 29%, which was seen during the Kenya 2006-2007 outbreak.…”

Rift Valley Fever Virus Vaccine Lacking the NSs and NSm Genes Is Safe, Nonteratogenic, and Confers Protection from Viremia, Pyrexia, and Abortion following Challenge in Adult and Pregnant Sheep

“…mosquitoes) that are more likely to feed on humans. Second, the high virus loads found in livestock are also a significant risk factor for human infection by direct contact with contaminated blood, tissues, and aborted fetal materials (1). A vaccination strategy targeted at preventing the virus amplification step in livestock could provide a window of opportunity to interrupt nascent RVFV outbreaks by both reducing the potential for secondary vector spillover and eliminating the threat posed by infected livestock tissues.…”

Characterization of Wild-Type and Alternate Transcription Termination Signals in the Rift Valley Fever Virus Genome

“…Initially confined to sub-Saharan regions of Africa, where periodic epidemics and epizootics have occurred, RVF spread to Egypt in 1977 and to the Middle East in 2000, representing a high risk to other regions (reviewed in references 23, 26, and 29). Following unusual climatic conditions, outbreaks have occurred between 2006 and 2008 in Kenya, Tanzania, and Sudan as well as in Madagascar and Mayotte, resulting in numerous human and animal deaths (2,3,24,27,33). In 2010, serious outbreaks occurred in South Africa and in Mauritania.…”