Rift Valley fever

Rift Valley fever (RVF) is a notifiable condition. Human-to-human transmission has not been demonstrated; however, standard precautions should still be implemented.

Majority of patients are asymptomatic; however, patients may have a mild, self-limited illness with fever and liver abnormalities. Patients may have severe symptoms including ocular disease (10%), encephalitis (8%), or haemorrhagic fever (1%).[1]National Institute for Communicable Diseases. Healthcare workers guidelines on Rift Valley fever (RVF). Jan 2021 [internet publication]. https://www.nicd.ac.za/wp-content/uploads/2021/02/Rift-Valley-Fever-2021-Guidelines-for-Health-Care-Workers_110321.pdf [2]Jankovic J, Mazziotta J, Pomeroy S, et al. Bradley and Daroff's neurology in clinical practice, 2-volume set. 8th ed. Elsevier. 2021. The Rift Valley fever virus has also been demonstrated to result in miscarriage in a significant percentage of febrile pregnant women in endemic regions.[3]Baudin M, Jumaa AM, Jomma HJE, et al. Association of Rift Valley fever virus infection with miscarriage in Sudanese women: a cross-sectional study. Lancet Glob Health. 2016 Nov;4(11):e864-71. https://www.thelancet.com/journals/langlo/article/PIIS2214-109X(16)30176-0/fulltext http://www.ncbi.nlm.nih.gov/pubmed/27692776?tool=bestpractice.com

Supportive therapy is the standard of care as there are no specific antiviral treatments. Diagnostic approaches should be guided by the patient’s travel history to an endemic region (i.e., East Africa, West Africa, and Southern Africa) and exposure to livestock, particularly if the patient has slaughtered an animal or assisted in livestock birth in those areas.

A mild, usually self-limited infection caused by the Rift Valley fever virus (also known as RVFV). The virus belongs to the Bunyavirales order in the Phenuiviridae family (genus Phlebovirus). It is named after the Great Rift Valley in Kenya where it was first discovered in livestock in the early 1910s.[4]Murithi RM, Munyua P, Ithondeka PM, et al. Rift Valley fever in Kenya: history of epizootics and identification of vulnerable districts. Epidemiol Infect. 2011 Mar;139(3):372-80. http://www.ncbi.nlm.nih.gov/pubmed/20478084?tool=bestpractice.com [5]Daubney R, Hudson JR, Garnham PC. Enzootic hepatitis or Rift Valley fever. An undescribed virus disease of sheep, cattle and man from east Africa.1931;34(4):545-79. It is transmitted to humans by contact with the blood, other bodily fluids (e.g., amniotic fluid), organs, or drinking raw milk from infected animals (most commonly cows, sheep, goats, or camels).[6]Pepin M, Bouloy M, Bird BH, et al. Rift Valley fever virus (Bunyaviridae: Phlebovirus): an update on pathogenesis, molecular epidemiology, vectors, diagnostics and prevention. Vet Res. 2010;41:61. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2896810 http://www.ncbi.nlm.nih.gov/pubmed/21188836?tool=bestpractice.com Transmission also occurs via mosquito vectors including the Aedes and Culex species.[7]Tantely ML, Rakotoniaina JC, Tata E, et al. Biology of mosquitoes that are potential vectors of Rift Valley fever virus in different biotopes of the central highlands of Madagascar. J Med Entomol. 2013;50:603-10. http://www.ncbi.nlm.nih.gov/pubmed/23802456?tool=bestpractice.com [8]LaBeaud AD, Ochiai Y, Peters CJ, et al. Spectrum of Rift Valley fever virus transmission in Kenya: insights from three distinct regions. Am J Trop Med Hyg. 2007 May;76(5):795-800. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2367216 http://www.ncbi.nlm.nih.gov/pubmed/17488893?tool=bestpractice.com [9]Golnar AJ, Turell MJ, LaBeaud AD, et al. Predicting the mosquito species and vertebrate species involved in the theoretical transmission of Rift Valley fever virus in the United States. PLoS Negl Trop Dis. 2014 Sep 11;8(9):e3163. http://journals.plos.org/plosntds/article?id=10.1371/journal.pntd.0003163 http://www.ncbi.nlm.nih.gov/pubmed/25211133?tool=bestpractice.com The virus causes outbreaks of abortion and death of young livestock (most commonly sheep, goats, and cattle). Outbreaks in humans are often linked to direct exposure to livestock (epizootic outbreaks).[9]Golnar AJ, Turell MJ, LaBeaud AD, et al. Predicting the mosquito species and vertebrate species involved in the theoretical transmission of Rift Valley fever virus in the United States. PLoS Negl Trop Dis. 2014 Sep 11;8(9):e3163. http://journals.plos.org/plosntds/article?id=10.1371/journal.pntd.0003163 http://www.ncbi.nlm.nih.gov/pubmed/25211133?tool=bestpractice.com However, outside of large-scale outbreaks, the endemic transmission risk to humans remains a significant gap in epidemiology.[10]Gerken KN, LaBeaud AD, Mandi H, et al. Paving the way for human vaccination against Rift Valley fever virus: a systematic literature review of RVFV epidemiology from 1999 to 2021. PLoS Negl Trop Dis. 2022 Jan 24;16(1). https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8812886 http://www.ncbi.nlm.nih.gov/pubmed/35073355?tool=bestpractice.com

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