Outbreak of Rift Valley Fever in Kenya

Jun 25, 2018 | Lindsay Bonesteel | Outbreak News


Since the beginning of June, Kenya has been experiencing an outbreak of Rift Valley Fever (RVF) with 26 reported human cases and six deaths [1]. The first human case of RVF was laboratory-confirmed on June 7, 2018 [2]. This is the first RVF outbreak in Kenya since a 2006-2007 outbreak killed 234 people [3]. As of June 16th, twenty-four cases, and all six deaths, have been reported in Wajir County, with the remaining two cases occurring in Marsabit County [1]. Additionally, an estimated 50 animals, primarily camels and sheep, have died from RVF since the beginning of June [3].


Rift Valley Fever, which most commonly occurs in livestock, including sheep, goats, cattle, and camels, can be transmitted to humans in a few different ways [5,6]. Most human cases of RVF are the result of contact with the blood or tissue of an infected animal, often through slaughtering, butchering or veterinary procedures [6]. RVF can also be transmitted through the bite of an infected mosquito. However, there is no record of human-to-human transmission of RVF. 


Most people who contract RVF experience mild symptoms, including fever, headache, and muscle and joint pain, typically lasting between two and seven days [6,7]. However, a small percentage of people will develop more severe symptoms. Approximately 0.5% to 2% of patients will develop ocular disease [6]. While it is rare to die of this form of the disease, 50% of patients who develop lesions in the macula of the eye will experience permanent vision loss. Two other serious forms of the disease include encephalitis and hemorrhagic fever, with each affecting less than 1% of patients [7]. Symptoms of the encephalitic form include severe headaches, hallucinations, lethargy, disorientation, and coma [6]. Most RVF fatalities are the result of the hemorrhagic fever form. These patients usually develop symptoms within two to four days of the onset of the disease. The earliest symptom is usually jaundice, and may be followed by vomiting blood, blood in feces, bleeding from the nose and gums, and a purpuric rash. The case-fatality ratio for this form of the disease is 50%, with death occurring within three to six days after developing symptoms. There is no specific treatment for RVF.


Outbreaks of RVF most often occur after a period of heavy rainfall, which allows mosquito populations to thrive [8]. The earliest evidence of an outbreak in animals is usually a large number of abortions in domesticated animals [6]. For infected sheep, the rate of abortion is nearly 100%. RVF also has a high mortality rate in young animals [6,8]. Animal vaccination can be used to control the disease before an outbreak occurs. However, a vaccination campaign is not recommended during an outbreak, as this could worsen the outbreak if proper procedure is not followed [6]. A human RVF vaccine has been developed, but it is not licensed or available commercially [6].


The Kenyan government has implemented several measures in an effort to control the current outbreak. Four isolation centers have been set up in infected areas, and vector control measures are in place, including insecticide spraying [1,2]. Additionally, the slaughter of uninspected animals has been banned in Wajir County [2]. The Ministry of Health urges Kenyans to remain on alert and report to a health facility if they suspect they may have the disease.





[1] http://www.who.int/csr/don/18-june-2018-rift-valley-fever-kenya/en/

[2] http://www.health.go.ke/press-release-on-disease-outbreak-situation-in-k...

[3] https://www.reuters.com/article/us-kenya-health/kenyan-official-says-fiv...

[4] http://apps.who.int/iris/bitstream/handle/10665/272848/OEW24-815062018.pdf

[5] https://www.cdc.gov/vhf/rvf/index.html

[6] http://www.who.int/news-room/fact-sheets/detail/rift-valley-fever

[7] https://www.cdc.gov/vhf/rvf/symptoms/index.html

[8] http://www.oie.int/doc/ged/D13962.PDF

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