Open Outbreak

Rift Valley fever

También conocido como: RVF, Rift Valley fever virus

Rift Valley fever is a virus infection that mainly affects livestock such as sheep, goats, cattle and camels, but it can also make people sick. Most human infections happen after contact with the blood, organs or other tissues of infected animals. Mosquito bites can also spread it. WHO said in 2025 that no human-to-human transmission has been documented. In people, illness ranges from a short flu-like illness to dangerous complications including bleeding, brain inflammation and eye disease. WHO outbreak reports show that overall severity can vary a lot by place and year: some outbreaks have low death rates, while others have reported much higher case fatality among confirmed cases. There is no specific antiviral treatment in the sources found here; care is supportive. A human vaccine has been developed but, in the sources used here, it is not licensed or commercially available. The disease is mainly reported in Africa and has also caused outbreaks in the Arabian Peninsula.

Datos clave

TransmisiónContact with blood, tissues or organs of infected animals; bites from infected mosquitoes; raw or unpasteurized animal products are also described. No human-to-human transmission has been documented in the WHO source used here.
Incubaciónunknown
LetalidadVaries by outbreak and severity. WHO reported overall case fatality usually tends to be less than 1% in documented outbreaks, but recent confirmed-case outbreaks were much higher in some settings, including 49% in Mauritania in 2022 and 30% in Mauritania and 7.8% in Senegal in 2025.
Número reproductivounknown
VacunaA human vaccine has been developed but is not licensed or commercially available in the sources used here. Animal vaccination is used for prevention.
TratamientoNo specific treatment in the sources used here; supportive care.
ReservorioLivestock are major amplifying hosts. The encyclopedia source also describes mosquitoes as vectors and mentions bats as possible reservoirs.
Regiones endémicasMainly sub-Saharan Africa; outbreaks have also occurred in the Arabian Peninsula.

Transmission

Rift Valley fever is mainly a disease of animals, and people usually catch it from infected livestock rather than from other people. WHO reported in 2025 that most human infections result from contact with the blood or organs of infected animals. This can happen during herding, slaughter, butchering, veterinary work or handling animal births and abortions. WHO also said people can be infected by bites from infected mosquitoes. The encyclopedia source adds other possible exposures, including breathing in infectious material around animal slaughter and drinking raw milk from infected animals. WHO stated in the 2025 outbreak report that no human-to-human transmission has been documented. That matters because it means the main risk is exposure to infected animals and mosquito-heavy environments, especially after heavy rains and flooding, rather than casual contact with a sick person.

Symptoms and severity

Rift Valley fever in people can be mild, but it can also become severe. The encyclopedia source describes common early symptoms such as fever, headache and muscle pain, often lasting up to about a week. It also describes more serious complications, including eye disease with loss of sight, brain inflammation causing confusion and severe headache, and bleeding with liver problems. WHO's 2025 report says the clinical picture ranges from mild flu-like illness to severe haemorrhagic fever that can be fatal. How dangerous an outbreak is can differ a lot by year and place. WHO's 2018 Kenya report said the overall case fatality ratio in documented outbreaks tends to be less than 1%, but recent WHO notices also show much higher figures among confirmed cases in some outbreaks, including 23 deaths among 47 confirmed cases in Mauritania in 2022 and 42 deaths among 404 confirmed cases across Mauritania and Senegal in 2025.

Treatment and vaccines

The sources used here do not describe a proven specific antiviral treatment for Rift Valley fever in routine use. The encyclopedia source says treatment is supportive care. In plain language, that means treating the person's symptoms and complications, such as dehydration, bleeding, organ problems or brain involvement, while the body fights the infection. Prevention is therefore especially important. The encyclopedia source says vaccination of animals can help prevent human disease, but it also notes this should be done before an outbreak rather than in the middle of one. For people, the same source says a human vaccine has been developed but is not licensed or commercially available. WHO's outbreak reports focus on reducing mosquito bites, safe handling of animal products, better animal and human surveillance, and coordination between public health and veterinary services. Those measures fit the fact that this is a disease shared between animals, mosquitoes and people.

Where it occurs

Rift Valley fever is mainly reported in Africa, especially in areas where livestock, mosquitoes and periods of heavy rain overlap. The encyclopedia source says outbreaks have occurred in Africa and Arabia. WHO notices returned in this session show recent or past events in Mauritania, Senegal, Kenya, Sudan, Niger, Gambia, Madagascar, South Africa, Tanzania, Saudi Arabia, Yemen and Mayotte. WHO's 2025 report says the disease is endemic in both Mauritania and Senegal. WHO's 2019 Sudan report says it is endemic in Sudan, and the 2021 Kenya report describes recurrent outbreaks there. A 2016 WHO notice also recorded cases in China, but that item reflects detection rather than established endemic circulation. For a general reader, the key point is that RVF is not everywhere all the time. It tends to appear where infected animals and suitable mosquitoes are present, often after unusual rain or flooding that increases mosquito numbers.

Recent history

This site's archive count for this disease is 21 WHO notices since 1996. The WHO items returned here show that Rift Valley fever keeps reappearing rather than causing one continuous global wave. The notices span East, West and southern Africa, plus the Arabian Peninsula, with events in Kenya and Somalia in 1998, Saudi Arabia and Yemen in 2000, Tanzania in 2007, Madagascar in 2008, South Africa in 2010, Mauritania in 2012, Niger in 2016, Gambia in 2018, Kenya and Mayotte in 2019, Sudan in 2019, Mauritania in 2020 and 2022, Kenya in 2021, and Mauritania and Senegal in 2025. WHO's 2025 report is especially notable for scale: 404 confirmed human cases and 42 deaths across two neighboring countries. WHO assessed the overall risk in that event as high at the national level, moderate at the regional level and low at the global level.

What to watch

The main warning signs are the ones WHO keeps linking to outbreak growth. First is spread into new regions, especially across borders through livestock movement. WHO's 2025 report highlighted border districts along the Senegal River and the risk of inter-regional spread. Second is weather that favors mosquitoes, especially heavy rain, flooding and mass mosquito emergence; WHO linked these conditions to outbreaks in Kenya, Sudan, Gambia and the 2025 West Africa event. Third is widening animal infection, including abortions and illness in sheep, goats, cattle or camels, because human outbreaks often follow animal transmission. Fourth would be any credible evidence of human-to-human spread, which WHO says has not been documented so far. Fifth is vaccine availability for animals and any change in the status of a human vaccine, which is not licensed in the sources used here. A larger concern would be repeated severe outbreaks with high confirmed-case fatality in new areas.

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