Rift Valley fever is a viral zoonosis caused by a Phlebovirus, first identified in 1931 during an investigation into an epidemic among sheep on a farm in the Rift Valley of Kenya [1][2]. The disease primarily affects animals but also has the capacity to infect humans, and it has been associated with significant morbidity, mortality and expanding geographical scope over recent decades [3].
Disease overview
Rift Valley fever
裂谷热
Evidence-backed informationEN 5/7 applicable sections · ZH 5/7 applicable sectionsUpdated Sep 3, 2026
Rift Valley fever (RVF) is an emerging, mosquito-borne viral zoonosis that primarily affects animals but also infects humans, with a clinical spectrum ranging from mild febrile illness to severe haemorrhagic disease [1][2][3]. First identified in 1931 during an epidemic among sheep in Kenya's Rift Valley, the virus has caused recurrent outbreaks across sub-Saharan and North Africa, and since 2000 has extended to the Arabian Peninsula [1][2]. In livestock, RVF causes high mortality in young animals and waves of abortion, producing substantial economic losses, while spillover to humans is driven largely by contact with infected animal tissues and by mosquito transmission [1][2][4].
Read the full clinical and epidemiological profile6
In humans, RVF incubation ranges from 2 to 6 days, and disease severity is highly variable [2]. The mild form presents as a febrile syndrome with sudden onset of flu-like fever, muscle pain, joint pain and headache, sometimes accompanied by neck stiffness, photophobia, anorexia and vomiting [2]. Severe disease can include haemorrhagic manifestations, hepatitis with jaundice, renal failure, encephalitis, partial blindness, and obstetric complications such as miscarriage, with a pooled case fatality around 21% in the more severe spectrum [3]. A systematic synthesis identified nine reported clinical syndromes—general febrile, renal, gastrointestinal, hepatic, haemorrhagic, visual, neurological, cardio-pulmonary and obstetric—with fever (approximately 81%) being the most common single manifestation [3].
Since its first identification in Kenya in 1931, RVF outbreaks have been reported across sub-Saharan Africa and North Africa, with major recorded events including the 1977 explosive outbreak in Egypt linked to infected livestock trade along the Nile irrigation system, the 1997–98 outbreaks in Kenya, Somalia and Tanzania following El Niño-related flooding, and the 2000 spread to Saudi Arabia and Yemen marking the first reported occurrence outside the African continent [1][2]. Human and animal outbreaks typically occur in connection with sustained animal epizootics, and the geographical scope of the disease has expanded to raise concern about further extension into Asia and Europe [1].
RVF virus is transmitted by several mosquito species, with the dominant vector varying by region; among animals, the virus is spread primarily by the bite of infected Aedes mosquitoes, and infected female mosquitoes can pass the virus directly to their eggs, producing new generations of infected mosquitoes [1]. Human infection occurs both through mosquito bites and, more commonly, through contact with the blood or organs of infected animals, and ingestion of unpasteurized or uncooked milk from infected animals has also been documented as a route [2]. No human-to-human transmission of RVF has been documented [2].
Outbreaks of RVF in animals can be prevented through a sustained programme of preventive animal vaccination using licensed modified live attenuated or inactivated veterinary vaccines, with the critical requirement that animal immunization be implemented before an outbreak begins; once an outbreak is underway, animal vaccination should not be initiated because multi-dose vials and reuse of needles and syringes can intensify transmission [1]. Restricting or banning livestock movement may help slow the spread of virus from infected to uninfected areas, and since animal outbreaks typically precede human cases, controlling RVF in animals is the principal means of preventing spillover to people [1]. For humans, an inactivated vaccine has been developed but remains unlicensed and unavailable commercially, having been used only experimentally to protect at-risk veterinary and laboratory personnel, and no specific treatment is available beyond early intensive supportive care for severe cases [1].
- 1World Health Organization. Rift Valley fever [Internet]. cited 4 Sept 2026.Available from: https://www.who.int/news-room/fact-sheets/detail/rift-valley-fever
- 2World Health Organization. Rift Valley fever [Internet]. cited 4 Sept 2026.Available from: https://www.who.int/health-topics/rift-valley-fever
- 3Anywaine Z et al. Clinical manifestations of Rift Valley fever in humans: Systematic review and meta-analysis. PLoS Negl Trop Dis. 2022 Mar. PMID: 35333856. doi: 10.1371/journal.pntd.0010233.PubMed: https://pubmed.ncbi.nlm.nih.gov/35333856/
- 4Weaver SC et al. Zika, Chikungunya, and Other Emerging Vector-Borne Viral Diseases. Annu Rev Med. 2018 Jan 29. PMID: 28846489. doi: 10.1146/annurev-med-050715-105122.PubMed: https://pubmed.ncbi.nlm.nih.gov/28846489/
- A92.4
- 1D47
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Literature links are provided for discovery and do not alter or validate the surveillance series above.
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Official sourcesAuthority, cadence, notes30
ECDC Surveillance Atlas — Belgium Annual Baseline
Belgium
Belgium annual Member-State reported case counts from the ECDC Surveillance Atlas. Missing topic/year cells remain unknown and published zeroes are preserved. Data provided by ECDC based on data reported by EU/EEA Member States.
ECDC Surveillance Atlas — Czechia Annual Baseline
Czechia
Czechia annual Member-State reported case counts from the ECDC Surveillance Atlas. Missing topic/year cells remain unknown and published zeroes are preserved. Data provided by ECDC based on data reported by EU/EEA Member States.
Germany RKI SurvStat 2.0
Germany
RKI SurvStat national weekly notification export; raw ZIP exports are retained and recent weeks are overwritten for revisions.
ECDC Surveillance Atlas — Estonia Annual Baseline
Estonia
Estonia annual Member-State reported case counts from the ECDC Surveillance Atlas. Missing topic/year cells remain unknown and published zeroes are preserved. Data provided by ECDC based on data reported by EU/EEA Member States.
ECDC Surveillance Atlas — Spain Annual Baseline
Spain
Spain annual Member-State reported case counts from the ECDC Surveillance Atlas. Missing topic/year cells remain unknown and published zeroes are preserved. Data provided by ECDC based on data reported by EU/EEA Member States.
ECDC Surveillance Atlas — France Annual Baseline
France
France annual Member-State reported case counts from the ECDC Surveillance Atlas. Missing topic/year cells remain unknown and published zeroes are preserved. Data provided by ECDC based on data reported by EU/EEA Member States.
ECDC Surveillance Atlas — United Kingdom Annual Baseline
United Kingdom
United Kingdom annual Member-State reported case counts from the ECDC Surveillance Atlas. Missing topic/year cells remain unknown and published zeroes are preserved. Data provided by ECDC based on data reported by EU/EEA Member States.
ECDC Surveillance Atlas — Greece Annual Baseline
Greece
Greece annual Member-State reported case counts from the ECDC Surveillance Atlas. Missing topic/year cells remain unknown and published zeroes are preserved. Data provided by ECDC based on data reported by EU/EEA Member States.
ECDC Surveillance Atlas — Croatia Annual Baseline
Croatia
Croatia annual Member-State reported case counts from the ECDC Surveillance Atlas. Missing topic/year cells remain unknown and published zeroes are preserved. Data provided by ECDC based on data reported by EU/EEA Member States.
ECDC Surveillance Atlas — Hungary Annual Baseline
Hungary
Hungary annual Member-State reported case counts from the ECDC Surveillance Atlas. Missing topic/year cells remain unknown and published zeroes are preserved. Data provided by ECDC based on data reported by EU/EEA Member States.
Ireland HPSC Notifiable Diseases Hub
Ireland
Ireland HPSC national weekly notifiable-disease totals from the official ArcGIS FeatureServer. Internal ingestion is enabled; public release remains disabled pending written redistribution permission.
Iceland Directorate of Health Annual Dashboard
Iceland
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Iceland Directorate of Health STI Dashboard
Iceland
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Iceland Directorate of Health Respiratory Dashboard
Iceland
ISO-week respiratory diagnosis counts. Hospitalizations, samples, and vaccination indicators are separate measures and are not counted as diagnoses.
Iceland Directorate of Health Historical Registry
Iceland
Historical official registry tables for 1997–2021, with annual totals and disease-specific monthly notification facts retained at source grain.
Iceland Directorate of Health Legacy ICD Monthly
Iceland
Historical Saga EHR ICD encounter counts for 1997–2020. This clinical measure is non-comparable with registry notifications and is kept separate.
ECDC Surveillance Atlas — Italy Annual Baseline
Italy
Italy annual Member-State reported case counts from the ECDC Surveillance Atlas. Missing topic/year cells remain unknown and published zeroes are preserved. Data provided by ECDC based on data reported by EU/EEA Member States.
JP NIID Weekly
Japan
Japan weekly infectious disease surveillance via NIID/JIHS.
Korea KDCA EID
South Korea
Korea KDCA notifiable infectious disease OpenAPI or portal/KOSIS downloads aggregated to national monthly notification counts.
ECDC Surveillance Atlas — Lithuania Annual Baseline
Lithuania
Lithuania annual Member-State reported case counts from the ECDC Surveillance Atlas. Missing topic/year cells remain unknown and published zeroes are preserved. Data provided by ECDC based on data reported by EU/EEA Member States.
ECDC Surveillance Atlas — Luxembourg Annual Baseline
Luxembourg
Luxembourg annual Member-State reported case counts from the ECDC Surveillance Atlas. Missing topic/year cells remain unknown and published zeroes are preserved. Data provided by ECDC based on data reported by EU/EEA Member States.
ECDC Surveillance Atlas — Latvia Annual Baseline
Latvia
Latvia annual Member-State reported case counts from the ECDC Surveillance Atlas. Missing topic/year cells remain unknown and published zeroes are preserved. Data provided by ECDC based on data reported by EU/EEA Member States.
ECDC Surveillance Atlas — Malta Annual Baseline
Malta
Malta annual Member-State reported case counts from the ECDC Surveillance Atlas. Missing topic/year cells remain unknown and published zeroes are preserved. Data provided by ECDC based on data reported by EU/EEA Member States.
ECDC Surveillance Atlas — Netherlands Annual Baseline
Netherlands
Netherlands annual Member-State reported case counts from the ECDC Surveillance Atlas. Missing topic/year cells remain unknown and published zeroes are preserved. Data provided by ECDC based on data reported by EU/EEA Member States.
Norway FHI MSIS Statistics Bank
Norway
Norway FHI MSIS national monthly notifications from the official Allvis frontend API; adapter contract checks guard the unversioned endpoint.
ECDC Surveillance Atlas — Poland Annual Baseline
Poland
Poland annual Member-State reported case counts from the ECDC Surveillance Atlas. Missing topic/year cells remain unknown and published zeroes are preserved. Data provided by ECDC based on data reported by EU/EEA Member States.
ECDC Surveillance Atlas — Romania Annual Baseline
Romania
Romania annual Member-State reported case counts from the ECDC Surveillance Atlas. Missing topic/year cells remain unknown and published zeroes are preserved. Data provided by ECDC based on data reported by EU/EEA Member States.
Sweden Public Health Agency SmiNet
Sweden
Sweden SmiNet national monthly reported cases from the official Public Health Agency statistics pages; public release is enabled with closed-month publication and revisable recent-month refreshes.
ECDC Surveillance Atlas — Slovenia Annual Baseline
Slovenia
Slovenia annual Member-State reported case counts from the ECDC Surveillance Atlas. Missing topic/year cells remain unknown and published zeroes are preserved. Data provided by ECDC based on data reported by EU/EEA Member States.
ECDC Surveillance Atlas — Slovakia Annual Baseline
Slovakia
Slovakia annual Member-State reported case counts from the ECDC Surveillance Atlas. Missing topic/year cells remain unknown and published zeroes are preserved. Data provided by ECDC based on data reported by EU/EEA Member States.