Rift Valley fever- Mauritania and Senegal

Between 20 September and 30 October 2025, a total of 404 confirmed human cases of Rift Valley fever (RVF), including 42 deaths, were reported by national health authorities in two West African countries: Mauritania and Senegal. RVF is a zoonotic disease, which mainly affects animals, but can also infect humans. The majority of human infections result from contact with the blood or organs of infected animals, but human infections have also resulted from the bites of infected mosquitoes. To date, no human-to-human transmission of RVF has been documented. While RVF often leads to severe illness in animals, its impact in humans varies, ranging from mild flu-like symptoms to severe hemorrhagic fever that can be fatal. RVF is endemic in both countries, where recurrent outbreaks have been previously reported in both livestock and humans. The risk of further spread remains high, especially with environmental conditions favorable to the proliferation of mosquitoes, periods of heavy rains and increased mosquito activity, as well as movements of livestock within country and towards Mali and Gambia for grazing and trade. The response to RVF outbreaks requires a One Health approach, based on enhanced collaboration between the human health, animal health and environmental sectors, in both countries and at the regional level. WHO, in collaboration with the World Organization for Animal Health (WOAH), and the Food and Agriculture Organization of the United Nations (FAO), currently assesses the overall risk as high at the national levels, moderate at the regional level and low at the global level.

Mauritania

Human cases: Between 27 September and 30 October 2025, a total of 46 confirmed human cases of RVF, including 14 associated deaths (case fatality ratio: 30%), were reported in eleven districts from thirteen regions (wilayas), three of which share international borders: Assaba (bordering Mali to the south), Brakna and Trarza (both bordering Senegal along the Senegal River). Out of a total of 190 samples tested, 46 were positive, i.e. a positivity rate of 24.2%.

Animal cases: On 30 October 2025, the Mauritanian Ministry of Animal Resources reported a total of 62 animal outbreaks, with 235 positive samples out of 1106 collected and tested. The first animal cases, involving goats and dromedaries, were reported in August 2025. A total of 235 animal cases, including 71 deaths (two in camels and 14 in goats), have been reported in Aioun (Hodh El Gharbi region) and Timbedra (Hodh Ech Chargui region), both located in the southeast near the border with Mali, as well as in Maghta Lahjar (Brakna region) in the center of the country. In the Brakna region, 46 animal cases and 55 deaths have been reported to WOAH. Affected species include sheep, goats, dromedaries and cattle.

RVF is endemic in Mauritania. The last major outbreak occurred in 2022, with 47 confirmed human cases, including 23 deaths (case fatality ratio 49%), mainly affecting pastoralists in nine of the fifteen regions. During this outbreak, cattle, camels and small ruminants were also affected, with positivity rates in animals approaching 21.2%.

Senegal

Human cases: Between 20 September and 30 October 2025, the Republic of Senegal reported a total of 358 confirmed human cases of RVF, including 28 deaths (case fatality rate: 7.8%). The cases were recorded in 22 health districts from eight administrative regions, with the vast majority (78%) reported in the Saint-Louis region. Additional cases have been reported in Dakar (nine cases), Fatick (12 cases), Kaolack (13 cases), Louga (18 cases), Matam (23 cases), Thiès (2 cases) and Tambacounda (2 cases). The affected districts in the Saint-Louis region, namely Dagana (32 cases), Pete (9 cases), Podor (32 cases), Richard-Toll (133 cases) and Saint-Louis (73 cases), are all located along the northern border with Mauritania, close to the Senegal River.

Animal cases: Animal infections have been detected in the same areas as human cases. On 23 September 2025, authorities collected 1122 blood samples and four abortion samples from small ruminant herds in the affected villages. Laboratory analyses confirmed 36 positive samples from six herds. As of 29 October 2025, a total of 160 confirmed animal cases of RVF have been reported in sheep, goats and cattle in seven regions of Senegal: Dakar, Fatick, Louga, Matam, Saint-Louis, Tambacounda and Thiès. In addition, 640 animal abortions were reported in three regions. As of 22 October 2025, the country has notified WOAH of 26 RVF outbreaks, affecting a total of 59 animals, including two deaths.

RVF is endemic in Senegal, with previous outbreaks affecting both human and animal populations. The last confirmed human case prior to this outbreak was reported in January 2025 in Touba, Diourbel region, while the last human case in the Saint-Louis region was in 2022.

Figure 1. Geographic distribution of confirmed human RVF cases (404) and deaths (n=42) in Mauritania and Senegal, September 20 to 30 October 2025.

Rift Valley fever (RVF) is a viral zoonotic disease primarily affecting domestic animals in sub-Saharan Africa, including cattle, sheep, goats and camels. Human infection may occur through bites from infected mosquitoes, however the majority of cases result from direct contact with the blood, tissues or organs of infected animals. Occupational groups at highest risk include livestock breeders, farmers, slaughterhouse workers and veterinarians. Humans can become infected by consuming unpasteurized or undercooked milk from infected animals. To date, no human-to-human transmission of RVF has been documented.

While RVF often leads to severe illness in animals, its impact in humans varies, ranging from mild flu-like symptoms to severe hemorrhagic fever that can be fatal. The majority of the infected individuals experience no symptoms or only mild illness, characterized by fever, general weakness, lower back pain and dizziness. However, a small percentage of patients (about 2%) progress to a severe form of the disease, which may manifest in one or more of the following three clinical presentations: ocular form (involving inflammation of the eye), meningoencephalitis (inflammation of the brain), and hemorrhagic form (bleeding). 

In both countries, multidisciplinary rapid response teams, comprising personnel from the ministries of health and veterinary services at both national and subnational levels, have been deployed to conduct thorough investigations and implement outbreak response measures. These efforts are being conducted in coordination with local authorities, ministries of agriculture and livestock, and partners, including WHO, FAO and WOAH.

In Senegal, as part of the response to the RVF outbreak, regional coordination teams have been set up in each affected region, using a One Health approach, with the designation of regional incident managers. A national response coordination unit has also set up a national incident management system, based on the same One Health framework.

WHO is providing support to Mauritania and Senegal, and is undertaking the following actions:

• Supporting countries in accelerating the rolling out of key priority interventions accordingly to their national plans: risk communication and community engagement (RCCE), deployment of SURGE and rapid response teams, briefing of clinicians, procurement and distribution of supplies, improved understanding of transmission dynamics.  
• Supporting surveillance activities and expanding diagnostic capacities at district level (including trainings) in human and animal health sectors, to minimize delayed detection, underreporting, and reliance on central PCR confirmation. 
• Organizing targeted training for health worker, community health workers and community-based animal health workers on RVF awareness and preventive measures, zoonotic and vector risks, case recognition and management as well as community engagement best practices. 
• Improving capacities for clinical care for severe patients through training, provision of supplies, and surge capacity as required. 
• Scaling up RCCE efforts significantly to focus on meaningful engagement with the most affected groups (e.g. herders, slaughterhouse workers) to raise awareness of transmission risks, preventive measures, care pathways, and access to trustworthy information. 
• Procuring and distributing medical, IPC and laboratory supplies based on country needs.
• Continuing investigation of transmission patterns, including examination of malaria circulation as well dual mapping of the human and animal outbreaks. 
• Supporting digital data management and production of updated, high-quality sitreps. 
• Scaling up vector-control activities, for RVF but also importantly against malaria and dengue. 
• Continuing partner coordination efforts with FAO, WOAH and other key operational partners and sectors.

FAO and WOAH are undertaking the following in support of national authorities:

• Providing personal protective equipment (PPE) for veterinary laboratories.
• Providing operational support on the ground to strengthen response activities in affected areas.
• Supporting countries with technical expertise and monitoring the animal situation in Senegal, Mauritania and in neighbouring countries.  
• Supporting community engagement by disseminating targeted messages to communities with exposure to livestock. 

The current outbreak of RVF in Senegal and Mauritania is unusual in its scale and severity, although both countries are endemic for the disease. It affects several districts in international border areas, particularly along the Senegal River, increasing the risk of inter-regional transmission due to animal movements. In Mauritania, RVF has been confirmed in eastern regions bordering Mali, raising concerns about potential regional spread beyond the Senegal River Basin through livestock movements.

A high proportion of severe human cases have been reported, potentially reflecting gaps in case detection and limitation in optimized clinical management. In Senegal, approximately 11% of confirmed human cases have presented with hemorrhagic symptoms, of which 20 have resulted in death. The situation is particularly concerning in Mauritania, where the case fatality rate has reached 30% indicating heightened severity.

As a result, the public health risk is assessed as high at the national level, moderate at the regional level and low at the global level. The risk to animal health is considered high at the national level, moderate at the regional level and low at the global level.

WHO, in collaboration with FAO and WOAH, has carried out a joint rapid risk assessment, which will be revised as new information becomes available.

RVF is a viral zoonotic disease primarily transmitted by mosquitoes, with transmission dynamics influenced by environmental factors (rainfall and floodings), which predominantly affects domestic animals such as cattle, sheep, camels and goats. Human cases usually occur in the vicinity of animal outbreaks, in areas with favorable conditions for mosquito transmission. The majority of human infections result from direct or indirect contact with the blood or organs of infected animals. Care should be taken when handling sick or dead animals, patients, or biological materials. It is recommended that a One Health approach be applied, integrating animal, human and environmental health efforts into all RVF prevention and control activities.

During outbreaks, countries need to strengthen their capacity to detect human cases early and ensure adequate patient care. Public awareness campaigns on the risks of RVF transmission and protective measures are essential to reduce infection and mortality rates.

Preventive measures for the public should focus on:

• Reducing the risk of animal-to-human transmission through safe livestock handling and slaughter practices. Maintaining good hand hygiene, including wearing gloves and protective equipment when handling sick animals or infected tissues, or during slaughter.
• Avoiding unsafe consumption of fresh blood, raw milk or animal tissue. In regions where epizootics are reported, all animal products (blood, meat, milk) must be thoroughly cooked before consumption.
• Preventing mosquito bites through vector control measures, including eliminating breeding sites, using insecticide-treated nets and repellents when possible, wearing long, light-colored clothing, and avoiding outdoor activities during peak mosquito activity hours.

Preventive measures at healthcare facilities should focus on:

Although human-to-human transmission of Rift Valley fever (RVF) has never been documented, health care workers caring for suspected or confirmed cases should follow standard precautions when providing care or handling biological samples.

Measures at the animal level should include:

• Considerations for restricting or banning livestock movement to help mitigate the risk of virus spread between infected and non-infected areas.
• Routine livestock vaccination before outbreaks to prevent epizootics. Vaccination should not be initiated once an outbreak has begun as use of multi-dose vials and reused needles/syringes could inadvertently contribute to virus spread.

WHO does not recommend any travel or trade restrictions to or from Mauritania and Senegal or affected regions based on the current information.

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Citable reference: World Health Organization (5 November 2025). Disease Outbreak News; Rift Valley fever in Mauritania and Senegal. Available at: https://www/who.int/emergencies/disease-outbreak-news/item/2025-DON584