In late September 2025, Senegal witnessed one of its most severe outbreaks of Rift Valley fever (RVF) in years. This zoonotic disease has affected over 350 people in Senegal alone, with 28 confirmed deaths, while neighbouring Mauritania reported 46 cases and 14 fatalities. The outbreak primarily affects communities along the Senegal River, where heavy rains have created ideal breeding grounds for mosquito vectors spreading the virus. The situation prompted Senegal to launch a nationwide multisectoral response involving the health, agriculture, environment, and water ministries to control the outbreak through surveillance, mosquito control, and livestock vaccination.
What is Rift Valley Fever?
Rift Valley fever (RVF) is a viral disease that primarily affects livestock and wild animals, though it can also infect humans. The disease is caused by the Rift Valley fever virus, a member of the Phlebovirus genus. First identified in 1931 in Kenya’s Rift Valley region, this zoonotic disease has since spread across Africa, the Arabian Peninsula, and occasionally poses global health concerns.
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The virus is transmitted mainly through mosquitoes, particularly Aedes and Culex species. During heavy rainfall and flooding, mosquito populations increase dramatically, creating ideal conditions for the virus to spread. Humans can also contract RVF through direct contact with infected animal blood or tissue, or by consuming unpasteurized dairy products from infected animals.
Symptoms of Rift Valley Fever
In humans, the incubation period for RVF typically ranges from 2 to 6 days. Most human infections are mild, presenting with symptoms such as:
- Sudden onset of fever
- Muscle pain (myalgia)
- Headache
- Dizziness
- Joint pain (arthralgia)
- Nausea and vomiting
A small proportion of infected individuals develop more severe manifestations of the disease, which can appear in three distinct forms:
- Hemorrhagic fever: The most severe form, occurring in about 1–2% of symptomatic cases. Symptoms can include jaundice, vomiting blood, bloody diarrhea, and bleeding from the nose, mouth, or other openings. This form carries a high mortality rate.
- Encephalitis: Inflammation of the brain leading to symptoms such as severe headache, confusion, drowsiness, tremors, and convulsions. Recovery may be prolonged, and some individuals might experience long-term neurological effects.
- Ocular disease: Lesions in the retina can result in diminished vision or blindness. This condition is often painless and may go unnoticed until vision is significantly affected.
In animals, RVF causes high rates of abortion and mortality, particularly among young livestock.
How is Rift Valley Fever treated?
There is no specific antiviral treatment for RVF. Management focuses on supportive care to relieve symptoms and prevent complications, based on WHO and CDC guidelines.
- Supportive care: Rest, hydration, and pain relievers such as acetaminophen for fever and aches. Hospitalization may be required for severe cases.
- Complication management: Blood transfusions or clotting factors for hemorrhagic cases, and anti-inflammatory drugs or intensive care for encephalitis.
- Prevention during outbreaks: Infected individuals should avoid mosquito exposure to prevent further transmission.
Early diagnosis through blood tests is essential for timely intervention.
Difference Between Valley Fever and Rift Valley Fever
Valley fever and Rift Valley fever are completely different diseases caused by distinct pathogens and transmitted in different ways.
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Valley fever (coccidioidomycosis) is a fungal infection caused by inhaling spores of Coccidioides species found in arid soil, particularly in the southwestern United States, Mexico, and parts of Central and South America. It is not contagious and spreads when contaminated soil is disturbed and spores become airborne. Symptoms often resemble the flu, and most cases resolve without treatment, though some may progress to severe disease.
Rift Valley fever, in contrast, is a viral disease caused by the Rift Valley fever virus (RVFV), primarily affecting livestock and humans in Africa and the Arabian Peninsula. It spreads mainly through mosquito bites or contact with infected animal tissues and fluids. Human symptoms range from mild flu-like illness to severe complications such as hemorrhagic fever, encephalitis, and eye disease. Unlike Valley fever, Rift Valley fever can cause large outbreaks in both animals and humans, especially after heavy rainfall and flooding.
Prevention tips for Rift Valley Fever
- Use personal protective equipment (PPE) when handling or slaughtering animals, including gloves, long sleeves, and eye protection.
- Practice strict hand hygiene and avoid contact with blood, tissues, or bodily fluids from potentially infected animals.
- Consume only pasteurized dairy products and thoroughly cook meat.
- Vaccinate livestock where approved and maintain vaccination records.
- Implement vector control to reduce mosquito populations by eliminating standing water, using approved insecticides, and installing bed nets or window screens.
- Enforce movement controls and surveillance of livestock during outbreaks.
- Report suspected human or animal cases promptly to health or veterinary authorities.
