Rift Valley fever outbreaks are often triggered by unusually heavy rainfall and flooding events.

Health · Published 3 October 2026 Swipe more like this →

In short: Rift Valley fever is a viral disease that primarily cycles through mosquitoes and livestock, occasionally spilling over to humans. While most infections cause mild, flu-like symptoms, a small percentage of cases turn severe or even fatal. Understanding this zoonotic cycle is critical for managing its significant economic and health impacts.

Rift Valley fever (RVF) is caused by a virus found predominantly in sub-Saharan Africa, particularly in eastern and southern regions. The virus is primarily transmitted to humans through contact with the blood, body fluids, or tissues of infected animals, such as cows, sheep, goats, and camels. This often occurs during activities like slaughtering, butchering, or assisting with veterinary procedures, such as helping an animal give birth. While mosquito bites are a known transmission route for both animals and humans, there is no documented evidence of person-to-person spread.

The disease is intrinsically linked to environmental conditions. Outbreaks typically follow periods of excessive rainfall and flooding, which provide ideal conditions for mosquito eggs to hatch. The virus can be passed from female mosquitoes directly to their eggs, creating a reservoir that fuels new outbreaks. In livestock, the virus causes severe illness, including a high rate of pregnancy loss, which creates a major economic burden for communities reliant on animal products for income and sustenance.

For most humans, the infection manifests as a mild illness characterized by fever, weakness, back pain, and dizziness, with recovery typically occurring within two to seven days. However, about 8% to 10% of patients develop severe complications. These can include eye disease, which may lead to permanent vision loss, or inflammation of the brain (encephalitis). In less than 1% of cases, patients experience hemorrhagic fever, marked by jaundice and internal bleeding; approximately 50% of these patients die. Overall, the mortality rate for infected individuals is about 1%.

Currently, there is no licensed human vaccine for RVF, making prevention essential. Protective measures include wearing long sleeves, using insect repellent, and avoiding contact with the tissues of sick animals. While animal vaccines exist, they must be administered strategically; vaccinating during an active outbreak can sometimes exacerbate the situation. Because symptoms can mimic other illnesses, laboratory confirmation is necessary for accurate diagnosis, and medical care remains primarily supportive.

General information, not professional advice. Spotted an error? Flag the card or see corrections and complaints.

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