Signs and Symptoms
RVF virus has an incubation period of 2-6 days following infection and can cause several different disease syndromes. Most commonly, people with RVF have either no symptoms or a mild illness associated with fever and liver abnormalities. Patients who become ill usually experience fever, generalized weakness, back pain, and dizziness at the onset of the illness. Typically, patients recover within two days to one week after onset of illness.
However, a small percentage (8-10%) of people infected with RVFV develop much more severe symptoms, including:
- Ocular disease (diseases affecting the eye), which sometimes accompanies the mild symptoms described above. Lesions on the eyes may occur 1-3 weeks after onset of initial symptoms with patients reporting blurred and decreased vision. For many patients, lesions disappear after 10-12 weeks; however, for those with lesions occurring in the macula, approximately 50% of patients will have permanent vision loss.
- Encephalitis, or inflammation of the brain, which can lead to headaches, coma, or seizures. This occurs in less than 1% of patients and presents 1-4 weeks after first symptoms appear. Though death from this is rare, neurological deficits, sometimes severe, may persist.
- Hemorrhagic fever, which occurs in less than 1% of overall RVF patients, but fatality for those who do develop these symptoms, is around 50%. Symptoms of hemorrhaging may begin with jaundice and other signs of liver impairment, followed by vomiting blood, bloody stool, or bleeding from gums, skin, nose, and injection sites. These symptoms appear 2-4 days and death usually occurs 3-6 days after.