Rift Valley fever in humans in South Africa

Area of Science:

• Veterinary Medicine
• Epidemiology
• Virology

Background:

• Rift Valley fever (RVF) is a mosquito-borne viral disease that can cause severe illness in both animals and humans.
• An epizootic of RVF occurred in South Africa in 1974/1975, primarily affecting sheep and cattle, leading to a significant number of human cases.

Purpose of the Study:

• To document the epidemiology, clinical manifestations, and laboratory findings of human Rift Valley fever cases during the 1974/1975 epizootic.
• To assess the long-term seroprevalence of RVF antibodies in a population residing in affected areas.

Main Methods:

• Clinical and epidemiological data were collected from human patients.
• Laboratory confirmation included virus isolation and serological testing (antibody response).
• Follow-up serological studies were conducted in 1978 to determine immunity rates.

Main Results:

• Human infections were mainly acquired through handling infected animal carcasses; some cases were presumed to be mosquito-borne.
• Common complications included retinitis (20% of investigated patients) and meningoencephalitis (one fatal case).
• Laboratory confirmation was achieved in 110 cases; virus was isolated from fatal cases with hemorrhagic states and hepatitis.

Conclusions:

• Rift Valley fever poses a significant public health risk during epizootics, with direct contact with infected animals being a primary transmission route.
• The study highlights the potential for severe neurological and ocular complications, as well as hemorrhagic manifestations.
• Long-term immunity rates in affected populations suggest sustained exposure or endemicity following the epizootic.