Seroepidemiological Reconstruction of Long-term Rift Valley Fever Virus Circulation in Nouakchott, Mauritania

Although Rift valley fever (RVF) is endemic in Mauritania, with 8 epidemics documented since 1987, infections among human populations, particularly in Nouakchott, the capital city of Mauritania, remain limited. The objectives of the present study were to assess the seroprevalence of RVF in humans and reconstruct the epidemiological history of RVF virus (RVFV) circulation within the city.

Using data from a cross-sectional and descriptive serological study among asymptomatic subjects conducted in Nouakchott in 2021, a mathematical model was developed to trace the seroepidemiological evolution of RVFV between 1927 and 2020 in the capital city.

A total of 1319 participants were included, of whom 12.0% (158/1319) were positive for anti-RVFV immunoglobulin G (IgG). Sex, age group, district of residence, and use of mosquito nets or repellents at night were not statistically associated (P > .05) with anti-RVFV IgG positivity. Using the Hamiltonian Monte Carlo algorithm, posterior estimates of annual infection rates and probabilities of annual outbreak were calculated. The model suggested the absence of RVFV circulation before 1960, and the estimated outbreaks were concentrated between 1960 and 1972 and between 2017 and 2020.

The present study provides the first overview of the evolution of RVF epidemiology in Nouakchott and the serological evidence that RVFV has been circulating in human populations in Nouakchott for a longer period of time than previously thought. Therefore, close surveillance in animals, humans, and mosquito vectors is necessary to detect the presence of RVFV and interrupt any future epidemics in the country.