Rift Valley fever epidemiology: shifting the paradigm and rethinking research priorities.

Rift Valley fever (RVF), a zoonotic mosquito-borne viral disease with erratic occurrence and complex epidemiology, results in substantial costs to veterinary and public health and national economies. Since 1985, RVF virus (RVFV) epidemiology has focused on epidemics triggered by flood-induced emergence of transovarially infected mosquitoes, following an interepidemic period during which RVFV persists primarily in floodwater Aedes spp mosquito eggs, with potential for low-level interepidemic circulation. In this Personal View, we challenge this classic framework of RVFV epidemiology, presenting instead a spectrum of RVFV dynamics ranging from epidemic to hyperendemic.

Localized Rift Valley fever virus persistence explains epidemic and interepidemic dynamics and guides control strategies.

Rift Valley fever (RVF) is an emerging disease with devastating impacts on livestock health and livelihoods. The risk of RVF virus (RVFV) emergence in new regions and the effectiveness of a strategy for preventing establishment are impacted by how infection persists at local scales. Multiple mechanisms have been proposed for its persistence in regions prone to epidemics, including maintenance via transovarial transmission (TOT) but whether and how TOT can support local persistence is not well understood.

Tanapox, South Africa, 2022.

Tanapox is a rarely diagnosed zoonosis known to be endemic to equatorial Africa. All previously reported human cases were acquired within 10° north or south of the Equator, most recently 19 years ago. We describe a human case of tanapox in South Africa (24° south of the Equator).

Exposure of South African Abattoir Workers to .

Abattoir workers may contract Q fever by inhalation of bacteria in aerosols generated by slaughtering livestock, or in contaminated dust. We estimated the seroprevalence of and examined the associated factors in a survey of South African abattoir workers. seropositivity was determined by detection of IgG antibodies against phase II antigen.

Rift Valley Fever Virus Seroprevalence among Humans, Northern KwaZulu-Natal Province, South Africa, 2018-2019.

We detected Rift Valley fever virus (RVFV) IgM and IgG in human serum samples collected during 2018-2019 in northern KwaZulu-Natal Province, South Africa. Our results show recent RVFV circulation and likely RVFV endemicity in this tropical coastal plain region of South Africa in the absence of apparent clinical disease.

Trends in the prevalence of microscopically-confirmed schistosomiasis in the South African public health sector, 2011-2018.

Background: Schistosomiasis, also known as bilharzia, is a chronic parasitic blood fluke infection acquired through contact with contaminated surface water. The illness may be mild or can cause significant morbidity with potentially serious complications. Children and those living in rural areas with limited access to piped water and services for healthcare are the most commonly infected.

Large-Scale International Validation of an Indirect ELISA Based on Recombinant Nucleocapsid Protein of Rift Valley Fever Virus for the Detection of IgG Antibody in Domestic Ruminants.

Diagnostic performance of an indirect enzyme-linked immunosorbent assay (I-ELISA) based on a recombinant nucleocapsid protein (rNP) of the Rift Valley fever virus (RVFV) was validated for the detection of the IgG antibody in sheep ( = 3367), goat ( = 2632), and cattle ( = 3819) sera. Validation data sets were dichotomized according to the results of a virus neutralization test in sera obtained from RVF-endemic (Burkina Faso, Democratic Republic of Congo, Mozambique, Senegal, Uganda, and Yemen) and RVF-free countries (France, Poland, and the USA). Cut-off values were defined using the two-graph receiver operating characteristic analysis.

Patterns of Rift Valley fever virus seropositivity in domestic ruminants in central South Africa four years after a large outbreak.

Rift Valley fever (RVF) is a mosquito-borne viral zoonosis showing complex epidemiological patterns that are poorly understood in South Africa. Large outbreaks occur in the central interior at long, irregular intervals, most recently in 2010-2011; however, the level of herd immunity of ruminant livestock, a key determinant of outbreaks, is unknown. During 2015-2016 a cross-sectional study on 234 randomly-selected farms investigated the prevalence, patterns of, and factors associated with, antibodies to RVF virus (RVFV) in livestock in an area heavily affected by that outbreak.

Evaluation of Diagnostic Performance of Three Indirect Enzyme-Linked Immunosorbent Assays for the Detection of IgG Antibodies to Ebola Virus in Human Sera.

Filovirus serological diagnosis and epidemiological investigations are hampered due to the unavailability of validated immunoassays. Diagnostic performance of three indirect enzyme-linked immunosorbent assays (I-ELISA) was evaluated for the detection of IgG antibody to Ebola virus (EBOV) in human sera. One I-ELISA was based on a whole EBOV antigen (WAg) and two utilized recombinant nucleocapsid (NP) and glycoproteins (GP), respectively.

Rift Valley Fever Virus Exposure amongst Farmers, Farm Workers, and Veterinary Professionals in Central South Africa.

Rift Valley fever (RVF) is a re-emerging arboviral disease of public health and veterinary importance in Africa and the Arabian Peninsula. Major RVF epidemics were documented in South Africa in 1950⁻1951, 1974⁻1975, and 2010⁻2011. The number of individuals infected during these outbreaks has, however, not been accurately estimated.

Rift Valley Fever Reemergence after 7 Years of Quiescence, South Africa, May 2018.

Phylogenetic analysis of Rift Valley fever virus partial genomic sequences from a patient infected in South Africa in May 2018 suggests reemergence of an endemic lineage different from that of the epidemic in South Africa during 2010-2011. Surveillance during interepidemic periods should be intensified to better predict future epidemics.

Human Cases of Rift Valley Fever in South Africa, 2018.

Major Rift Valley fever (RVF) epidemics in South Africa occur at irregular intervals, usually spanning several decades, with human cases rarely reported in the absence of widespread outbreaks in livestock. This report describes four cases of RVF in farm workers associated with an isolated outbreak on a sheep farm in the Free State Province of South Africa, in 2018. In contrast to the last major RVF epidemic in South Africa in 2010-2011, where detection of human cases served as an alert for an ongoing outbreak in livestock, the current isolated outbreak was first detected in livestock, and human cases recognized following subsequent epidemiological investigation.

Impact of rotavirus vaccine on childhood diarrheal hospitalization after introduction into the South African public immunization program.

Background: Oral rotavirus vaccine was introduced into the South African routine immunization program in August 2009 administered at 6 and 14 weeks with no catch-up. We described the change in rotavirus-associated diarrheal hospitalizations among children <5 years at 3 sentinel sites from 2009 through 2011.

Methods: During 2009 through 2011, we compared the proportion of enrolled children aged <5 years hospitalized with acute gastroenteritis and testing rotavirus positive.

Integration of preventing mother-to-child transmission of HIV and syphilis testing and treatment in antenatal care services in the Northern Cape and Gauteng provinces, South Africa.

Background: South Africa recommends universal syphilis and HIV testing in pregnancy, with prompt antiretroviral therapy or penicillin treatment for women testing positive.

Methods: We used a multistage, purposeful sampling strategy to retrospectively identify clinical records from a sample (7.3%) of 32,518 women delivering from January 2005 to June 2006 at 6 public clinics in the Northern Cape and Gauteng.