Rift Valley fever (RVF): a re-emerging zoonotic disease, pathogenesis, epidemiology, current status, and future perspective – correspondence

Dear Editor, Rift Valley fever (RVF) is a re-emerging zoonotic disease that is spread by mosquitoes and is characterized by the Rift Valley fever virus (RVFV). More than 30 different species of mosquitoes, representing at least six different genera, are carriers of the RVF virus, such as Aedes, Culex, Anopheles, Eretmapodites, Mansonia, and Coquillettidia. The fact that the virus has been extracted from mosquitoes and the eggs they lay in a variety of distinct mosquito species hints at the existence of multiple transmission pathways1. This infection might produce severe conditions and mostly affects cattle and other domestic animals (such as cattle, buffalo, sheep, goats, and camels). Many scientific research reports that this pathogen is often found in parts of eastern and southern Africa. However, it may also be encountered in the majority of nations in sub-Saharan Africa, Madagascar, Saudi Arabia, and Yemen. This infection affects both humans and animals. Previous RVF epidemics have been significant public health catastrophes in the nations and have impacted human health. So, the WHO deems the infection to be a concern for investigation and action in order to combat another epidemic. Concerns about an increase in cases of RVF in cattle and people throughout Africa during the current coronavirus disease 2019 epidemic have grown in the last couple of years. Before 1975, RVF was thought to be a disease that only affected animals in Africa. Cases in humans were uncommon, and those affected by RVF had seen modest clinical symptoms2. In South Africa in 1975, Egypt in 1977, and Mauritania in 1987, severe hemorrhagic fever outbreaks were recorded, along with cases of the disease and mortality in people. In December 1997, one of the most notable outbreaks occurred in East Africa. At that time, inexplicable human fatalities were recorded in the northeastern district of Kenya and southern Somalia. These locations were both affected by the epidemic. This pandemic was regarded as the most catastrophic that had ever occurred in the area. In September of 2000, RVF was discovered for the first time outside of the African continent in Saudi Arabia and Yemen. This discovery resulted in the loss of human life and significant cattle population. Kenya was deemed to be experiencing an epidemic in 2006–2007. The next countries to be hit were Tanzania and Somalia. Overall, 2007 and 2008 were devastating years for Madagascar and South Africa3,4. Burundi is now experiencing the first-ever epidemic of RVF in the nation and hurting livestock, which is both an essential source of revenue and an important factor in ensuring food security and adequate nutrition. In April 2022, the first known instances were discovered. As of June 2022, the incidence of morbidity and mortality among animals was fast climbing upward5,6. Besides, a total of 47 patients were diagnosed with RVF recorded from nine of Mauritania’s 15 wilayas between 30 August and 17 October 2022. The majority of those affected were animal operators. Among those affected, there were 23 fatalities (regions). In eight of Mauritania’s regions, or wilayas, the virus that triggers RVF in animals (including camels, cattle, and small ruminants) is circulating. In all, 12 wilayas have documented recognized instances of the disease in either humans or animals7. RVFV is classified as a member of the family Bunyaviridae, genus Phlebovirus, and belonging to the genus Bunyavirus are contain a single-stranded RNA genome with three segments. The cytoplasm is the site of transcription and replication. Three glycoproteins (Gn and Gc) and a viral nucleocapsid protein (N) are encoded by the medium-sized (M) genome segment of bunyaviruses, whereas the smallest (S) segment encodes the viral polymerase (L). Aside from the structural proteins, RVFV also generates three nonstructural proteins, one expressed on the S segment, one encrypted on the M segment (a 78 kDa protein and a 14 kDa protein that we recommend calling NSm1 and NSm2), and one expressed on both segments (termed NSs). These nonstructural proteins do not contribute to viral replication in cell culture but are essential for pathogenesis in living organisms8–10. RVF is most often transmitted to humans by direct contact with the blood, bodily fluids, or tissues of infected animals, most commonly domesticated animals such as cattle, sheep, goats, buffalo, and camels11. This kind of close interaction may happen when animals are being slaughtered or butchered, caring for ill animals, aiding animals with veterinary operations like giving birth, and consuming raw or undercooked animal products. RVF may also be transmitted to humans by the bites of infected mosquitoes and, less often, through the bites of other types of biting insects. Infection with the RVFV has been shown to have happened in labs due to the inhalation of virus particles in the air (known as aerosol transmission). It has not been demonstrated that the virus may pass from one individual to another. There have been no recorded cases of the virus being passed on to medical personnel despite using standard safeguards for infection control12,13. The confirmed diagnosis of RVF can only be made by laboratory testing of blood or other tissue specimens. Virus isolation in cell culture and several molecular methods may be used to confirm the presence of the pathogen and blood samples taken during an infection. The most useful experiment is reverse transcriptase-PCR test. Besides, antibody experiments with enzyme-linked immunoassay can also be employed to affirm the presence of RVFV pathogen by demonstrating the appearance of immunoglobulin M antibodies, which emerge momentarily as an effective response to a persistent infection and immunoglobulin G antibodies13,14. RVF has no proven therapy that the Food and Drug Administration has authorized. Most occurrences of RVF are minor and resolve on their own. Typical over-the-counter drugs are effective in treating the symptoms of minor sicknesses, such as fever and body pains. In most cases, the recovery period from the majority of illnesses is between 2 days and 1 week. Sometimes hospitalization is necessary, and when it is, only supportive care is provided for more severe instances15. RVF currently has no possible pharmaceutical that may treat the condition affecting people. The global policymaker should adopt the necessary actions to establish a treatment to combat this re-emerging zoonotic infection, and they should invest more money in scientific research to discover a viable vaccine or medicine. Ethical approval Not applicable. Sources of funding Not applicable. Author contribution S.A.: conceptualization and writing – original draft preparation; M.M.R. and M.R.I.: writing and editing; M.R.: writing, editing, and supervision. All authors have reviewed and approved the final version of the manuscript prior to submission. Conflicts of interest disclosure The authors declare no conflicts of interest, financial or otherwise. Research registration unique identifying number (UIN) None. Guarantor M.M.R. (corresponding author), take full responsibility for the work and/or the conduct of the study, had access to the data and controlled the decision to publish. Data availability All data are available within the manuscript.