Mapping the Risk for West Nile Virus Transmission, Africa

Abstract

W est Nile virus (WNV) is one of the most widespread of the arboviruses because of the translocation of the virus by migratory birds (1-3). Since its initial detection in Uganda in 1937 (4), WNV has spread throughout much of Africa (5,6), Europe (7), West Asia (8), Oceania (9), and the Americas (10,11). The enzootic cycle is maintained between birds (the reservoirs) and mainly mosquitoes (the vectors), whereas humans are accidental dead-end hosts (Figure 1). Other mammals such as horses, dogs, camels, and goats are also accidental dead-end hosts for WNV (12). The role of animal monitoring in the surveillance of WNV outbreaks is critical because detecting the virus in animals can help to anticipate its transmission to humans. Moreover, domestic animals such as horses (13) and poultry ( 14) have been used as sentinels for human cases. Furthermore, wild birds such as crows have been used to define the geographic and temporal limits of WNV in North America (15).Because WNV does not produce specific clinical symptoms, WNV infection can be mistaken for other infectious diseases and toxins ( 16). WNV outbreaks can easily be attributed to other arbovirus diseases that are more common and result in greater human illness in an area. For this reason, any evidence regarding the presence of WNV in an area is important to ensure monitoring of the risk for humans contracting the disease caused by WNV. Thus, all WNV reports should serve as suitable input data for pathogeographic analyses (17) aimed at mapping the areas at risk for WNV transmission to humans.We conducted a bibliographic review of the detection of WNV in animals in Africa. Next, we applied biogeographic methods to create empirical models on the basis of the virus lifecycle to identify zones that are environmentally favorable for the circulation of WNV in Africa. Moreover, the models were used to ascertain the potential risk for transmission of WNV to animals (epizootic processes) and humans (epidemic processes), even in regions where WNV has not yet been detected. Materials and Methods Data Sources and Search StrategyWe performed a literature search in the GIDEON database (18) for 48 countries and territories of Africa (Figure 2), using "West Nile fever" and country names as keywords. For countries that had name changes since 1937, when WNV was first described, we also searched for the ancient names or names that they were otherwise known by; for example, Equatorial Guinea (formerly Spanish Guinea), Saharawi Arab Democratic Republic (Western Sahara), and Côte d'Ivoire (Ivory Coast). We excluded the island countries and territories of Africa from this analysis because WNV probably would be enzootic and independent of the annual movements of migratory birds. The size and isolation of some of these island countries and territories would deserve an independent approach to study WNV (19). We complemented

Screening of Circulation of Usutu and West Nile Viruses: A One Health Approach in Humans, Domestic Animals and Mosquitoes in Burkina Faso, West Africa

“…This monitoring is mainly concerned with DENV, YFV, zika and chikungunya viruses, with no analysis of USUV or WNV having been performed thus far. Notably, a modeling study has identified a number of countries (Togo and Benin) bordering Burkina Faso as areas at risk of the emergence of WNV [ 12 ].…”

“…To date, USUV infection has been reported in a dozen European countries, with more than a hundred cases of acute human infection being described, mainly in Europe [ 2 , 11 ]. Contrary to USUV, WNV has been described as responsible for many epidemics in Africa, Europe, and the United States [ 12 ]. On the African continent, cases of WNV have been reported in the Democratic Republic of Congo, Gabon, Namibia, and Tunisia [ 13 ].…”

Next-generation sequencing survey of acute febrile illness in Senegal (2020–2022)

“…Our phylogenetic analysis of the three detected strains demonstrates that WNV circulation within Senegal is affected by transmission chains involving both European and North American nations ( Figure 4 ). While the importance of North American-to-African transmission of WNV is unclear and requires further study, the repeated observations of transmission between Europe and Africa can be explained by yearly bird migrations on the Mediterranean-Sahel flyway ( Hahn et al, 2009 ; Najdenski et al, 2018 ; García-Carrasco et al, 2022 ). Our maximum-likelihood molecular clock phylogeny and accompanying discrete phylogeographic analysis ( Figure 4 , bottom right) also revealed the relatedness of the WNV strains found in Bounkiling with at least 39 strains recently causing a neuroinvasive outbreak in northern Italy ( Barzon et al, 2022a , b ).…”

Epidemiological Analyses of the First Incursion of the Epizootic Hemorrhagic Disease Virus Serotype 8 in Tunisia, 2021–2022

“…Ecological niche modeling (ENM) can be used to predict the abundance and the spread of VBDs [ 33 ] which in turn could be useful for planners in creating mosquito/VBD surveillance programs. A commonly used method to buildspecies distribution models (SDMs)in the ecological niche theory framework includes regression-based methods, such asgeneralized linear models (GLMs).This algorithm has widely proven to produce robust models for predicting species distribution [ 34 , 35 , 36 , 37 , 38 ] as well as for infectious diseases [ 39 , 40 ]. In this study, we elaborated distribution models (through GLMs) in order to: (1) establish the potential area of distribution of the potential vector in Tunisia, (2) to define the potential area of EHDV distribution cases.…”