TropicalMed, Vol. 7, Pages 420: Analysis of a Dengue Virus Outbreak in Rosso, Senegal 2021

Dengue fever is caused by one of four dengue virus (DENV) serotypes, namely DENV1-4 [1]. The virus belongs to the Flaviviridae family and flavivirus genus and is known to be present in many tropical and subtropical areas around the world [2]. Due to associated morbidity and mortality, the virus is one of the major public health threats in these areas [3]. Infection with the dengue virus causes clinical manifestations ranging from malaria-like symptoms (dengue fever) to life-threatening diseases (Severe dengue) [4]. According to the World Health Organization (WHO), 390 million people are infected by dengue each year [5]. Cases range between 50 to 100 million each year, with a fatality rate of 1–5% [6,7]. The virus epidemiology is relatively well-known in most American and Asian countries, but in contrast, little is known for the African continent, where the virus has circulated since the 19th century [8,9]. The lack of information about the dengue virus in Africa is probably linked to low awareness of the virus, the absence of effective surveillance, the presence of other pathogens causing similar clinical manifestations (malaria and bacterial infections) and the lack of diagnostic tools [9]. Dengue outbreaks associated with distinct serotypes have been reported from Zanzibar, Burkina Faso, Mauritania, Djibouti, Mozambique, Mauritania, Cote d’Ivoire, and Senegal [10,11]. Overall, all known dengue virus serotypes have been detected in Africa [12]. In Senegal, the first dengue case was reported in 1970 in the Bandia area located in the Thies region [13]. Since then, many outbreaks and sporadic cases [14,15,16] have been reported periodically. Until 1999, the landscape of dengue virus circulation was dominated by the circulation of sylvatic DENV-2 in southern Senegal [17]. In 2009, a major change was noticed with the first circulation of DENV-3 in West Africa, causing a large urban outbreak affecting Dakar, Louga and Thies [15]. In 2015, a study on arboviral etiologies of Non-Malarial febrile illnesses (NMFI) using a portable laboratory based on Recombinase Polymerase Amplification (RPA) detected three dengue cases serotype 1 in the suburb of Dakar [18]. Between 2017–2018, unprecedented multifocal and multiserotype circulations of dengue virus were noticed in Senegal, affecting mainly regions such as Louga (2017; Co-circulation DENV1-2), Thies (2018; Co-circulation DENV1-3), Fatick (2018; Co-circulation DENV1 and DENV-3), Touba (2018; circulation DENV-3), Rosso (2017; circulation DENV-2) [16]. Overall, past studies reveal growing evidence of dengue hyperendemicity in Senegal [19,20]. For virus detection, several PCR assays are available [21,22,23]. NS1 antigenic detection was shown to be useful in previous studies [24]; however, in Africa, RDTs test has not been commonly used for dengue diagnosis despite their performance and easy deployment at the point of need [24,25].

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