Malaria in Senegal is due essentially to infections by Plasmodium falciparum and, to a lesser extent to Plasmodium malariae and Plasmodium ovale. By the use of molecular methods, detection of Plasmodium vivax has been recently reported in the region of Kedougou, raising the question of appraisal of its potential prevalence in this setting. A retrospective serological study was carried out using 188 samples taken from 2010 to 2011 in a longitudinal school survey during which 48 asymptomatic children (9–11 years) were recruited. Four collections of samples collected during two successive dry and rainy seasons were analysed for antibody responses to P. vivax and P. falciparum. Recombinant P. falciparum and P. vivax MSP1 antigens and total P. falciparum schizont lysate from African 07/03 strain (adapted to culture) were used for ELISA. Nested PCR amplification was used for molecular detection of P. vivax. A surprising high prevalence of IgG responses against P. vivax MSP1 was evidenced with 53% of positive samples and 58% of the individuals that were found positive to this antigen. There was 77% of responders to P. falciparum outlined by 63% of positive samples. Prevalence of responders did not differ as function of seasons. Levels of antibodies to P. falciparum fluctuated with significant increasing between dry and rainy season (P < 0.05), contrary to responses to P. vivax. There was a significant reciprocal relationship (P < 10−3) between antibody responses to the different antigens, but with weak coefficient of correlation (Rho around 0.3) underlining a variable profile at the individual level. Clear molecular signature was found in positive IgG to P. vivax msp1 samples by PCR. This cross-sectional longitudinal study highlights the unexpected high circulation of P. vivax in this endemic area. Sero-immunology and molecular methods are powerful additive tools to identify endemic sites where relevant control measures have to be settled and monitored.

In Senegal, the burden of dengue is increasing and expanding. As case management and traditional diagnostic techniques can be difficult to implement, rapid diagnostic tests (RDTs) deployed at point of care are ideal for investigating active outbreaks. The aim of this study was to evaluate the diagnostic performance of the Dengue NS1 and Dengue IgM/IgG RDTs on the serum/plasma samples in a laboratory setting and in the field. During laboratory evaluation, performance of the NS1 RDT was assessed using NS1 ELISA as the gold standard. Sensitivity and specificity were 88% [75–95%] and 100% [97–100%], respectively. Performance of the IgM/IG RDT was assessed using the IgM Antibody Capture (MAC) ELISA, indirect IgG, and PRNT as gold standards. The IgM and IgG test lines respectively displayed sensitivities of 94% [83–99%] and 70% [59–79%] and specificities of 91% [84–95%] and 91% [79–98%]. In the field, the Dengue NS1 RDT sensitivity and specificity was 82% [60–95%] and 75% [53–90%], respectively. The IgM and IgG test lines displayed sensitivities of 86% [42–100%] and 78% [64–88%], specificities of 85% [76–92%] and 55% [36–73%], respectively. These results demonstrate that RDTs are ideal for use in a context of high prevalence or outbreak setting and can be implemented in the absence of a confirmatory test for acute and convalescent patients.

West Nile virus (WNV), belonging to the Flaviviridae family, causes a mosquito-borne disease and shows great genetic diversity, with at least eight different lineages. The Koutango lineage of WNV (WN-KOUTV), mostly associated with ticks and rodents in the wild, is exclusively present in Africa and shows evidence of infection in humans and high virulence in mice. In 2016, in a context of Rift Valley fever (RVF) outbreak in Niger, mosquitoes, biting midges and sandflies were collected for arbovirus isolation using cell culture, immunofluorescence and RT-PCR assays. Whole genome sequencing and in vivo replication studies using mice were later conducted on positive samples. The WN-KOUTV strain was detected in a sandfly pool. The sequence analyses and replication studies confirmed that this strain belonged to the WN-KOUTV lineage and caused 100% mortality of mice. Further studies should be done to assess what genetic traits of WN-KOUTV influence this very high virulence in mice. In addition, given the risk of WN-KOUTV to infect humans, the possibility of multiple vectors as well as birds as reservoirs of WNV, to spread the virus beyond Africa, and the increasing threats of flavivirus infections in the world, it is important to understand the potential of WN-KOUTV to emerge.

Crimean-Congo hemorrhagic fever (CCHF) is a zoonosis transmitted mainly by ticks. In Senegal, the CCHF virus has been circulating since at least 2003. However, the first symptomatic human case was detected and confirmed only in 2023 in the southeastern part of the country. Following this detection, a survey of humans, animals and ticks was launched to better characterize the ecology of this virus in this area. Human samples were tested by ELISA and RT-PCR. Serum and tick samples collected from cattle, sheep and goats were tested by ELISA and by RT-PCR, respectively. Antibodies against CCHFV were detected in 0.77 % of humans and 14.18 % of animal sera. The highest seroprevalence was observed in cattle (58.3 %), followed by goats (33.33 %) and sheep (8.33 %). The tick infestation rate was higher in cattle (8.2 %) than in sheep (1.2 %), while goats were not infested. Hyalomma rufipes was the first tick found infected in southeastern Senegal with a CCHF viral minimum field infection rate of 13.3 %. Thus, this study enabled us to better understand the mechanisms of CCHFV emergence in southeastern Senegal.

The COVID-19 pandemic required massive testing of potential patients in resource-constrained areas in Senegal. The first case of COVID-19 was reported on 2 March 2020 in Dakar city and on 10 March, the first cases were reported in Touba city, the second most populous city in Senegal. Following the scale of confirmed COVID-19 cases in Touba city, the Institut Pasteur de Dakar mobile laboratory truck (MLT) was deployed on March 13 to bring diagnostics to the point of need for better management of patient and outbreak control. The MLT deployed is a 6 × 6 truck equipped with an isolator for sample inactivation, a generator and batteries to ensure energy autonomy, and a molecular platform for pathogens detection. Nasal and oropharyngeal swabs were collected from suspected COVID-19 cases and sent to the MLT located at the Touba primary healthcare center. Samples were extracted and RNA amplified by real time qRT-PCR. A total of 11,693 samples were collected from 14 regions of Senegal and tested between March to August 2021. Within the samples tested, 10.6% (1240/1693) were positive for SARS-CoV-2. Furthermore, the MLT allowed the confirmation of the first cases of COVID-19 in 25 out of 79 health districts of Senegal. Thereby, the MLT deployment during the first 6 months of COVID-19 in Senegal allowed rapid processing of suspected case samples collected in Touba and other surrounding areas and, thus, significantly contributed to the outbreak response and early case management in Senegal.

: Hepatitis E, caused by hepatitis E virus (HEV), is a highly endemic disease with a major public health impact. In Senegal, the first HEV outbreak was identified in 2014 in Kedougou, and a recent study focusing on pregnant women showed a seroprevalence of 7.8%. Apart from these data, very little is known about its burden in Senegal, and there is no specific surveillance program. We describe HEV prevalence among acute febrile jaundice patients in Senegal. A retrospective analysis using jaundice samples (2008–2020) collected through the national yellow fever surveillance program were tested for HEV by IgM/IgG ELISA and reverse transcription polymerase chain reaction (RT-PCR). Sequencing and phylogenetic analyses were performed on RT-PCR-positive samples. Statistical tools were used to analyze the HEV prevalence. In total, 2,387 samples were tested, and 174 IgG, 135 IgM/IgG, and 29 IgM positive samples were detected. Among the IgM-positive samples, 74 were positive by RT-PCR. The results showed an overall HEV prevalence of 14% in febrile jaundice patients in Senegal. Phylogenetic analyses showed the circulation of genotype 2b. Our data confirmed the HEV outbreak in Kedougou in 2014 and showed the detection of acute cases in other regions. We also detected in these regions genotype 2b, which is usually associated with large outbreaks in many African countries, suggesting a high risk of HEV outbreak occurrence in Senegal. Finally, our data showed that the yellow fever surveillance program, which is based on jaundice and already exists in many countries, could be a valuable tool for HEV surveillance.