Epidemiology of dengue fever in Gabon: Results from a health facility-based fever surveillance in Lambaréné and its surroundings

Abstract

Background In Africa, information on dengue is limited to outbreak reports and focused on some countries with continuing transmission in West and East Africa. To estimate the proportion of dengue-positive cases among febrile patients and identify clinical indicators of dengue cases, we conducted passive facility-based fever surveillance in a catchment area population of 70,000 residents of Lambaréné and its surroundings in Gabon. Methods Non-malarial febrile patients with current fever or history of fever (≤7 days) between 1 and 55 years of age, were enrolled at Albert Schweitzer Hospital (ASH). Acute (visit 1, day of enrollment) and convalescent blood samples were collected between 10 and 21 days after enrollment. Acute/convalescent samples were tested with IgM/IgG ELISA, and a selected subset of acute samples with RT-PCR. Results Among 682 non-malarial febrile patients enrolled, 119 (17.4%) were identified as dengue-positive (94 dengue-confirmed and 25 dengue-probable cases). Of these dengue-positive cases, 14 were confirmed with PCR, and based on serotyping, two infections were identified to be DENV-2 and two were DENV-3. The majority of our enrolled patients were <25 years of age and close to 80% of our dengue-positive cases were <15 years of age. In adjusted analyses, retro-orbital pain and abdominal pain were 2.7 and 1.6 times more frequently found among dengue-positive cases, compared to non-dengue cases. Conclusion Lambaréné is not considered dengue-endemic. However, one in six non-malarial febrile episodes was found to be dengue-positive in the study period. Dengue should be considered more frequently in clinicians’ diagnosis among non-malarial febrile patients in Lambaréné. Given the lack of data on dengue in Gabon, additional prospective and longitudinal studies would help to further define the burden and patterns of dengue for improved case detection.

Seroepidemiological Study of Dengue Virus Infection Suspected Cases in Burkina Faso

“…The present study found that 19.4% of dengue suspected cases were positive for at least one of three serological markers of dengue fever (NS1Ag, IgM and IgG) from 2017 to 2020 in Ouagadougou. Our data agrees with the reports of Lim JK et al, 2021 in Lambaréné in Gabon who found a prevalence of 17.4% [24]. Before the 2016 outbreak, dengue was a neglected disease in Burkina Faso.…”

Re-emergence of dengue, chikungunya, and Zika viruses in 2021 after a 10-year gap in Gabon

“…The phylogenetic tree also showed that the clade of the Gabonese strains was separated from that of the Angola/2013 strain, suggesting that DENV-1 has circulated persistently in Gabon since its last appearance. Considering previous reports from 2015‒2017 showing the detection of both DENV-2 and 3 in the same area ( Abe et al., 2020 ; Lim et al., 2021 ), the serotype has likely now switched to DENV-1. The emergence of severe dengue cases should be carefully monitored in the area because secondary infections by other serotypes increase the risk of developing severe dengue ( Vaughn et al., 2000 ).…”

“…Recent examples were outbreaks of chikungunya in the Democratic Republic of the Congo in 2019 and dengue in Burkina Faso in 2017. Sporadic molecular and serological surveys have been conducted on DENV, CHIKV, and ZIKV in Gabon since the first documentation of the outbreaks or occurrence of infectious diseases caused by DENV-2, CHIKV, and ZIKV in 2007 ( Leroy et al., 2009 ; Grard et al., 2014 ; Abe et al., 2020 ; Lim et al., 2021 ; Ushijima et al., 2021 ). However, little information is available on the genetic diversity and spatiotemporal dynamics of these viruses.…”

Arboviruses as an unappreciated cause of non-malarial acute febrile illness in the Dschang Health District of western Cameroon

“…As demonstrated by our study, ARBV such as DENV are important causes of fever, but attack rates can vary broadly from season to season or between relatively small distances. For example, 17.4% of 682 non-malaria febrile cases in a large health facility in Gabon were diagnosed as DENV, [ 18 ] and in Madagascar, DENV was the most common cause of AFI in one recent study. [ 55 ] Local epidemiology determines pre-test probability of a given diagnosis, which affects clinical decision making.…”

“…There is currently no report of routine DENV diagnosis and treatment in health systems in Africa despite evidence of continuous, ongoing DENV transmission in East and West Africa, [1,15,16] and more recently in central Africa. [17][18][19] Consequently, febrile children and adults are managed as presumptive cases of malaria or bacterial infections, which limits the attention and awareness for infections caused by DENV or other viruses. Indeed, over treatment of malaria in Africa is well documented.…”