Concurrent Circulation of Dengue Serotype 1, 2 and 3 among Acute Febrile Patients in Cameroon

Dengue is the most prevalent mosquito-borne arboviral disease throughout the tropics and sub-tropics globally. Long considered to be scarce in Africa, dengue has been on the rise on the continent in the past two decades. Yet little is known of dengue epidemiology and even the range of active serotypes is unknown in many countries, including Cameroon. As part of ongoing studies on arbovirus epidemiology in Cameroon, we investigated the contribution of dengue infections to the burden of acute febrile illness recorded in public hospitals Between July to December 2020, volunteers over three years of age presenting with acute febrile illness of less that 7 days duration were recruited in four hospitals in Douala. Dengue infections were detected, and serotype determined using real time RT-PCR to target a fragment of the 5’ and 3’ UTR genomic regions. The envelope gene of dengue positive samples was amplified by RT-PCR, sequenced, and phylogenetic trees were inferred for genotype identification. In total, 12.8% (41/320) of the acute febrile patients in four public hospitals in Douala were positive to dengue virus. Dengue virus 3 (DENV-3) was the most common serotype found (68.3%), followed by DENV-2 (19.5%) and DENV-1 (4.9%), 14.6% of the sample could not be serotyped. Co-infections of DENV-3 and DENV-2 were found in 3 cases. This is the first description ever of the simultaneous occurrence of three dengue serotypes in Cameroon. Infections were more prevalent in adults (78.38%) than in children below 15 years old (21,62%). Jaundice and headache were the most frequent clinical signs associated with infection and 23 cases (55%) were co-infections with malaria. Phylogenetic analysis of the envelope gene identified DENV-1 as belonging to genotype V, DENV-2 to genotype II and DENV-3 to genotype III. The simultaneous occurrence of three serotypes in Douala reveals dengue as a serious public health threat for Cameroon and highlights the need for further epidemiological studies and dengue outbreak prevention and response plans in the major cities of this region