Molecular characterization of chikungunya virus during the 2019 outbreak in the Democratic Republic of the Congo

Abstract

Early 2019, a chikungunya virus (CHIKV) outbreak hit the Democratic Republic of the Congo (DRC). Though seldomly deadly, this mosquito-borne disease presents as an acute febrile (poly)arthralgia often followed by long-term sequelae. Although Aedes aegypti is the primary vector, an amino acid substitution in the viral envelope gene E1 (A226V) is causing concern as it results in increased transmission by Aedes albopictus, a mosquito with a much wider geographical distribution. Between January and March 2019, we collected human and mosquito samples in Kinshasa and Kongo Central province (Kasangulu and Matadi). Of the patients that were tested within 7 days of symptom onset, 49.7% (87/175) were RT-qPCR positive, while in the mosquito samples CHIKV was found in 1/2 pools in Kinshasa, 5/6 pools in Kasangulu, and 8/26 pools in Matadi. Phylogenetic analysis on whole-genome sequences showed that the circulating strain formed a monophyletic group within the ECSA2 lineage and harboured the A226V mutation. Our sequences did not cluster with sequences from previously reported outbreaks in the DRC nor with other known A226V-containing ECSA2 strains. This indicates a scenario of convergent evolution where A226V was acquired independently in response to a similar selection pressure for transmission by Ae. albopictus. This is in line with our entomological data where we detected Ae. albopictus more frequently than Ae. aegypti in two out of three affected areas. In conclusion, our findings suggest that CHIKV is adapting to the increased presence of Aedes albopictus in DRC.

First observation of Aedes albopictus in the Tshuapa province (Boende) of the Democratic Republic of the Congo

“…albopictus also exist in other cities located near the Congo River or its tributaries throughout the Congo Basin. If this is the case, we predict that the frequency and magnitude of Aedes -borne viral outbreaks will increase significantly the following years across Central DRC, similar to what we currently observe in South-Western DRC 10 .…”

“…albopictus in Africa was reported four decades ago (Nigeria), its presence in the Democratic Republic of Congo (DRC) was only described for the first time in 2018 9 . One year later, we linked a major CHIKV outbreak to its recent colonization in that area (the provinces Kinshasa and Kongo Central during 2019-2020) 10,11 . Indeed, Ae.…”

“…Furthermore, we could link the CHIKV outbreak to an amino acid substitution in the viral envelope gene E1 (E1-A226V) which makes the virus more suitable for dissemination by Ae. albopictus 10 . These previous results indicate that Ae.…”

High Aedes spp. larval indices in Kinshasa, Democratic Republic of Congo

“…In several epidemics, Ae. albopictus has been shown to be the main driver of transmission for the chikungunya virus, especially the one of the ECSA lineage with the A226A, as shown in a recent outbreak in Kinshasa [41].…”

High Aedes spp. larval indices in Kinshasa, Democratic Republic of Congo

“…albopictus, which is an exotic species for Africa, might change the epidemiology for a number of arboviruses in Africa. Considered as a secondary vector for dengue virus, it can drive transmission of the chikungunya virus, especially the one of the ECSA lineage with the A226A, as shown in Kinshasa in the recent outbreak [40].…”