Chikungunya and Zika Virus Cases Detected against a Backdrop of Endemic Dengue Transmission in Vietnam

Abstract

Between 2010 and 2014, four chikungunya and two Zika virus infections were identified among 8,105 febrile children in southern Vietnam. Zika viruses were linked to French Polynesian strains, chikungunya to Cambodian strains. Against a backdrop of endemic dengue transmission, chikungunya and Zika present an additional arboviral disease burden in Vietnam.

Figure 1.

Residential location of the study patients and study hospitals. Locations of the chikungunya and Zika cases are shown with black circles and stars, respectively; hospitals are shown as black crosses. Two chikungunya cases were located approximately 20 km from the border with Cambodia.

Figure 2.

Maximum likelihood phylogenies of chikungunya and Zika virus. (A) Maximum likelihood phylogeny of the E1 gene of the chikungunya virus East/Central/South African (ECSA) Indian Ocean Outbreak lineage. The tree was constructed in IQ-TREE (TNe + Γ₄, 1,000 bootstraps) using a 1,743-nt alignment of a representative subsample of Indian Ocean Lineage (IOL) viruses, with Angola 1962 (HM045823) as an outgroup. Vietnamese isolates are indicated by closed black circles. Cambodian sequences are shown with open circles. (B) Maximum likelihood phylogeny of the E gene of the Zika virus Asian genotype. The tree was constructed in IQ-TREE (Vienna, Austria; TN + Γ₄, 1,000 bootstraps) using a 1,512-nt alignment of a representative subsample of Asian genotype viruses, with Malaysia 1966 (KX694533) as an outgroup. Vietnamese isolates from this study (2013) are indicated by closed black squares. The Vietnamese isolate from 2016 is indicated by an open square. Bootstrap values are shown for nodes with bootstrap support ≥ 70%. Scale bars represent the number of nucleotide substitutions per site.