Low Circulation of Zika Virus, Cambodia, 2007-2016

Abstract

We describe a retrospective study on circulation of Zika virus in Cambodia during 2007-2016 among patients with dengue-like symptoms and Aedes aegypti mosquitoes. Our findings suggest that Zika virus in Cambodia belongs to the Asia genotype, is endemic, has low prevalence, and has had low-level impact on public health.

Keywords: Cambodia; Flaviviridae; Zika virus; circulation; diagnosis; flavivirus; infection; vector-borne infections; viruses.

Figure 1

Phylogenetic tree of Zika virus partial nonstructural protein 5 gene of 3 strains detected from humans in Cambodia. The partial sequences of the nonstructural protein 5 gene (192–194 nt) generated from the PCR products obtained for each strain were analyzed and assembled by using CLC Main Workbench 5.5 package (CLC bio A/S, Aarhus, Denmark). MEGA6 (14) was used to perform multiple sequence alignment of Cambodia strains with Zika virus reference strains from Africa and Asia genotypes available in GenBank and phylogenetic analyses by using maximum-likelihood method using the general time reversible model with 1,000 bootstrap resampling. Spondweni virus (GenBank accession no. AF013406) was used to root the tree. Cambodia strains from this study are indicated by bold type and a black triangle, and the Cambodia strain isolated in 2010 is indicated by bold type and a white triangle. Scale bar indicates nucleotide substitutions per site.

Figure 2

Geographic distribution of Zika virus in Cambodia. PCR- and IgM-positive cases were from 9 different provinces in north, central and south Cambodia. The 5 Zika virus–positive samples by quantitative real-time reverse transcription (qRT-PCR) in this study were distributed as follows: the 2007 (n = 1) sample was received from Kampong Cham province, and the other cases from 2008 (n = 1), 2009 (n = 2), and 2015 (n = 1) were from the Phnom Penh area (red star). The first case of Zika virus infection previously reported in Cambodia by conventional RT-PCR was diagnosed in a patient from Kampong Speu province (9). The 16 additional serum samples found to be positive for Zika virus IgM were, from oldest to the most recent, from Phnom Penh (2007, n = 1; 2008, n = 1; 2010, n = 2); Battambang (2007, n = 1; 2012, n = 1); Takeo (2012, n = 1); Kampong Speu (2012, n = 1); Kampot (2012, n = 1; 2015, n = 1); Kampong Chhnang (2015, n = 1); Banteay Meanchey (2015, n = 1); and Siem Reap (2015, n = 4) provinces. Light gray indicates provinces with IgM-positive cases, dark gray indicates province with PCR-positive cases, and black indicates provinces with PCR-positive and IgM-positive cases. Inset shows location of Cambodia in Southeast Asia.