Returning ex-patriot Chinese to Guangdong, China, increase the risk for local transmission of Zika virus.

Objectives: Fast expansion and linkage to microcephaly and Guillain Barre syndrome have made Zika virus (ZIKV) track attention of global health authority concerns. The epidemiology, virological characteristics and genetic evolution of introduced ZIKV to Guangdong, China, were investigated.

Methods: Analyses of the epidemiological characteristics and genetic diversity of ZIKV isolates were performed.

Results: A total of twenty-eight confirmed ZIKV infection cases were imported into China in 2016, of which 19 were imported into Guangdong, China from Venezuela (16), the Samoa Islands (1), Suriname (1) and Guatemala (1). Serial sampling studies of the cases indicated longer shedding times of ZIKV particles from urine and saliva samples than from serum and conjunctiva swab samples. Seven ZIKV strains were successfully isolated from serum, urine and conjunctiva swab samples using cell culture and neonatal mouse injection methods. Genomic analysis indicated that all viruses belonged to the Asian lineage but had different evolutionary transmission routes with different geographic origins. The molecular clock phylogenetic analysis of the ZIKV genomes indicated independent local transmission that appeared to have been previously established in Venezuela and Samoa. Additionally, we found 7 unique non-synonymous mutations in the genomes of ZIKV that were imported to China. The mutations may indicate that ZIKV has undergone independent evolutionary history not caused by sudden adaptation to Chinese hosts.

Conclusion: The increasing number of ex-patriot Chinese returning from ZIKV hyper-endemic areas to Guangdong combined with the presence of a variety of Aedes species indicate the potential for autochthonous transmission of ZIKV in Guangdong.