Space-fill drawing of the outside of one Zika virus particle, and a cross-section through another as it interacts with a cell. By David Goodsell [CC BY 4.0 (https://creativecommons.org/licenses/by/4.0)]For the past 65 years, the Zika virus has regularly circulated throughout Africa and Southeast Asia, resulting in mild, sporadic cases. It wasn’t until the 2015 – 2016 Zika epidemic in the Americas that researchers shifted their attention to this flavivirus, which was linked to an increase in reported birth defects and neurological disorders. These increasing Zika cases prompted researchers to investigate the evolution of the Zika pathogen, which they discovered was driven by increased human exposure to wild pathogen reservoirs. These elevated human-pathogen interactions are a result of (1) expanding deforestation and agriculture, (2) the globalization and urbanization of human populations, and (3) the adaptation of the pathogen’s vector host, the mosquito (Ae. aegypti), to spread more effectively. When they investigated this geographical expansion of the Zika-harboring mosquito, they found that the Zika virus had differentiated into two distinct lineages; the African lineage and the Asian/American lineage. Based on previous evidence, Zika infections in Africa were variable and tended to result in mild symptoms such as fever or skin rash, unlike the recently emerged Asian-lineage Zika infections in the Pacific Island and Americas, which have resulted in severe birth defects such as microcephaly. In an effort to characterize the differences between the two viral lineages, CEID member Courtney Murdock and colleagues compared replication, ability to cause disease, and transmission efficiency between these Zika isolates in a variety of different environments. They cultured the two lineages in cell cultures, within the mosquito host, and within an embryo model to see if genetic variation resulted in observable differences in characteristics. While their study did not address specific mechanisms behind the genetic variation, their results provide broad, informative information regarding the genetic differences between the Zika lineages under a variation of laboratory models. Their results are crucial for understanding the evolution of the Zika virus and how to combat the dynamics of this pathogen system to reduce its threat to global health.
Willard, Katherine, et al. “Zika Virus Exhibits Lineage-Specific Phenotypes in Cell Culture, in Aedes Aegypti Mosquitoes, and in an Embryo Model.” Viruses, vol. 9, no. 12, 2017, p. 383., doi:10.3390/v9120383.
