Zika virus is an enveloped, positive-sense single-stranded RNA virus in the genus Flavivirus. It is transmitted mainly by Aedes aegypti and Aedes albopictus mosquitoes and causes Zika fever, a generally mild illness that can lead to congenital anomalies when infection occurs during pregnancy.
Genome and Virology
The Zika virus genome is a positive-sense RNA molecule approximately 10.8 kilobases in length. It encodes a single open reading frame translated into a polyprotein that is co- and post-translationally cleaved into three structural proteins (capsid, premembrane/membrane and envelope) and seven nonstructural proteins (NS1, NS2A, NS2B, NS3, NS4A, NS4B and NS5). The envelope protein mediates attachment to host cell receptors such as AXL and TYRO3 on human neural progenitor cells and DC‑SIGN on dendritic cells. Entry occurs via clathrin-mediated endocytosis; low pH in endosomes triggers fusion and release of the genome. Replication takes place on modified endoplasmic reticulum membranes, with the NS5 RNA-dependent RNA polymerase synthesising negative-strand intermediates and new genomes, and NS3 serving as a helicase and protease. Zika virus replicates in a wide range of cell types, including skin fibroblasts, neural stem cells, placental trophoblasts and male reproductive tract epithelial cells. Virions assemble on the endoplasmic reticulum, mature in the Golgi and are released by exocytosis. Genetic lineages include African and Asian/American; the Asian lineage was responsible for recent epidemics and exhibits mutations that may enhance neurotropism.
Epidemiology and Associated Disorders
First identified in 1947 in Uganda, Zika virus circulated silently in Africa and Asia for decades. Large outbreaks occurred in 2007 on Yap Island, Micronesia, and in French Polynesia in 2013. A major epidemic spread across the Americas in 2015‑2016, infecting millions and revealing previously unrecognised complications. Most infections are asymptomatic or produce mild fever, rash, conjunctivitis, arthralgia and myalgia. However, infection during pregnancy can cause congenital Zika syndrome, characterised by microcephaly, cerebral calcifications, eye abnormalities and other developmental defects. Zika virus infection is also linked to Guillain–Barré syndrome and other neurologic complications in adults. Transmission occurs primarily through mosquito bites but can also occur vertically, sexually and via blood transfusion. There is no approved antiviral therapy or vaccine; prevention focuses on mosquito control, personal protection measures and delaying pregnancy in areas of active transmission. Surveillance and vector management remain critical to reduce outbreaks and protect vulnerable populations. Zika virus emerged from obscurity to become a significant public health concern due to its ability to cause congenital abnormalities and neurologic disease. Understanding its replication, tissue tropism and epidemiology is essential for developing vaccines and targeted interventions. Related Terms: West Nile Virus, Dengue Virus, Yellow Fever Virus, Chikungunya Virus, Aedes aegypti