Zika Virus

About Zika Virus Zika virus (ZIKV) is an enveloped, positive-sense single-stranded RNA virus in the genus Orthoflavivirus and family Flaviviridae. It is transmitted primarily by infected Aedes mosquitoes, although sexual, congenital, and blood-associated transmission can also occur. Many ZIKV infections are asymptomatic or cause a mild illness characterized by fever, rash, conjunctivitis, arthralgia, myalgia, and headache. Infection during pregnancy can result in congenital Zika syndrome, including microcephaly and other fetal abnormalities, and infection has also been associated with neurologic complications such as Guillain-Barré syndrome. Mature ZIKV particles are approximately 50 nm in diameter and contain a host-derived lipid envelope surrounding a nucleocapsid. The envelope protein E forms the major surface layer, mediates receptor interaction and low-pH membrane fusion, and is the principal target of neutralizing antibodies. Membrane protein M is generated by cleavage of the precursor prM during virion maturation.

After receptor-mediated uptake, acidification of the endosome triggers rearrangement of E protein and fusion of the viral and cellular membranes. The genomic RNA is released into the cytoplasm, translated as one polyprotein, and processed into structural and nonstructural proteins. Replication occurs on rearranged endoplasmic-reticulum membranes, followed by assembly, maturation through the secretory pathway, and release of new virions.

The ZIKV genome is approximately 10.8 kb and contains a 5′ untranslated region, a single long open reading frame, and a 3′ untranslated region without a poly(A) tail. The genome carries a type I cap at the 5′ end and is translated into one polyprotein that is cleaved by host proteases and the viral NS2B-NS3 protease.

The amino-terminal portion of the polyprotein produces the three structural proteins C, prM/M, and E. The remaining region produces seven nonstructural proteins that coordinate polyprotein processing, membrane remodeling, genome replication, virion assembly, and modulation of host responses.