More on Zika virus here
Enveloped, spherical, about 50 nm in diameter. The surface proteins are arranged in an icosahedral-like symmetry. Mature virions contain two virus-encoded membrane proteins (M and E), while immature virions contain a membrane protein precursor.
Source: Zhang et al(Pubmed)
Monopartite, linear, ssRNA(+) genome of of 10-11 kb. The genome 5’ end has a methylated nucleotide cap for canonical cellular translation. The 3’ terminus is not polyadenylated but forms a loop structure. This secondary structure leads to the formation of a subgenomic flavivirus RNA (sfRNA) through genomic RNA degradation by host XRN1. sfRNA is essential for pathogenicity, and may play a role in inhibiting host RIG-I antiviral activity as shown for Dengue virus
The virion RNA is infectious and serves as both the genome and the viral messenger RNA. The whole genome is translated in a polyprotein, which is processed co- and post-translationally by host and viral proteases.
- Attachement of the viral envelope protein E to host receptors mediates internalization into the host cell by clathrin-mediated endocytosis, or by apoptotic mimicry
- Fusion of virus membrane with host endosomal membrane. RNA genome is released into the cytoplasm.
- The positive-sense genomic ssRNA is translated into a polyprotein, which is cleaved into all structural and non structural proteins (to yield the replication proteins).
- Replication takes place at the surface of endoplasmic reticulum in cytoplasmic viral factories. A dsRNA genome is synthesized from the genomic ssRNA(+).
- The dsRNA genome is transcribed/replicated thereby providing viral mRNAs/new ssRNA(+) genomes.
- Virus assembly occurs at the endoplasmic reticulum. The virion buds via the host ESCRT complexes at the endoplasmic reticulum, is transported to the Golgi apparatus.
- The prM protein is cleaved in the Golgi, thereby maturing the virion which is fusion competent.
- Release of new virions by exocytosis.