Coxsackie A virus (CAV) is a cytolytic Coxsackievirus of the Picornaviridae family, an enterovirus (a group containing the polioviruses, coxsackieviruses, and echoviruses). Viral structure and genome Coxsackie A virus is a subgroup of enterovirus A, which are small, non-enveloped, positive-sense, single-stranded RNA viruses. Its protective, icosahedral capsid has an external portion that contains sixty copies of viral proteins (VP1,-2,-3) and an internal portion surrounding the RNA genome containing sixty copies of VP4 viral proteins. This capsid mediates cell entry and elicits the humoral immune responses. Enteroviruses have a depression encircling each fivefold axis (canyon), which is their binding site for immunoglobulin-like receptors. This binding can trigger viral expansion and release of its genome. A complete genome analysis of Coxsackie virus A2, A4, A5, and A10 strains isolated from individuals with hand-foot-mouth disease showed that natural recombination is frequent in the virus's evolution. Its strains in China were related to strains in Mongolia, Taiwan, likely to those that circulated in Europe, and form a distinct lineage from strains imported from Japan and South Korea. Replication cycle Replication of the coxsackie virus happens through contributions of the host and virus components. The virus enters the cell where it is internalized into endoplasmic reticulum and the Golgi apparatus. After viral un-coating, viral RNA is released. Ribosomes on the rough endoplasmic reticulum translate the RNA into viral polyprotein. This polyprotein is processed into structural protein P1 and non-structural proteins P2 and P3. Via the virus-encoded proteinase, P1 is processed into the viral capsid subunit proteins VP0, -1, -3. The 5'-non-coding region contains sequences that control genome replication and translation, while the 3'-non-coding region contains polyA tail needed for virus infectivity. Diseases The most well known Coxsackie A disease is hand, foot and mouth disease (unrelated to foot-and-mouth disease), a common childhood illness which affects mostly children aged 5 or under, often produced by Coxsackie A16. In most individuals, infection is asymptomatic or causes only mild symptoms. In others, infection produces short-lived (7–10 days) fever and painful blisters in the mouth (a condition known as herpangina), on the palms and fingers of the hand, or on the soles of the feet. There can also be blisters in the throat, or on or above the tonsils. Adults can also be affected. The rash, which can appear several days after high temperature and painful sore throat, can be itchy and painful, especially on the hands/fingers and bottom