Varicella-zoster virus

The varicella-zoster virus (VZV), also known as human herpesvirus 3 (HHV-3), is one of the eight herpesvirus known to affect humans (and other vertebrates). It causes chickenpox as a primary infection and rarely VZV encephalitis. It can remain dormant in the host and later reactivates to induce shingles (herpes zoster, zoster multiplex, myelitis, herpes ophthalmicus, or zoster sine herpete) and post-herpetic neuralgia.

It belongs to the genus Varicellovirus and the subfamily Alphaherpesvirinae. It is closely related to the herpes simplex viruses, sharing much genome homology. It is usually spherical and 150-200 nm in diameter. Its lipid envelope encloses the nucleocapsid of 162 capsomeres arranged in a hexagonal form. Its DNA is a single linear, double strand molecule, 125,000 nt long.

The virus is very susceptible to disinfectants, notably sodium hypochlorite. Within the body it is combatted by a number of drugs including vidarabine, zoster immune globulin (ZIG), and acyclovir. A live-virus vaccine has been approved and is sold under the name Varivax. It was developed by Merck, Sharp and Dohme in the 1970s from a virus isolated by Mishiaki Takahashi and identified as Oka. It had a series of tests in the 1980s and was offered to the FDA for approval in 1990 and was finally passed in 1995.