Its host range is largely limited to human cells. Although a relation between varicella and herpes zoster has been recognized since the late 19th century, the identity of these isolates was not established until the advent of in vitro culture techniques in the 1950s and molecular biology technology in the 1980s. More than 90 percent of cases involve children younger than nine years, and most adults have antibody to the virus.
Infection is spread by respiratory droplets or by direct contact with active lesions.
Fomites are not an important mode of transmission. Chicken pox occurs most frequently in the winter and the spring and spreads rapidly to susceptible household members. The incubation period ranges from 11 to 20 days. Herpes zoster results from the reactivation of VZV infection. There is no seasonal pattern for herpes zoster.