Final answer:
The varicella-zoster virus causes chickenpox on initial infection and can reactivate to cause shingles later in life.
Step-by-step explanation:
The varicella-zoster virus is a double-stranded DNA virus that causes chickenpox during the initial infection. Postinfection, the virus becomes dormant within nerve-cell ganglia but can be reactivated later in life, causing shingles, a disease characterized by a painful, localized rash, often on one side of the body.
However, one cannot develop shingles without first having chickenpox, as shingles results from the reactivation of the varicella-zoster virus that has entered into a dormant state after a previous chickenpox infection.
Regarding the virus's double-stranded DNA, it provides an evolutionary advantage in that it can integrate into the host DNA more efficiently than single-stranded DNA, perhaps contributing to its ability to establish latency and potential for reactivation.