Which virus is primarily responsible for the symptoms of chickenpox?

The virus primarily responsible for the symptoms of chickenpox is the Varicella-zoster virus (VZV). This virus is a member of the herpesvirus family and is specifically known for causing chickenpox during the primary infection. Following the initial infection, which typically manifests with an itchy rash and flu-like symptoms, the virus can remain dormant in the sensory nerve ganglia. Later in life, VZV can reactivate and cause shingles (herpes zoster), which is characterized by painful rashes localized to certain dermatomes.

The other viruses listed do not cause chickenpox: the herpes simplex virus primarily causes oral and genital herpes, Epstein-Barr virus is responsible for mononucleosis and is linked to certain cancers, and cytomegalovirus is often associated with congenital infections and can cause illness in immunocompromised individuals but is not related to chickenpox symptoms. Therefore, Varicella-zoster virus is the definitive answer for chickenpox.