Final answer:
Chickenpox is caused by the varicella-zoster virus and most people acquire lifelong immunity after the first infection. However, in rare cases, the virus can reactivate years later, leading to a second episode of chickenpox. With minimal treatment or medication, the person can recover from the second episode.
Step-by-step explanation:
Chickenpox is a common childhood disease caused by the varicella-zoster virus. Once infected, most individuals acquire a lifetime immunity to future chickenpox outbreaks. However, in rare cases, as in Tracy's situation, a person may experience a second episode of chickenpox. This is possible because the virus can become dormant in the body and then reactivate many years later. In these cases, the person may recover with minimal treatment or medication.