Answer:
infectious agent
Step-by-step explanation:
Chickenpox is a contagious disease caused by the Varicella-Zoster virus.
For a person to be infected with this virus, an infection transmission chain needs to occur. This chain is formed by three links: host, infectious agent and environment.
The environment represents the appropriate place for the infectious agent to reach a healthy individual. The infectious agent is the parasite that causes the disease and the host is the infected person.
In this case, we can say that chicken pox represents the infectious agent, since it is caused by the Varicella-Zoster virus.