Answer:
Incubation period
Step-by-step explanation:
The incubation period is the time period between the entry of pathogen into the host body and the appearance of signs and symptoms. Chickenpox is caused by varicella-zoster virus that has an incubation period of 10-23 days after which the symptoms of the disease appear.
The virus must have spread from the infected nephew two weeks ago but did not cause any sickness until now due to the incubation period.