A child is seen in a health care clinic, and a diagnosis of chickenpox is confirmed. The mother expresses concern for two other children at home and asks the nurse if the child is infectious to the other children. Which response by the nurse is most appropriate?

1. "The infectious period occurs after the lesions begin."

2. "The infectious period begins with the onset of the rash."

3. "The infectious period is not known, and it is possible that the children may develop the chickenpox within the next 2 weeks."

4. "The infectious period begins 1 to 2 days before the onset of the rash and ends about 5 days after the onset of the lesions and crusting of the lesions."