When are patients with mumps infectious relative to parotid swelling?

• A. Only during the parotid swelling
• B. 7 days after the onset
• C. 48 hours prior to and 9 days after onset
• D. 2 weeks before the onset

Answer: (C)

Mumps is contagious through respiratory droplets and saliva, and the virus is shed before symptoms appear. The infectious period begins about two days before parotid swelling starts and lasts roughly nine days after the onset of swelling. So if swelling begins on day zero, the patient is contagious from day minus two to day plus nine. This window explains why transmission can occur before swelling is evident and why precautions are needed before and after the appearance of parotitis.