A 21-year-old man presents with symptoms of headache, fever, chills, and discomfort in both sides of his jaw. He has also noticed discomfort in his testes, but no dysuria or urethral discharge. Physical examination reveals bilateral enlargement of the parotid glands, as well as bilateral testicular enlargement and tenderness on palpation. His temperature is 38.5degC pulse rate of 92/min, and the remaining examination is normal. Laboratory data show hemoglobin 15 g/dL; hematocrit 40%; WBC 12000/mL, with 30% segmented neutrophils, 8% monocytes, and 62% lymphocytes. Which of the following statements concerning this disease is true?