Problem: Mattias, Trevia, and Laura all work in a large metropolitan city when a life-threatening infectious disease begins to break out in three different pockets around the city. Mattias is sent to the homes of the individuals first identified as having the disease. He interviews family members and friends and counsels those who need to be screened. While visiting each household, he asks about places the first patient went and who he or she came in contact with and how. Then he retraces that patient's step and contacts other individuals who may have been exposed. Finally, as time progresses, he and his fellow nurses divide up the cases that ultimately result in infection to continually follow up with each individual, offering counseling and referrals as needed.