- Close contacts of patients are evaluated twice a week for 2 weeks, then once a week for 2 more weeks. Blood is drawn at the first visit and then at 1, 2, and 4 weeks. Mouth and throat swabs, nose washings, and sputum collections are done twice a week for 2 weeks, then once a week for 2 more weeks. Urine and stool samples are collected once a week for 4 weeks. If virus from the nose or throat is still detectable after 4 weeks, weekly nose washings and throat swabs continue until no virus is detected for 3 weeks in a row. Blood may also be drawn during the weekly visits.