Inference and control of the nosocomial transmission of methicillin-resistant Staphylococcus aureus

Pei, Sen; Morone, Flaviano; Liljeros, Fredrik; Makse, Hernán; Shaman, Jeffrey L

We performed an analysis of the admission and discharge traffic in the study hospitals. In the hospitals, the inpatient population changed on a daily basis. To quantify the speed of patient renewal, we define a patient overlap ratio at day t as QðtÞ ¼ jZðt À 1Þ \ ZðtÞj=jZðt À 1Þj, where ZðtÞ is the set of patients in the hospital at day t, and jZðtÞj is the number of those patients. In Figure 1 -figure supplement 2A, we present the evolution of QðtÞ during a period of 300 days. QðtÞ exhibits a somewhat periodic behavior with a period of 7 days (see the inset of Figure 1-figure supplement 2A) . This is possibly due to reduced patient traffic during weekends. We next examined the total number of patients in the study hospitals. As shown in Figure 1 -figure supplement 2B, the in-hospital patient number fluctuates between 4000 and 7000. Patient numbers exhibit a periodic behavior at an annual time-scale, as well as at finer weekly time-scale. We also present the number of new patients (with respect to the patients present the previous day) in the hospitals each day in Figure 1 -figure supplement 2B. The number of new patients is relatively small compared with the total patients.