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. 2022 Oct 3;131:1–11. doi: 10.1016/j.jhin.2022.09.019

Figure 1.

Figure 1

Figure 1

Delta SARS-CoV-2 introduction and transmission between two wards. (A) Origin of SARS-CoV-2 Delta variant on Ward 1. CA, community-acquired; HA, hospital-acquired; SOD, date of core respiratory, core gastrointestinal or expanded COVID symptom onset or the date the case tested positive for COVID-19, whichever is sooner; PT, patient; HCW, healthcare worker; DSP, designated support person. Solid lines: strong epidemiological link based on work assignment, detailed interview and/or any reported personal protective equipment (PPE) breaches. Direction of arrow: direction of transmission. (B) Epidemic curve of Delta SARS-CoV-2 outbreak on two medical wards. Epidemic curve showing cases (patient and HCW) by symptom onset date (SOD). SOD is the date of core respiratory, core gastrointestinal or expanded COVID symptom onset or the date the case tested positive for COVID-19, whichever is sooner. OB, outbreak. Dates of outbreaks on Wards 1 and 2 are indicated by a green and orange line, respectively. Outbreak on Ward 2 closed on day 59 (indicated by forward-facing arrow). Black arrow indicates HCW movement between Wards 1 and 2. Open black arrows indicate key epidemiological events. (C) Introduction and transmission of Delta SARS-CoV-2 on Ward 2. SOD is the date of core respiratory, core gastrointestinal or expanded COVID symptom onset or the date the case tested positive for COVID-19, whichever is sooner. Solid lines denote transmission event with strong epidemiological link based upon work assignment, detailed interview and/or any reported PPE or hand hygiene breaches; dashed black lines denote possible transmission based upon care dates and communicable phase of illness; blue lines indicate patient-to-patient transmission event or patients who were roommates; black lines indicate HCW-to-patient transmission event; orange lines indicate patient-to-HCW transmission event; black frames around HCW cases denote shift overlap with a co-worker. Absence of any line indicates that source of infection is unknown/no specific interaction between patients and/or HCWs identified. In all cases the risk period refers to the communicable phase of illness (defined as 48 h before symptom onset until 14 days after symptom onset).