Table 1 Case definitions
Term | Acronym | Classification | Explanation | |
|---|---|---|---|---|
Surveillance | Hospital-onset, hospital-acquired case | HOHA | An individual hospitalised with COVID-19 with symptom onset after a defined cut-off of days from admission and prior to discharge | An individual identified with COVID-19 in a hospital that was presumed to be infected with SARS-CoV-2 in the hospital |
Surveillance | Community-onset, community-acquired case | COCA | A hospitalised COVID-19 case with a symptom onset before a defined cut-off of days from admission and prior to discharge | An individual with identified COVID-19 in the hospital or community that was presumed to be infected with SARS-CoV-2 in the community |
Surveillance | Cut-off days for definition of hospital-acquired infection (in identified cases) | 7 days (4 or 14 used in sensitivity analysis) | If symptoms onset occurs after this number of days from admission but before discharge then the case is identified as hospital-acquired | |
To be estimated | Unidentified hospital-acquired infection | “Missed” | A person infected with SARS-CoV-2 during a hospital stay but not identified as symptom onset was after the patient was discharged | Our model estimates how many patients with hospital-acquired infections would be unidentified by using a definition of hospital-acquired that relies on symptom onset prior to discharge. We do not consider asymptomatic infections. We did not consider community-acquired infections “misclassified” as hospital-acquired as the percentage is very small after only a few days from admission (Additional file 3, see HOCA below) |
“Misclassified” | A person infected with SARS-CoV-2 during a hospital stay but not identified as symptom onset was before the defined cut-off | |||
To be estimated | Total number of patients with hospital-acquired infections | A person infected with SARS-CoV-2 during a hospital stay | The combined total of identified (those with symptom onset after a defined cutoff) and unidentified infections (“missed” and “missclassified”) | |
To be estimated | Community-onset, hospital-acquired case | COHA | A hospitalised community-onset COVID-19 case that has a community-acquired classification but was actually a unidentified hospital-acquired infection | Our model prediction of how many unidentified hospital-acquired infections would return as a hospitalised COVID-19 case. These need to be re-classified as hospital- not community-acquired |
To be estimated | Community-onset, hospital-linked case | COHL | A hospitalised community-onset COVID-19 case that was infected in a chain of four generations of transmission that started with an unidentified hospital-acquired infection | Our model prediction of the contribution of unidentified hospital infections to onward community transmission approximately 1 month after discharge |
Minimal | Hospital-onset, community-acquired case | HOCA | Symptoms after the cutoff for defining hospital-acquired, but infection was in the community | We estimate that less than 1% of those with symptom onset more than 5 days from admission would have a community-acquired infection (Additional file 3) |