3.5 COVID-19 Outbreak definitions

The definitions below should be applied to determine if a COVID-19 outbreak within a healthcare setting is occurring and determine when it can end. When assessing patient and staff clusters to determine if an outbreak is occurring, a high degree of suspicion should be applied.

3.5.1 Criteria to declare a COVID-19 outbreak in an inpatient setting

Two or more patient or staff cases of COVID-19 within a specific setting where nosocomial infection and ongoing transmission is suspected. For the purposes of this reporting, a high degree of suspicion should be applied and should be completed for any non-COVID-19 ward where there are unexpected cases of suspected or confirmed COVID-19. e.g. any cases that were not confirmed or suspected on admission. No time limit should be applied to determining whether a case is nosocomial e.g. 48 hours.


In High Risk Pathway where two or more staff cases of suspected or confirmed COVID-19 are identified.

Note: If there is a single suspected or confirmed case in a patient who was not suspected as having COVID-19 on admission, this should initiate further investigation and risk assessment This single case may constitute a possible cluster or an outbreak depending on the contacts and exposures identified.  Where patient has been in a side room with transmission based precautions in place for 48 hours prior to symptom onset, and where all staff were wearing appropriate PPE appropriately, the IPCT may decide that there is no further action needed other than active monitoring for any new unexplained cases associated with the ward.

3.5.2 Criteria to determine that a COVID-19 outbreak in an inpatient setting has ended

No new test-confirmed or suspected cases with illness onset date 14 days following the last new confirmed case (from date of symptom onset or date of positive test if case has remained asymptomatic), within the affected ward or department.  The outbreak can be declared closed provided that these criteria are met.  Stepdown guidance and further information on isolation periods can be accessed .