Inclusion Criteria:  Age 16 years or over Admitted to an adult, general ICU in England or Wales as an emergency (unplanned) Admitted to ICU for either: a) confirmed COVID-19 between 1st January to 1st July 2020 or b) without confirmed COVID-19 between 1st July 2016 and 1st July 2020-  Exclusion Criteria:  Patients who died in hospital after treatment on an ICU