Millions of operations are carried out in the NHS every year. Infection is a rare but important complication that can happen after surgery. Specific operations are routinely monitored every year in every NHS hospital to see how often these post-surgery infections occur. This is very time-consuming as it is done in person by an infection control nurse for 3 months every year in every hospital, and continuously in cardiac surgery. Even then, the nurses are only able to follow-up patients whilst they are in hospital, and cannot find out if patients get infections after they have been discharged. Every time a person comes to hospital or has an operation, a large amount of routine electronic data is recorded, including about the operation (what type it was, how long it went on for), what blood tests were done and what was found, how long people stayed in different wards for etc. In this project we want to try to use this data to see if we can accurately and reliably predict who developed post-surgery infections, using the data collected by hand by the nurse as the “gold standard”. If we can do this, we could monitor these infections throughout the year.