Some risk factors, for example asthma or high blood pressure, may make you more likely to be infected or to become severely ill. When you visit your doctor or go to a hospital, information on your medical conditions is recorded. Approved researchers can access this information. We will use this information to learn more about which factors may make you more likely to have an infection in winter, and to become severely ill because of this infection. We also want to learn about which risk factors are linked with just one infection and which are linked with multiple infections. Knowing this will enable doctors and other health care professionals to take extra care of people at risk. This should mean that they are less likely to need to see a doctor or go to hospital and may reduce pressures on the national health service.