Many viruses can cause a flu-like illness. There is usually a seasonal outbreak of flu (influenza) in the UK each winter. Flu-like illnesses typically cause a high temperature (fever), aches and pains in muscles and joints, a cough and various other symptoms. Most people recover fully but complications such as pneumonia can sometimes develop. Complications are sometimes serious. Every year some people die from the complications of flu. If you are at increased risk of developing complications, you should have a flu jab (be immunised against seasonal flu) each autumn.