Colds and flu are viral infections that are spread through coughing, sneezing and personal contact. Colds are caused by over one hundred different viruses, including rhinoviruses, corona viruses and adenoviruses. Influenza is caused by influenza viruses, including types A, B and C.
Children, older people and those with depleted immune systems (e.g. due to illness or ongoing stress) are more likely to catch colds and flu than others and may experience more severe bouts of infection.