Diphtheria is a highly contagious and potentially fatal infection that can affect the nose, throat and sometimes the skin. Although rare in the UK due to routine childhood vaccinations, there's a small risk of catching it while travelling in some parts of the world. Diphtheria is highly contagious. It's spread by coughs and sneezes, or through close contact with someone who's infected. Diphtheria antibodies are produced by the body following a diphtheria infection.