Staphlococcus Aureus is found on the skin or in the nose of around 20-40% the population and seems to cause them no problems. They are said to be colonised or carriers. However, it can become a problem if the individual becomes run down, has wounds, undergoes surgery, has catheters or has intravenous drips as this allows the bacteria to enter the body.
Therefore MRSA is more commonly found in hospitals where patients are at a greater risk of infection. MRSA is unlikely to harm healthy people, but it can cause serious infection and even death in vulnerable individuals.