Prevention is characterised by activities that are taken to reduce the possibility that something will happen, or to minimise harm if it does occur. The prevention of illness or disability requires the identification of the factors that contribute to poor health and modifying, reducing or eliminating them, or, conversely, building and strengthening protective factors. Prevention is usually taken as a core responsibility of organised health systems-alongside the curative, restorative and palliative functions-and is a key element in achieving health improvement and the reduction of the burden of disease in society. Prevention is also an important component of many other branches of social policy (for example crime prevention, child abuse prevention), many of which also contribute, directly or indirectly, to health.