In many parts of the world injections are the preferred treatment for many illnesses. The act of injecting something into the body is a potent symbol of medicine and patients or their mothers, will often demand an injection and go to someone who will give it, for consultations without treatment are not paid. But injections require needles and syringes which are expensive and, like the medicines which are injected, must also be sterile. If they are re-used they must be properly cleaned and sterilised. In one study, needles had been reused twenty five times, but each syringe was reused for over seven hundred patients. As the needle is withdrawn, small amounts of blood are drawn in and if the patient is infected with HIV or hepatitis virus, the next person may be infected. Drug users draw blood into the syringe to rinse out any left over drug before re-injecting. Especially in prisons where syringes are forbidden, this habit leads to epidemics of HIV infections. Doctors and nurses, forgetting their training, may reuse needles and syringes.