In many countries for many years health care workers have become infected with HIV as a result of their work. The main cause of infection in occupational settings is exposure to HIV-infected blood via a percutaneous injury (i.e. from needles, instruments, bites which break the skin, etc.). The average risk for HIV transmission after such exposure to infected blood is low - about 3 per 1,000 injuries. Nevertheless, this is still understandably an area of considerable concern for many health care workers. The original source is at http://www.avert.org/needlestick.htm.