Last month's article considered the role of the law in preventing the spread of infectious disease in cases such as tuberculosis and SARS where isolation, quarantine and treatment are effective in controlling the outbreak. Other forms of infectious disease that district nurses encounter--such as hepatitis B and C and the HIV virus that are spread through contact with blood or sexual intercourse--rely far more on the infected individual to act responsibly in preventing others from being infected. This month's article considers whether those who act recklessly and put others at risk of infection should be held criminally liable and prosecuted for their actions.