Well, time to pay attention once more—live virus cancer therapy is back. In a recent preliminary report from San Diego, a small group of patients with advanced liver cancer received doses of vaccinia virus, the same virus injected for more than 200 years to prevent smallpox. Patients were given either a high or low dose; those receiving the larger amount lived significantly longer, suggesting that perhaps the vaccinia was beneficial.

Viruses other than vaccinia are being examined as well, including herpes and adenovirus; the latter is a common cause of gastroenteritis and of pinkeye. Despite the extremely high-tech nature of the work, little is understood regarding how a virus kills a cancer cell. Some attack it directly. Others require scientific manipulation, which involves splicing in a bit of genetic material that is then delivered to a cancer cell, making it more susceptible to subsequent chemotherapy or radiation. Still others viruses are engineered to trigger a more pronounced inflammatory response from the patient’s own immune system.