Martin Heymann, age 14, of Creswell, Ore., for his question:

WHAT IS BUBONIC PLAGUE?

Bubonic plague is a    highly contagious disease that has killed millions of people over the centuries. In fact, during the 1300s a form of bubonic plague spread throughout Europe, claiming a quarter of the population its victims. Often called the Black Death, the disease is caused by a germ transmitted to humans by fleas from infected rats. Besides spots of blackish blood appearing under the skin, there are usually swellings in the lymph glands, called buboes, from which the disease is named.

Modern methods of sanitation and pest control have helped diminish the severity and widespread destruction of bubonic plague. A vaccine to increase resistance to the disease can be given, but it is not entirely effective. A victim can be treated with certain antibiotics and, of course, is isolated to reduce the chances of someone else catching it.