For centuries past, plague was the scourge of the earth, killing at least an estimated 163 million people during three major worldwide pandemics. Today, plague still exists in the world although the number of cases and deaths is much lower. Plague still infects several thousand people a year and kills several hundred. Most cases are in southern Africa, Asia, and central South America.

Plague is an infectious disease that affects animals and humans. It is caused by the bacterium Yersinia pestis and is usually found in rodents and their fleas. When released into the air, the bacterium can survive for up to an hour. People usually contract the disease after being bitten by an infected flea or after handling an infected animal. To reduce the risk of death, antibiotics must be given within 24 hours after the first symptoms occur.

There are three types of plague and they can occur...