In the 1300’s a form of the bubonic plague called the “Black Death,” one of the worst epidemics known to man, killed a fourth of the population in Europe. Millions died in a short period of time. The plague was transmitted to human beings chiefly by fleas from infected rats. An epidemic in a seaport was especially dangerous because rats traveled first class from country to country on ships and trains. So rat control is disease control. The term “dirty rotten rat” should not be considered an insult as much as a medical term.