Epidemics

Epidemics are outbreaks of contagious diseases (1)___ an unusually large number of people or involving an extensive geographical area. Epidemics, which may be short-lived or last for years, are brought on by the widening reach of disease-causing organisms. These organisms can be (2)___ by food or water, directly from one person to another through (3)___ contact, or by the exchange of bodily secretions such as saliva, semen, or (4)___. Insects, rodents, and other disease-carrying animals, are agents that may (5)___ human populations with epidemic diseases.

Among the diseases that have occurred in epidemic proportions throughout history are bubonic (6)___, influenza, smallpox, typhoid (7)___, tuberculosis, cholera, bacterial meningitis, and diphtheria. Occasionally, childhood (8)___ such as mumps and German measles become epidemics.

In the past, when sanitary conditions were (9)___ and diseases were little understood, epidemics occurred periodically and killed thousands of people. One of the largest epidemics ever recorded was the (10)___ of bubonic plague that raged throughout Europe, Africa, and Asia from 1347 to 1350. This epidemic, known as the Black Death in Europe, is estimated to have killed one-third of the European population. An outbreak of influenza in 1918 killed more than 20 million people around the world. Such global epidemics are commonly called (11)___. Wars and foreign invasions have traditionally provided breeding grounds for epidemic disease. Prior to the 20th century, every European war produced more (12)___ from disease than from the use of weaponry. Colonists arriving in the western hemisphere carried disease-causing organisms to which they were immune but that devastated the populations of Native Americans who had no previous exposure to these organisms. Due to the spread of disease the population of central Mexico (13)___ by an estimated 90 percent in the first 50 years of Spanish domination.

Epidemics can often be (14)___ or controlled by immunization, improved sanitation, and by other public (15)___ measures such as the use of pesticides to wipe out disease-carrying insects. During the 1960s and 1970s, the medical profession hoped that epidemic diseases were well on their way to (16)___. Poliomyelitis, an (17)___ viral disease of the central nervous system that had once been a scourge of young people in the United States, no longer appeared in significant numbers, and other diseases, including smallpox, tuberculosis, malaria, and cholera seemed almost neutralized. But since the 1970s, 30 new disease-causing (18)___, including acquired immunodeficiency syndrome (AIDS), Ebola hemorrhagic fever, and hepatitis C, have been identified, most of them emerging from new settlements in the rain forests of South America, Africa, and Asia. New antibiotic-resistant strains of influenza, tuberculosis, meningitis, cholera, and malaria have also appeared.

Fortunately, disease (19)___ and control establishments are now in place through most of the world and have repeatedly shown themselves capable of responding quickly and (20)___ to sudden outbreaks of disease.