Focus: Students complete a short "surprising statistics" quiz on the impact of infectious diseases, then classify several diseases as "emerging," "re-emerging," or "endemic."
Major Concepts: Infectious diseases continue to be a major cause of human suffering and death, both in the United States and around the world. Emerging infectious diseases are diseases that have not occurred in humans before or that occurred only in small numbers in isolated places. Re-emerging infectious diseases are diseases that once were major health problems globally or in a particular country, and then declined dramatically, but are again becoming health problems for a significant proportion of the population.
Objectives: After completing this activity, students will
Prerequisite Knowledge: Students should be familiar with bacteria and viruses and understand that infectious diseases are due to infection of the body by an external agent.
Basic Science-Public Health Connection: This opening activity introduces emerging and re-emerging infectious diseases as a public health issue that can be examined using the methods of science (for example, collecting and organizing data into categories).
In developing countries where much of the population lives in conditions of extreme poverty, infectious diseases remain the leading cause of death. In the United States, prevention and control of infectious diseases have been so successful in the past half century that many people view infectious diseases as either a thing of the past or minor illnesses easily treated and cured, except among the very young, very old, or seriously ill.
In recent years, however, Americans have been shocked by the emergence of a variety of "new" infectious diseases. For example, Escherichia coli strain 0157:H7 caused severe vomiting and diarrhea among patrons of Jack in the Box restaurants in Washington State in 1993 and among children swimming in public pools in Atlanta, Georgia, in 1998. And a previously unrecognized virus (a hantavirus) caused a frequently fatal respiratory illness among apparently healthy young people in the Southwest. New diseases have emerged in developing countries as well. Ebola hemorrhagic fever, which was first described in 1976 in Zaire (now the Democratic Republic of the Congo), has particularly horrifying symptoms and a fatality rate of 50 to 90 percent. And AIDS, which emerged simultaneously in the United States and Africa in the early 1980s, has become a global pandemic.
Likewise, many diseases thought to be adequately controlled appear to be making a "comeback." In developed countries, public health measures such as sanitation, sewage treatment, vaccination programs, and access to good medical care including a wide range of antibiotics have virtually eliminated "traditional" diseases such as diphtheria, whooping cough, and tuberculosis. However, many of these diseases are becoming a public health problem once again, as immunization programs and other public health standards are enforced less vigorously and, especially, as antibiotic-resistant pathogens evolve. In fact, medical workers have identified strains of pneumonia-causing Staphylococcus aureus that are resistant to all of the currently available drug treatments, and physicians and public health workers are concerned that we are about to re-enter the preantibiotic era for treating such diseases. Among the diseases "re-emerging" as a consequence of microbial resistance are tuberculosis and malaria, leading causes of death from infectious diseases worldwide.
This activity engages students in the seriousness of infectious diseases by helping them become aware of the widespread impact of such diseases. Students discover that some diseases are relatively new to humankind (emerging diseases), while others that had been nearly eliminated in developed countries are now beginning to increase in incidence (re-emerging diseases). They also learn that many diseases have been a perennial problem in human populations, never significantly declining (endemic diseases).
You will need to prepare the following materials before conducting this activity:
To make the disease cards, copy Master 1.2 and cut the copy apart to form individual cards. Glue each card to a 5 . 7 index card.
Note to teachers: Activity 3 includes a bacterial growth experiment. If you are teaching the activities on consecutive days, students will need to complete Steps 5 to 8 on Master 3.1a, Bacterial Growth Experiment, during this class session. See Master 3.1a for details.
1. Introduce the module and this activity by asking students, "What disease do you think is the greatest threat to students in this class? What disease do you think is the greatest threat to the world's population?" Solicit several responses and entertain a brief discussion about the diseases students perceive as threats and why.
List students' responses on the board or a transparency.
Heart disease was the top killer globally in 1998. AIDS and cancer are likely to be two of the top threats students perceive. According to the World Health Organization (WHO), in 1998 AIDS was the fourth highest killer worldwide, while cancer of the trachea, bronchus, or lung was the ninth highest killer. Also in the top 10 killers globally were cerebrovascular disease (second), pneumonia (third), chronic obstructive pulmonary disease (fifth), diarrheal diseases such as cholera (sixth), perinatal conditions (seventh), tuberculosis (eighth), and traffic accidents (tenth).
2. Tell students that, as a class, they will take a quiz on some past and current causes of death and illness. Explain that you do not expect them to know the answers to these questions, but ask them to make well-reasoned guesses based on what they do know. Then display a transparency of Master 1.1, Causes of Death Quiz, solicit students' answers to each item, and provide the correct answers.
If you have the equipment to project the video Infectious Disease Then and Now on the Web site for the whole class, you can substitute this video for the quiz. The video covers roughly the same content and may take less time than the quiz. Both the quiz and the video serve an Engage role for this activity and the module.
Question 1 Which of the following diseases has been recognized since antiquity?
(c) Guinea worm disease, or dracunculiasis, is mentioned in biblical texts. Although it is unfamiliar to Americans, it is not uncommon on the Arabian peninsula and sub-Saharan Africa. The disease is caused by a parasitic roundworm that is ingested in a larval form. The larvae migrate through the tissues where they mate and grow. A year after they are ingested, the mature female migrates to subcutaneous regions, typically in the legs and feet. The worm may reach a yard in length. Its migrations cause great pain and inflammation, a burning itch, and subcutaneous ulcers. One form of treatment is to wet the skin to stimulate the worm to stick its head out and catch the head in a split stick. The worm is then slowly extracted, over the course of several weeks, by rolling it around the stick (if it is pulled too quickly, the worm will break in two, causing greater problems). This treatment may be the origin of the caduceus symbol that represents the medical profession. Students will learn as they complete this activity that Legionnaire disease and Ebola fever were first recognized as distinct diseases in 1976, and AIDS first came to worldwide attention in the early 1980s.
Question 2 In the 1700s and 1800s, a terrible, wasting disease killed thousands of European and American city dwellers. What disease was this?
(d) Tuberculosis (TB) killed 1 of every 4 Americans in the 1800s. The disease is still a leading killer globally, although it had decreased dramatically in the United States until the AIDS epidemic. The immune system of most people who contract the bacterium that causes tuberculosis successfully prevents its growth and active disease never develops. Any condition that compromises the immune system, such as HIV infection, will allow the bacteria to grow, resulting in active tuberculosis.
Question 3 What infectious disease causing severe fever and chills plagued settlers in the Southern and Midwestern United States during the 1800s and early 1900s?
(c) Malaria is thought to have been introduced to the United States from Europe and Africa in the 16th and 17th centuries. The incidence of malaria in this country probably peaked around 1875. In a review of U.S. malaria outbreaks, J. Zucker estimated that more than 600,000 cases occurred in 1914. Improved socioeconomic conditions, mosquito control measures, and availability of effective drugs later led to the virtual elimination of this disease in the United States, although localized outbreaks are still occasionally reported.
Question 4 Most deaths among U.S. servicemen in 1918 were due to what cause?
(b) Flu caused most of these deaths. The global influenza epidemic of 1918 is estimated to have killed 30 million people. The movement of troops during World War I, accompanied by crowding, poor nutrition, and generally poor living conditions probably contributed to the rapid spread of the flu around the world. The 1918 flu was particularly virulent and, unlike typical flu epidemics, caused death more frequently among young adults than among children and the elderly.
Question 5 In 1994, a terrible disease nearly killed an 18-year-old high school student in California. Which of the following diseases was it?
(d) Tuberculosis (TB). The student contracted TB from a classmate at her high school, who had an active, misdiagnosed case of the disease. An additional 11 students at her school developed active cases of TB, and several hundred more had positive skin tests indicating that they had been exposed. The student tells her story in Activity 3, Superbugs: An Evolving Concern.
Question 6 According to the World Health Organization, which of the following diseases caused more deaths in 1998 than the others?
(d) Pneumonia was the third-highest killer in 1998, behind heart disease and cerebrovascular disease.
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