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Lesson 2


What Causes Rare Diseases?

collage of micrographs

Explore


At a Glance

Overview

In this lesson, students assume the roles of medical officers working to protect the health of soldiers at an army post. In the course of their duties, they must consider the major causes of disease and pay special attention to infectious diseases that have the potential to spread throughout the post. One soldier becomes infected with a common bacterial species that leads to the development of a serious rare disease.

Major Concepts

Objectives

After completing this lesson, students will have


Teacher Background

Consult the following sections in Information about Rare Diseases and Scientific Inquiry:
2.0 The Impact of Genomics on Rare Diseases
3.0 Rare Infectious Diseases
4.0 Rare Diseases Caused by Environmental Toxins
5.1 Necrotizing Fasciitis
6.0 Rare Diseases as a Topic for the Middle School Classroom


In Advance

Web-Based Activities
Activity Web Component?
1 Yes
2 Yes
3 No
Photocopies, Transparencies, Equipment, and Materials
Photocopies and Transparencies
Activity 1: Causes of Disease
For Classes Using Web-Based Activity:
1 transparency and 1 copy for each pair of students of Master 2.1
For Classes Using Print-Based Activity:
1 transparency and 1 copy for each pair of students of Master 2.1
1 copy of Masters 2.2 and 2.3 for each pair of students
Activity 2: Is a Rare Disease Present?
For Classes Using Web-Based Activity:
1 copy of Master 2.7 for each pair of students
For Classes Using Print-Based Activity:
1 copy of Masters 2.4, 2.5, 2.6, and 2.7 for each pair of students (Optional: For Master 2.6, block out the photos before copying; see note on here.)
Activity 3: How Rare Is Rare?
None
Equipment and Materials
For Activities 1 and 2, Web-based versions, students will need computers with Internet access.
For Activity 3, you will need baby lima beans for each group of four students:
  • 1 small container with 9 beans and 1 bean colored red and
  • 1 large container with 99 beans and 1 bean colored red.
Preparation

Activity 1

Make photocopies and a transparency.

WWW Logo

For classes using the Web version, verify that the computer lab is reserved for your classes or that the classroom computers are set up for the activities. Refer to Using the Web Site for details about the Web site. Check that the Internet connection is working properly.

Log on to the Web Portion of Student Activities section of the site at

http://science.education.nih.gov/supplements/rarediseases/student

Select “Lesson 2: What Causes Rare Diseases?” so students can begin the activity right away.


Activity 2

Review the photos of the necrotizing fasciitis (NF) patient on Master 2.6, Medical Reference Manual: Necrotizing Fasciitis. If the photo of the late-stage infection is too graphic for your students, block it out before copying. Make photocopies.

Activity 3

Each group of four students will need

It will save time if you weigh the beans rather than count them. There are approximately 100 baby lima beans per 1.33 ounces (37.7 grams).

Procedure

Note: This is an Explore lesson. It is designed to give students a common experience they can use to begin constructing understandings about rare diseases and their causes. In this lesson, students assume the roles of medical officers at an army post. This scenario gives students a real-life context in which to consider genetics, infectious agents, and environmental exposure as the major causes of disease. The lesson focuses on the rare disease necrotizing fasciitis (NF), more commonly known as flesh-eating disease. The serious nature of this disease may be disturbing to some students. The lesson stresses that although NF is caused by a commonly encountered bacterium, the immune system normally stops the infection before it becomes dangerous. In rare cases (about 1 in 100,000 people), the bacteria elude the immune system and the infection can lead to organ failure and death. The hands-on probability activity is included to help make the rarity of the disease more understandable and thus reduce any student anxiety.


Activity 1: Causes of Disease

Estimated time: 30 minutes

1.

Explain that in this lesson, you will be concerned with this question: What causes rare diseases?

Display this question for the class. Students should recall some causes of disease from the first lesson. In Step 8, you may need to remind students that there are three general causes of disease: infectious agents, heredity (genetics), and exposure to toxins in the environment.

2.

Open the activity by explaining that students will assume the roles of medical officers who are in charge of looking after the health of soldiers at an army post. The post is where new recruits are trained.

If necessary, explain to students that an army post is where soldiers are stationed. The soldiers live and sleep in close quarters called barracks, which are like dormitories. When they are sick or injured, soldiers visit a clinic called an infirmary.

3.

Arrange the students in pairs. Explain that their task as medical officers is to examine the list of all visits to the infirmary during the previous week. They are looking for any patterns that would indicate a health concern on the post.

For example, students should be on the lookout for any clusters of illness or accidents that may represent a larger threat to the soldiers and limit the ability of the army post to meet its responsibilities.

WWW Logo

(For print version, skip to Step 4-p below.)

In classrooms using the Web version of this activity:

4a-w.

Give each student pair a copy of Master 2.1, Medical Officer Report Form. Explain that students will add information to the form by accessing medical information on the post’s Web site.

4b-w.

http://science.education.nih.gov/supplements/rarediseases/student

Students should click on “Lesson 2: What Causes Rare Diseases?” and then “Activity 1: Infirmary Visits, Week 1.”

5a-w.

Instruct students to look over the reasons that each soldier went to the infirmary and to think about the nature of the causes of the soldiers’ complaints.

Students can sort the patients by their patient number, location (the barracks they live in), and medical complaint. This step should take no more than about five minutes.

5b-w.

After students have had a chance to look over the information on the New Visits to the Infirmary, Week 1, table ask, “What are two general reasons why soldiers reported to the infirmary?”

Students may want to respond by citing specific complaints. At this point, simply direct the discussion to bring out the fact that solders reporting to the infirmary were either sick or injured.

Continue with Step 6.



In classrooms using the print version of this activity: Open book

4-p.

Give each student pair one copy each of Master 2.1, Medical Officer Report Form, and Master 2.2, Visits to the Infirmary, Week 1. Instruct students to look over the reasons that each soldier went to the infirmary and to think about the nature of the causes of the soldiers’ complaints.

This step should take no more than about five minutes.

5-p.

After students have had a chance to look over the information in Master 2.2, ask, “What are two general reasons why soldiers reported to the infirmary?”

Students may want to respond by citing specific complaints listed on the handout. At this point, simply direct the discussion to bring out the fact that solders reporting to the infirmary were either sick or injured.

6.

Acknowledge that soldiers may become injured for many different reasons. Ask, “What about sickness?” Remind the students that in Lesson 1, they came up with three general causes of disease: infectious agents, heredity (genetics), and exposure to environmental toxins. Ask, “Which of these three causes is most likely to be responsible for a health problem that can spread throughout the post?”

Students should recognize that a disease caused by an infectious agent is the most likely to spread throughout the post.

NSES Logo Content Standard C: Disease is a breakdown in structures or functions of an organism. Some diseases are the result of intrinsic failures of the system. Others are the result of damage by infection by other organisms.
Content Standard F: Natural environments may contain substances (for example, radon and lead) that are harmful to human beings.

7.

Display Master 2.1. Ask for a volunteer to summarize the reasons that soldiers came to the infirmary.

Display the responses as you list them. Guide the discussion to focus on the following:

  • Barracks A has a cluster of six soldiers complaining of sore, itchy eyes.
  • Barracks G has a cluster of six solders complaining of sore throat.
  • Barracks E has two soldiers with a skin rash.
  • Four soldiers from three different barracks have sore toes from wearing new boots.
  • One soldier has a cut on the leg.
  • One soldier complains of shortness of breath.
  • One soldier twisted his ankle.

8.

Remind students that they need to look for potential health threats to the post. Ask, “Do you see any patterns or cases that worry you?”

Students should respond that the clusters of sore, itchy eyes; sore throats; and skin rashes could each potentially spread to other soldiers on the post. Students may also mention the soldier in Barracks I who complained of shortness of breath. The other soldiers visiting the infirmary have problems that probably won’t spread.

9.

Mention that it is possible that one or more types of infectious disease may be present on the post. Ask, “How can we tell whether or not a soldier has a bacterial infection?”

Students’ responses will vary. They may mention other symptoms such as mucous discharge or running a fever. If not mentioned by a student, turn the discussion to laboratory tests. Students may first think of a blood test. Explain that doctors can obtain a swab from a patient’s throat or other part of the body and test it for the presence of infectious bacteria.

10.

Explain that as medical officers, they have the ability to test for the presence of different species of bacteria that had previously infected soldiers on the post. Two different tests can be ordered:

  • Test 1: Looks for infection by bacterial species A, B, and C. These species are associated with common infections for pinkeye and sore throats as well as infections resulting from cuts and abrasions.
  • Test 2: Looks for bacterial infections associated with skin rashes caused by Rocky Mountain spotted fever or Lyme disease. Test 2 also looks for exposure to poison ivy (not caused by bacteria).
Note: While it is true that medical tests sometimes look for multiple causes at the same time, the tests described in this activity were created to make the test-ordering procedure easy for students to carry out.
WWW Logo

(For print version, skip to Step 11-p.)

In classrooms using the Web version of this activity:

11-w.

Instruct students to return to the Web site in their pairs and select the lab tests (if any) to perform on the soldiers. After making their selections, students should summarize on Master 2.1 which tests they ordered, which soldiers were tested, and why they ordered each test. Conduct a brief discussion to reach a consensus about which tests (if any) should be ordered and for whom.

Since the exact causes of the soldiers’ illnesses are not known, students should decide to test the solders with eye redness and sore throats with Test 1, which looks for infection by bacterial species A, B, and C.

Soldiers with skin rashes should be tested using Test 2, which looks for infection by the bacteria associated with Rocky Mountain spotted fever and Lyme disease as well as exposure to poison ivy. Students may decide not to perform tests on the soldiers complaining of sore toes. Explain that such foot blisters can become infected and suggest that they, too, be tested for possible infection using Test 1 (infection by bacterial species A, B, and C).

Some students may want to play it safe and order both tests for each soldier. Make it clear that tests come with costs, and the infirmary must perform efficiently. Therefore, only needed tests should be ordered.

Note: Pinkeye (conjunctivitis) can either be contagious or not. The contagious form of the disease is caused by a bacterial or a viral infection. A number of different bacterial species can cause a pinkeye infection.

12-w.

Instruct student pairs to return to the Web site and click on “Activity 1: Lab Test Results.”

The table that appears contains the same information about soldiers visiting the infirmary that is in “Activity 1: Infirmary Visits, Week 1.” It also lists which lab tests were ordered, the lab test results, the patient diagnosis, and the patient treatment.

13-w.

Instruct students to briefly summarize in their notebooks those cases with the potential to spread throughout the army post. Also ask them to describe how the cases were treated.

Students need not list information about each soldier. Instead, they can describe groups of soldiers with similar complaints and test results.

End of Web-based activity.



In classrooms using the print version of this activity: Open Book

11-p.

Instruct student pairs to decide which lab tests (if any) to perform on which soldiers. Groups should summarize on Master 2.1 which tests they ordered, which soldiers were tested, and why they ordered each test. Conduct a brief discussion to reach a consensus about which tests (if any) should be ordered and for whom.

Since the exact causes of the soldiers’ illnesses are not known, students should decide to test the solders with eye redness and sore throats with Test 1, which looks for infection by bacterial species A, B, and C.

Soldiers with skin rashes should be tested using Test 2, which looks for infection by the bacteria associated with Rocky Mountain spotted fever and Lyme disease as well as exposure to poison ivy. Students may decide not to perform tests on the soldiers complaining of sore toes. Explain that such foot blisters can become infected and suggest that they, too, be tested for possible infection using Test 1 (infection by bacterial species A, B, and C).

Some students may want to play it safe and order all tests for each soldier. Make it clear that tests come with costs, and the infirmary must perform efficiently. Therefore, only needed tests should be ordered.

Note: Pinkeye (conjunctivitis) can either be contagious or not. The contagious form of the disease is caused by a bacterial or a viral infection. A number of different bacterial species can cause a pinkeye infection.

12-p.

Give each student pair one copy of Master 2.3, Test Results, Week 1.

This handout contains the same information about soldiers visiting the infirmary that was found on Master 2.2. It also lists which lab tests were ordered, the lab test results, the patient diagnosis, and the patient treatment.

13-p.

Instruct students to briefly summarize in their notebooks those cases with the potential to spread throughout the army post and to describe how they were treated.

Students need not list information about each soldier. Instead, they can describe groups of soldiers with similar complaints and test results.


Activity 2: Is a Rare Disease Present?

Estimated time: 40 minutes

WWW Logo

(For print version, skip to Step 1-p.)

In classrooms using the Web version of this activity:

Note: In Step 9 of this activity, students access a medical reference manual that contains two images of a patient with flesh-eating disease. One of the images is rather graphic and may be disturbing to some students. We recommend that you view the images before class and decide whether you want students to see them. If you decide not to let students see them, instead of using the Web site for this step, give each student pair one copy of Master 2.6, Medical Reference Manual, on which you have blocked out the photos.

1-w.

Keep the students in pairs. Explain that one week has gone by, and you are ready to discuss the patient outcomes from that week. You are also going to present a list of new visits to the post’s infirmary.

2-w.

Instruct students to proceed to

http://science.education.nih.gov/supplements/rarediseases/student

Students should click on “Lesson 2: What Causes Rare Diseases?” and then “Activity 2: Follow-up on Week 1 Visits.”

After students have had a chance to look over the information in the table, ask for volunteers to summarize what they learned about the treatment outcomes of the Week 1 infirmary visits.

The cases of pinkeye, sore throat, skin rash, and asthma have responded (or are responding) to treatment. Cases of sore toes and injuries were treated, but it is too soon to describe outcomes.

3-w.

Ask, “Did you learn anything that causes you to be concerned?”

Many students will probably note that the treatments are working and will, therefore, express no particular concerns. Some students may be concerned that two of the six soldiers being treated for sore throats returned to the infirmary. Others may note that three of the four soldiers who developed blisters on their feet tested positive for infection by bacterial species A.

4-w.

Instruct students to click on “Activity 2: Infirmary Visits, Week 2.” As before, instruct students to reflect on the information and summarize in their notebooks the soldiers’ reasons for coming to the infirmary.

This step should take no more than about five minutes.

Continue with Step 5.



In classrooms using the print version of the activity: Open book

Note: In Step 9-p, student pairs get a copy of Master 2.6, which contains two images of a patient with flesh-eating disease. One of the images is rather graphic and may be disturbing to some students. We recommend that you view the images before class and decide whether you want students to see them. If not, block out the images on Master 2.6 before making copies.

1-p.

Keep the students in their pairs. Explain that one week has gone by and you are ready to discuss the patient outcomes from that week. You are also going to present a list of new visits to the post’s infirmary.

2-p.

Give each student pair one copy of Master 2.4, Follow-up on Week 1 Infirmary Visits.

3-p.

After groups have had a chance to look over Master 2.4, ask, “Did you learn anything that causes you to be concerned?”

Many students will probably note that the treatments are working and will, therefore, express no particular concerns. Some students may be concerned that two of the six soldiers being treated for sore throat returned to the infirmary. Others may note that three of the four soldiers who developed blisters on their feet tested positive for infection by bacterial species A.

4-p.

Give each pair one copy of Master 2.5, Visits to the Infirmary, Week 2. As before, instruct students to reflect on the information on the handout and to summarize, in their notebooks, the soldiers’ reasons for coming to the infirmary.

This step should take no more than about five minutes.

5.

Ask for volunteers to summarize the information they recorded in their notebooks.

Display students’ responses as you list them. Guide the discussion to focus on the following:

Some soldiers who visited the infirmary during Week 1 returned.

  • Two soldiers from Barracks G who reported to the infirmary during the first week complaining of sore throat returned with similar complaints.
  • One of the soldiers with a sore toe has developed a severe infection from bacterial species A.

Most soldiers who visited the infirmary were first-time patients.

  • Four soldiers from Barracks G appeared complaining of sore throat.
  • Two soldiers from Barracks A appeared complaining of sore throat.
  • Two soldiers (from Barracks B and F) appeared complaining of skin rashes.
  • One soldier appeared with a cut on the head.
  • One soldier appeared with an injured ankle.
  • One soldier appeared with a sore toe.

6.

Remind students that you are concerned about infectious diseases that might spread to the rest of the post. Ask, “Is there any evidence of a bacterial infection spreading throughout the post?”

Students may observe that the infection with bacterial species C that caused the pinkeye is under control and not cause for concern. They should also observe that new cases of infection by bacterial species A are sending soldiers from other barracks to the infirmary with sore throats. Some will likely report that this is a cause for concern. Finally, some students may note that bacterial species A is also responsible for a severe foot infection in one soldier who developed a blister from wearing new boots.

7.

Explain that you are concerned about the foot infection that has quickly become serious. Observe that bacterial species A seems to be responsible for two different diseases: the inflammation of the throat seen in many soldiers and the severe foot infection in one soldier. Ask, “Can the same bacterial species be responsible for causing two different diseases?”

Students will probably not be able to give a knowledgeable answer to this question. Guide the discussion to bring out the possibility that the same bacteria infecting different parts of the body might produce different symptoms.

8.

Acknowledge that it is difficult to know whether bacterial species A can cause two very different-looking diseases. Explain that the severe foot infection could be due to flesh-eating disease, which is very rare though very serious. Suggest that some research may help discover whether there is a possible link between bacterial species A and flesh-eating disease. Explain that students can look up flesh-eating disease in the Medical Reference Manual, which has a section on microbiology and disease.

NSES logo

Content Standard A: Scientific explanations emphasize evidence, have logically consistent arguments, and use scientific principles, models, and theories.

WWW Logo

9-w.

Give each pair one copy of Master 2.7, Questions about a Rare Disease. Instruct students to read the information about flesh-eating disease in the Medical Reference Manual and use it to answer the questions on Master 2.7. (To get to the Web version of the manual, students should follow Step 2-w above but click on “Activity 2: Medical Reference Manual.”)

Give students about 10 minutes to complete the tasks.



In classrooms using the print version of the activity: Open book

9-p.

Give each pair one copy of Master 2.6, Medical Reference Manual: Necrotizing Fasciitis, and Master 2.7, Questions about a Rare Disease. Instruct students to read Master 2.6 and use it to answer the questions on Master 2.7.

Give students about 10 minutes to complete the tasks.

Check mark

Students’ answers to the questions will help you assess how well they can use multiple forms of evidence to support a scientific explanation.

10.

After students have completed the tasks, ask for volunteers to report answers to each question on Master 2.7.

Answer key for Master 2.7, Questions about a Rare Disease
  1. What evidence suggests that bacterial species A causes both sore throat and foot infection?
    • Bacterial species A was cultured from throat swabs of soldiers with sore throats and from toe swabs of three out of four soldiers who developed blisters from wearing new boots.
    • The Medical Reference Manual mentions that flesh-eating disease can be caused by different species of bacteria, including the one that causes strep throat.
  2. What evidence suggests that the soldier with the foot infection has flesh-eating disease?
    • A toe swab tested positive for bacterial species A.
    • The symptoms (redness, swelling, and nausea) are consistent with flesh-eating disease, as is the timeline (symptoms progressing quickly).
  3. Why are there many cases of sore throat but only one case of flesh-eating disease?
    • Sore throats can spread among soldiers living together.
    • Flesh-eating disease generally doesn’t spread because it requires contact with an open wound.
  4. What evidence is there that flesh-eating disease is a rare disease?
    • The Medical Reference Manual states that it is rare disease. The odds of getting it are about 1 in 100,000.
    • Three soldiers with foot blisters tested positive for bacterial species A, but only one soldier developed flesh-eating disease.
  5. What should be the next step in treating the soldier with the foot infection? Explain your reasoning.
    • The soldier should be sent immediately to a hospital with the resources needed to treat flesh-eating disease. The disease is very serious. According to the Medical Reference Manual, 2 out 10 patients die from it.

Activity 3: How Rare Is Rare?

Estimated time: 30 minutes

Note: The purpose of this activity is to make the 1 in 100,000 probability of coming down with flesh-eating disease more real to the class. It is not important that the students understand how the probability calculation is performed.

1.

Observe that we all come into contact with bacterial species A and that it causes the common disease of strep throat. As this lesson shows, sometimes a bacterium associated with a common disease can also cause a rare disease. Explain that although this lesson dealt with a person who developed flesh-eating disease, the rate of this infection is actually quite low. The odds of coming down with flesh-eating disease are about 1 in 100,000.

2.

Explain that you will finish the lesson by performing a brief demonstration of the rarity of coming down with flesh-eating disease. Arrange the class in groups of four students. Give each group

  • 1 small container containing 9 baby lima beans and 1 baby lima bean that has been colored red and
  • 1 large container containing 99 baby lima beans and 1 baby lima bean that has been colored red.
NSES Logo

Content Standard A: Mathematics is important in all aspects of scientific inquiry.

3.

Display this statement: “The odds of coming down with fleshing-eating disease this year are 1 in 100,000.”

4.

Explain that you will now explore that statement. Explain that a bean colored red represents a person who may come down with flesh-eating disease. Instruct one student from each group to close his or her eyes and select 1 bean from the small container of 10 beans.

  • Ask, “Did anyone get a red bean?”

Selecting the red bean means that the student may come down with flesh-eating disease.

5.

Display this below the statement about probability: “1/10.” Explain that the odds of picking a red bean from the small container were 1 in 10.

  • If a student has selected the red bean, explain that it doesn’t mean the student will get flesh-eating disease but rather that the possibility still exists.
  • If no one selected a red bean, produce one yourself and explain that this represents the possibility that an individual will come down with flesh-eating disease.

6.

Instruct another student from each group to select a bean from the large container without looking.

  • Ask, “Did anyone get a red bean?”

Most likely, no one will have picked a red bean.

7.

Display this next to the “1/10”: “ 1/100.” Explain that the odds of picking a red bean from the large container were 1 in 100.

  • If a student has selected the red bean, explain that, as before, it doesn’t mean that the student will get flesh-eating disease but rather that the possibility still exists.
  • If no one selected a red bean, produce one yourself and explain that this represents the possibility that an individual will come down with flesh-eating disease.

8.

Instruct students to put the bean they selected back into the large container and remix the beans.

9.

One last time, instruct another student from each group to select a bean from the large container without looking.

  • Ask, “Did anyone get a red bean?”

As before, it is unlikely that a student will have picked a red bean.

10.

Display this next to the “1/100”: “ 1/100.” Explain that, just as last time, the odds of picking a red bean from the large container were 1 in 100.

11.

Explain that this activity modeled the 1 in 100,000 probability of coming down with flesh-eating disease. Display the answer to the probability calculation:

1/10 1/100 1/100 = 1/100,000

12.

Summarize by explaining that to reach the 1/100,000 odds of coming down with flesh-eating disease, a group would have had to pick the red bean from the small container and pick it again both times from the large container.

Note: Some students may wonder what it would look like to pick one red baby lima bean out of a pile of 100,000 beans. You may explain that 100,000 baby lima beans would weigh about 83 pounds and fill a large wheelbarrow.

13.

Conclude the lesson by asking,

  • “What are two reasons why flesh-eating disease is so rare?”
  • “Which two general causes of disease interacted to allow flesh-eating disease to develop?”

Students should comment that the bacteria responsible for flesh-eating disease are normally found in the throat and airways, but in the case of flesh-eating disease, the bacteria enter another part of the body through an open wound.

If not brought up by a student, mention that the vast majority of people don’t develop flesh-eating disease even when infected through an open wound. Most people’s immune systems stop the infection; but in rare cases, a person has an immune system that (because of genetics) allows the infection to become established. Also, people with weakened immune systems are at higher risk for infection.

Lesson 2 Organizer: Web Version

WWW Logo
Activity 1: Causes of Disease
Estimated time: 30 minutes
Page and Step
Explain that students will explore what causes rare diseases and assume the roles of medical officers in charge of the health of soldiers at an army post. Page 56
Steps 1 and 2
Arrange the class into pairs. Explain that they will look at a list of infirmary visits for the previous week and look for patterns that suggest a health concern. Page 56
Step 3
Give each pair a copy of Master 2.1, and instruct pairs to go to the Web site for the curriculum. Page 57
Step 4-w
Master
Instruct students to click on “Activity 1: Infirmary Visits, Week 1” and to think about the reasons why soldiers went to the infirmary. Page 57
Step 5a-w
WWW Logo
Ask, “What are two general reasons why soldiers reported to the infirmary?” Page 57
Step 5b-w
Remind students about the three general causes of disease:
  • infectious agents,
  • heredity (genetics), and
  • environmental toxins.
Ask, “Which of these three causes is most likely to be responsible for a health problem that can spread throughout the post?”
Page 58
Step 6
Display Master 2.1.
  • Ask for a volunteer to summarize the reasons that soldiers came to the infirmary.
  • Record and display these reasons.
  • Ask, “Do any patterns or cases worry you?”
Page 58
Steps 7 and 8
Transparency
Mention that one or more types of infectious disease may be present on the post. Ask, “How can we tell whether or not a soldier has a bacterial infection?” Page 58
Step 9
Explain that they can order tests for bacterial infections.
  • Test 1 looks for infections by bacterial species associated with pinkeye, sore throats, and infected cuts and abrasions.
  • Test 2 looks for infections associated with skin rashes caused by Rocky Mountain spotted fever or Lyme disease bacteria and for exposure to poison ivy.
Page 59
Step 10
Instruct pairs to return to the Web site, order the needed tests, and record on Master 2.1 which tests they ordered and why. Page 59
Step 11-w
WWW Logo
Ask students to click on “Activity 1: Lab Test Results.” Tell students to summarize in their notebooks those cases that could spread throughout the post and to describe how they were treated. Page 60
Steps 12-w and 13-w
Check mark


Activity 2: Is a Rare Disease Present?
Estimated time: 40 minutes
Page and Step
Explain that one week has gone by, and you are ready to discuss patient outcomes from Week 1.
  • Instruct pairs to go the Web site and click on “Activity 2: Follow-up on Week 1 Visits.”
  • Ask volunteers to summarize the outcomes described there.
Page 61
Steps 1-w and 2-w
WWW Logo
Ask, “Did you learn anything that causes you to be concerned?” Page 62
Step 3-w
Instruct pairs to click on “Activity 2: Infirmary Visits, Week 2” and then to summarize in their notebooks the reasons soldiers came to the infirmary. Page 62
Step 4-w
WWW Logo
Ask volunteers to report what they wrote in their notebooks, display their responses, and discuss. Page 63
Step 5
Ask, “Is there any evidence of a bacterial infection spreading throughout the post?” Page 63
Step 6
Explain that you are concerned about the serious foot infection.
  • Observe that bacterial species A seems to cause both sore throats and the foot infection.
  • Ask, “Can the same bacterial species be responsible for causing two different diseases?”
Page 64
Step 7
Explain that the foot infection could be caused by flesh-eating disease. Instruct students to look up the disease in the Medical Reference Manual. Page 64
Step 8
Give each pair a copy of Master 2.7. Instruct students to go to the Web site, click on “Activity 2: Medical Reference Manual,” and use the information there to answer the questions on Master 2.7. Page 64
Step 9-w
WWW Logo

Master
Ask volunteers to report their answers to the questions on Master 2.7. Page 65
Step 10


Activity 3: How Rare Is Rare?
Estimated time: 30 minutes
Page and Step
Observe that bacterial species A is common and causes strep throat. It can also cause the rare flesh-eating disease. Explain that the odds of getting flesh-eating disease are 1 in 100,000. Page 66
Step 1
Arrange the class in groups of four. Give each group
  • 1 small container with 9 baby lima beans and 1 baby lima bean colored red and
  • 1 large container with 99 baby lima beans and 1 baby lima bean colored red.
Page 66
Step 2
Display this statement: “The odds of coming down with flesh-eating disease this year are 1 in 100,000.” Page 66
Step 3
Explain that the red bean represents a person who may come down with flesh-eating disease.
  • Have one student from each group pick a bean from the small container without looking.
  • Ask, “Did anyone get a red bean?”
Page 66
Step 4
Display this: “1/10.” Explain that the odds of picking a red bean were 1 in 10. Page 66
Step 5
Have another student from each group pick a bean from the large container. Ask, “Did anyone get a red bean?” Page 66
Step 6
Display this next to 1/10: “ 1 /100.” Explain that the odds of picking a red bean were 1 in 100. Page 66
Step 7
Tell students to place the selected beans back into the large container and mix. Have another student once again pick a bean from the large container. Ask, “Did anyone get a red bean?” Page 67
Steps 8 and 9
Display next to 1 /100, “ 1 /100.” Explain that, as before, the odds of picking a red bean were 1 in 100. Page 67
Step 10
Explain that this activity modeled the 1 in 100,000 probability of coming down with flesh-eating disease.
  • Display the answer to the probability calculation:
    “1/10 1/100 1/100 = 1/100,000.”
  • Explain that to get flesh-eating disease, a group would have had to pick the red bean from the small container and pick it again both times from the large container.
Page 67
Steps 11 and 12
Conclude the lesson by asking,
  • “What are two reasons why flesh-eating disease is so rare?”
  • “Which two general causes of disease interacted to allow flesh-eating disease to develop?”
Page 67
Step 13

 

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Transparency = Involves making a transparency.

Lesson 2 Organizer: Print Version

Open book
Activity 1: Causes of Disease
Estimated time: 30 minutes
Page and Step
Explain that students will
  • explore what causes rare diseases and
  • assume the roles of medical officers in charge of the health of soldiers at an army post.
Page 56
Steps 1 and 2
Arrange the class into pairs. Explain that they will look at a list of infirmary visits for the previous week and look for patterns that suggest a health concern. Page 56
Step 3
Give each pair a copy of Masters 2.1 and 2.2, and ask students to read over the reasons for the visits. Page 57
Step 4-p
Master
Ask, “What are two general reasons why soldiers reported to the infirmary?” Page 57
Step 5-p
Remind students about the three general causes of disease:
  • infectious agents,
  • heredity (genetics), and
  • environmental toxins.
Ask, “Which of these three causes is most likely to be responsible for a health problem that can spread throughout the post?”
Page 58
Step 6
Display Master 2.1.
  • Ask a volunteer to summarize the reasons that soldiers came to the infirmary.
  • Record and display these reasons.
  • Ask, “Do any patterns or cases worry you?”
Page 58
Steps 7 and 8
Transparency
Mention that one or more types of infectious disease may be present on the post. Ask, “How can we tell whether or not a soldier has a bacterial infection?” Page 58
Step 9
Explain that people can order tests for bacterial infections.
  • Test 1 looks for infections by bacterial species associated with pinkeye, sore throats, and infected cuts and abrasions.
  • Test 2 looks for infections associated with skin rashes caused by Rocky Mountain spotted fever or Lyme disease bacteria and for exposure to poison ivy.
Page 59
Step 10
Instruct pairs to decide and then record on Master 2.1 which lab tests (if any) to order for which soldiers and why. Page 60
Step 11-p
Give each pair a copy of Master 2.3. Ask students to summarize in their notebooks the cases that could spread throughout the post and to describe how they were treated. Page 61
Steps 12-p and 13-p
Master


Activity 2: Is a Rare Disease Present?
Estimated time: 40 minutes
Page and Step
Explain that one week has gone by, and you are ready to discuss patient outcomes from Week 1 and to present a list of new infirmary visits. Give each student pair a copy of Master 2.4, and ask students to look it over. Page 62
Steps 1-p and 2-p
Master
Ask, “Did you learn anything that causes you to be concerned?” Page 63
Step 3-p
Give each pair a copy of Master 2.5, and ask students to look it over. Instruct pairs to summarize in their notebooks the reasons soldiers came to the infirmary. Page 63
Step 4-p
Master
Ask volunteers to report what they wrote in their notebooks, display their responses, and discuss. Page 63
Step 5
Ask, “Is there any evidence of a bacterial infection spreading throughout the post?” Page 63
Step 6
Explain that you are concerned about the serious foot infection.
  • Observe that bacterial species A seems to cause both sore throats and the foot infection.
  • Ask, “Can the same bacterial species be responsible for causing two different diseases?”
Page 64
Step 7
Explain that the foot infection could be caused by flesh-eating disease. Instruct students to look up the disease in the Medical Reference Manual. Page 64
Step 8
Give each pairs a copy of Masters 2.6 and 2.7. Instruct students to use Master 2.6 to answer the questions on Master 2.7. Page 64
Step 9-p
Master
Ask volunteers to report their answers to the questions on Master 2.7. Page 65
Step 10


Activity 3: How Rare Is Rare?
Estimated time: 30 minutes
Page and Step
Observe that bacterial species A is common and causes strep throat. It can also cause the rare flesh-eating disease. Explain that the odds of getting flesh-eating disease are 1 in 100,000. Page 66
Step 1
Arrange the class in groups of four. Give each group
  • 1 small container with 9 baby lima beans and 1 baby lima bean colored red and
  • 1 large container with 99 baby lima beans and 1 baby lima bean colored red.
Page 66
Step 2
Display this statement: “The odds of coming down with flesh-eating disease this year are 1 in 100,000.” Page 66
Step 3
Explain that the red bean represents a person who may come down with flesh-eating disease.
  • Have one student from each group pick a bean from the small container without looking.
  • Ask, “Did anyone get a red bean?”
Page 66
Step 4
Display this: “1/10.” Explain that the odds of picking a red bean were 1 in 10. Page 66
Step 5
Have another student from each group pick a bean from the large container. Ask, “Did anyone get a red bean?” Page 66
Step 6
Display this next to 1/10: “ 1 /100.” Explain that the odds of picking a red bean were 1 in 100. Page 66
Step 7
Tell students to place the selected beans back into the large container and mix. Have another student once again pick a bean from the large container. Ask, “Did anyone get a red bean?” Page 67
Steps 8 and 9
Display next to 1 /100, “ 1 /100.” Explain that, as before, the odds of picking a red bean were 1 in 100. Page 67
Step 10
Explain that this activity modeled the 1 in 100,000 probability of coming down with flesh-eating disease.
  • Display the answer to the probability calculation:
    “1/10 1/100 1/100 = 1/100,000.”
  • Explain that to get flesh-eating disease, a group would have had to pick the red bean from the small container and pick it again both times from the large container.
Page 67
Steps 11 and 12
Conclude the lesson by asking,
  • “What are two reasons why flesh-eating disease is so rare?”
  • “Which two general causes of disease interacted to allow flesh-eating disease to develop?”
Page 67
Step 13

 

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