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Infectious Disease Case Study

Infectious Disease Case Study
  • Grades:
  • Length: 60 Minutes


Students use evidence to determine whether a patient has a cold, flu or strep infection, and they also learn the differences between bacterial and viral infections.

This activity is from The Science of Microbes Teacher's Guide, and is most appropriate for use with students in grades 6-8. Lessons from the guide may be used with other grade levels as deemed appropriate.

The guide is available in print format.

This work was developed in partnership with the Baylor-UT Houston Center for AIDS Research, an NIH-funded program.

Teacher Background

Many different microorganisms can infect the human respiratory system, causing symptoms such as fever, runny nose or sore throat. Even the common cold, which may range from mild to serious, can be caused by any of more than 200 viruses! Colds are among the leading causes of visits to physicians in the United States, and the Centers for Disease Control and Prevention (CDC) report that 22 million school days are lost in the U.S. each year due to the common cold. Usually, cold symptoms appear within two to three days of infection and include: mucus buildup in the nose, swelling of sinuses, cough, headache, sore throat, sneezing and mild fever (particularly in infants and young children). The body’s immune system, which protects against disease-causing microbes, almost always is able to eliminate the viruses responsible for a cold.

Flu (or influenza) often is more serious than the common cold. Caused by one of three types of closely related viruses, flu can come on quickly, with chills, fatigue, headache and body aches. A high fever and severe cough may develop. Flu may be prevented in some cases through a vaccine. However, since the viruses that cause flu change slightly from year to year, a new vaccine is required each flu season. Influenza was responsible for three pandemics (worldwide spread of disease) in the 20th Century alone.

Antibiotics do not kill viruses, and therefore, are not helpful in fighting the common cold or flu. But these diseases can make a person more susceptible to bacterial infections, such as strep throat, a common infection by a Streptococcus bacterium. Symptoms of “strep” infections include sore throat, high fever, coughing, and swollen lymph nodes and tonsils. Diagnosis should be based on the results of a throat swab, which is cultured, and/or a rapid antigen test, which detects foreign substances, known as antigens, in the throat. Strep infections usually can be treated effectively with antibiotics. Without treatment, strep throat can lead to other serious illnesses, such as scarlet fever and rheumatic fever.

Symptoms similar to those of a cold can be caused by allergens in the air. Health experts estimate that 35 million Americans suffer from respiratory allergies, such as hay fever (pollen allergy). An allergy is a reaction of an individual’s disease defense system (immune system) to a substance that does not bother most people. Allergies are not contagious.

Objectives and Standards


  • Develop descriptions, explanations, predictions and models using evidence.

  • Think critically and logically to make the relationships between evidence and explanations.

  • Recognize and analyze alternative explanations and predictions.

Life Science

  • Disease is a breakdown in structures or functions of an organism. Some diseases are the result of infection by other organisms.

Materials and Setup

Teacher Materials (see Setup)

  • 90 letter-size plain envelopes

  • 6 sheets of white, self-stick folder labels, 3-7/16 in. x 2/3 in., 30 labels per sheet (Avery™ #5366, 5378 or 8366)

  • Overhead projector

  • Overhead transparency of the "Disorders and Symptoms" student sheet

Materials per Group of Students

  • Set of prepared envelopes (15 envelopes per set)

  • Copy of "What is Wrong with Allison?" and "Disorders and Symptoms" student sheets (see Lesson pdf)

  • Group concept map (ongoing)


  1. Photocopy the "What is Wrong with Allison?" and "Disorders and Symptoms" student sheets (one copy of each per student), to be distributed in order (see Procedure).

  2. Photocopy the label template sheet onto six sheets of white, self-stick labels, such as Avery™ #5366, 5378 or 8366, which contain 30 labels per sheet.

  3. Use one page of photocopied labels to create each set of envelopes. Place a "Question" label on the outside of one envelope and stick the corresponding "Clue" label on the inside flap of the same envelope. Close the flap, but do not seal the envelope. Make six sets of 15 envelopes (one set per group).

  4. Make an overhead transparency of the "Disorders and Symptoms" sheet. Have students work in groups of four.

  5. Optional: Instead of using self-stick labels, copy the label template page onto plain paper and cut out each question and clue. Tape one question to the outside of an envelope and the corresponding clue to the inside flap of the envelope.

Procedure and Extensions

  1. Begin a class discussion of disease by asking questions such as, How do you know when you are sick? What are some common diseases? Are all diseases alike? Are all diseases caused by a kind of microbe? Do some diseases have similar symptoms?

  2. Tell your students that in this class session, they will be acting as medical personnel trying to diagnose a patient. Give each group a copy of the "What is Wrong with Allison?" sheet. Have one student read the case to the group, and then have groups discuss it. The reporter should record each group’s ideas about what might be wrong with Allison.

  3. Have each student group list four possible questions that a doctor might ask a patient like Allison. Write these questions on the board and discuss with the class.

  4. Have groups identify three possible diseases that Allison may have, based on the story, class discussion and their own experiences.

  5. Give each student a copy of the "Disorders and Symptoms" sheet and briefly introduce the four illnesses to the entire class. Compare these illnesses to the ones that students suggested. Ask, Are there any similarities? Have students follow the instructions on the sheet to complete the exercise.

  6. Give each group of students a set of envelopes. Warn students not to open the envelopes until they are instructed to do so. Tell students that each envelope contains information that a medical doctor might need about a patient. All information is important to the diagnosis, but only certain information will help to distinguish among the four possible respiratory disorders. Instruct students that their task is to decide which envelopes contain information that will help them determine Allison’s illness. Once a group has agreed on question choices, it may open as many envelopes—one at a time—as needed. The challenge is to use as few envelopes as possible to diagnose Allison’s illness. Each group should keep a tally of the number of envelopes opened. Remind students that in real life, a physician would conduct a complete examination and gather all possible information before making a diagnosis.

  7. Allow time for groups to work. Provide assistance to students who may not understand the information contained in the envelopes. If the medicine and body temperature envelopes have been opened, make sure students understand that some medications, like Tylenol™, will mask the presence of mild fevers.

  8. Have each group present its diagnosis and the reasoning used to arrive at its decision. (Allison’s disease is a common cold. If students have arrived at other conclusions, discuss the evidence they used. Mention the challenges of diagnosing respiratory diseases.)

  9. Expand the discussion to address the importance of not taking antibiotics for viral diseases. Ask, Since Allison has a cold, should her doctor prescribe antibiotics? Would it be okay to take leftover antibiotics? Help students understand that antibiotics are effective for bacterial infections, but do not help against viral infections like colds.

    Also, mention that if antibiotics are prescribed for a bacterial infection, it is important to follow the doctor’s instructions and to take all the medication, even if symptoms start to improve before the medicine is gone. Otherwise, the disease may reoccur. Taking antibiotics incorrectly, or using them inappropriately (such as taking leftover medicine without a doctor’s guidance) can contribute to the development of antibiotic resistant forms of bacteria, which cannot be killed by existing antibiotics.

  10. Have student groups add information to their concept maps.

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Science Education Partnership Award, NIH

Science Education Partnership Award, NIH

Grant Number: 5R25RR018605