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Author(s): Nancy Moreno, PhD, Barbara Tharp, MS, Deanne Erdmann, MS, Sonia Rahmati Clayton, PhD, and James Denk, MA.

Infectious Disease Case Study

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.


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 (see PDF). 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 & Symptoms” sheet (see next slide) 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. 

Funded by the following grant(s)

Science Education Partnership Award, NIH

Grant Number: 5R25RR018605