Sign up for updates

Skip Navigation

What Are Infectious Diseases?

A Look at Illnesses Around the World

What are Infectious Diseases?
  • Grades:
  • Length: 90 Minutes

Rate this Page

Average Rating (2 votes)

View Comments


Students will conduct research using online text resources and media related to infectious and non-infectious diseases and compare the prevalence of different diseases across countries with different income levels. Students will apply coronavirus disease information from the World Health Organization to learn how disease spread is monitored and compare the status of different countries.


Teacher Background

Students will apply COVID-19 information from the World Health Organization to learn how disease spread is monitored and compare the status of different countries.

Objectives and Standards

After completing the unit, students will be able to:

  1. Explain what an infectious disease is

  2. Describe the types of diseases that cause the most deaths worldwide

  3. Explain how a country’s income level relates to the types of diseases most common in that country


Science/Health/Math Skills


Interpreting information




NGSS Science & Engineering Practices

Analyzing and interpreting data

Obtaining, evaluating and communicating information


Common Core Standards for English Language Arts
ELA-LITERACY.RST.9-10.1. Cite specific textual evidence to support analysis of science and technical texts, attending to the precise details of explanations or descriptions.

ELA-LITERACY.RST.9-10.2. Determine the central ideas or conclusions of a text; trace the text's explanation or depiction of a complex process, phenomenon, or concept; provide an accurate summary of the text.


Materials and Setup

Each student will need:

Copy of the Student Research Guide (digital or paper) on which to record answers.

Device with Internet access

Teacher will need the accompany slides to guide student discussion


Set Up and Teaching Tips

This activity can be introduced during one classroom period and completed during the next time you meet with students. Use the accompanying slides to guide a discussion of students’ independent research using informational texts and media.


Procedure and Extensions

Engage & Explore

  1. Tell students that they are going to learn what an infectious disease is and how infectious diseases impact mortality (human deaths) around the world.

  2. Ask students to complete the “What are Infectious Diseases” Student Activity Sheet before the next class.


  1. Use the accompanying slides to review what students learned from their activity sheet explorations. If students raise a question for which you do not have an answer, have them add it to a “what I want to know” list. You can suggest a possible online source, such as the Centers for Disease Control and Prevention (CDC) or World Health Organization (WHO), which might provide the information.

Note: Slide 4 is optional. If you want to include a formal evaluation with this activity, you may choose to hide the slide and use it afterward with students as an assessment.

Slide 2: What is an infectious disease? 

  • Merriam-Webster dictionary defines “disease” as “a condition of the living animal or plant body or of one of its parts that impairs normal functioning and is typically manifested by distinguishing signs and symptoms.”[1]
  • Diseases can be “communicable” or “non-communicable.”
  • Communicable diseases result from the passing of a pathogen (an infectious agent, such as a bacterium, virus, fungi, or parasite) from an infected individual to another individual or group.[2]
  • Well-known communicable diseases include tuberculosis, influenza (flu), and strep throat.
  • Some communicable diseases, called “zoonotic” diseases, can pass from animals to humans.
  • Non-communicable diseases do not pass directly from one person to another. Examples include diabetes, Alzheimer’s disease, Parkinson’s disease, osteoarthritis, and most cancers. Non-communicable diseases often are “chronic,” lasting a year or more and requiring ongoing medical attention.[3]

Slide 3: World’s top killers

  • What are the top killers, the deadliest diseases, in the world?
  • The World Health Organization (WHO) collects global data each year to learn how many people in different countries have certain diseases, and how many deaths each disease causes.
  • The WHO have a numbering system to categorize every type of disease and health condition, and they receive reports from nearly every country to track global health problems.
  • You viewed WHO graphs of the top 10 causes of death in 2010 and 2016 to learn if there were any changes over this 16-year period.
  • The main categories of diseases were:
    • communicable, maternal, neonatal, and nutritional conditions
    • non-communicable diseases
    • injuries
  • Hypothesis #1 stated that the top 10 causes of death worldwide remained the same between 2000 and 2016. What did you learn?
    • Non-communicable diseases: ischemic heart disease, stroke, COPD, and respiratory system cancers were on both lists, but by 2016, Alzheimer’s and other dementias, along with diabetes, became top causes of death.
    • Communicable diseases: lower respiratory infections, diarrheal infections and tuberculosis were on both lists, but by 2016, HIV/AIDS and preterm birth complications were no longer among the top 10 causes of death.
    • Injuries: road injuries remained on both lists.
  • Hypothesis #2: Communicable diseases (along with diseases related to birth and nutrition) were the primary cause of death worldwide in both 2000 and 2016.
    • Far more deaths are attributed to non-communicable diseases (e.g., heart disease, stroke, and COPD) than to respiratory diseases.
    • However, there were fewer deaths from communicable diseases in 2016 than in 2000[PSM1] .

Slide 4: Does money make a difference?

  • Hypothesis #3: The primary causes of death in 2016 were not related to the income level of the country.
  • What were your conclusions?
    • In general, as the overall income of a country increases, noncommunicable diseases are more likely to be the cause of death. In poorer countries, communicable diseases contribute more to mortality.
    • Three causes of death were in the top 10 in all country income groups: heart disease, stroke, and lower respiratory infections.
  • If you were in charge of national medical resources and public health, what would be your top priorities to reduce the death rate in countries of each income type, based on what you learned?
  • COVID-19 is a lower respiratory infection. Which group(s) of countries might you expect to see especially hard hit by the COVID-19 pandemic, and why?
    • Poorer countries might be hit hard because they don’t have as many resources to deal with a pandemic. However, they deal with a lot of infectious diseases cases and may have proportionally more medical personnel trained for infectious diseases treatment.
    • Wealthier countries have more resources, but since most deaths in those countries are due to non-communicable diseases, their medical facilities, supplies, and staff may be more focused on those diseases.

Slide 6: Why are the causes of death changing?

  • In 1900, US citizens lived to an average age of 47.3 years.
  • Primary causes of death were communicable disease: pneumonia, influenza, tuberculosis, diphtheria, smallpox, pertussis (whooping cough), and typhoid fever.
  • Vaccinations, improved hygiene, and antibiotics all played a role in changing this.
  • Since 1924, vaccines have prevented 40 million cases of diphtheria, 35 million cases of measles, and 103 million cases of childhood diseases.
  • As of 2014, life expectancy in the US is 78.7 years.
  • In the US, primary causes of death are heart disease, stroke, and cancer.[4]

Slide 7: Why do we get new infectious diseases?

  • Pandemics of infectious diseases have been recorded in history as far back as 450 BC, when the “Plague of Athens” killed 100,000 people.
  • The Black Death (Yersinia pestis) killed half of the world’s population in 541 AD, and a quarter of world’s population in the 1340s.
  • Tuberculosis became a pandemic in the Middle Ages (1500 AD) and killed millions.
  • Smallpox killed millions after it was brought to the New World by European explorers.
  • The 1918 Spanish influenza killed approximately 50 million worldwide, including 675,000 in the US.
  • In the last 50 years, the world has experienced pandemics and near-pandemics of Ebola, HIV-AIDS, SARS, H1N1 “swine flu”, and mosquito-borne viruses (Zika virus and Chikungunya).
  • Some infectious diseases move from animal populations (where they may not be as deadly) to humans through animal-human contact. Ebola and coronaviruses are examples.
  • Some infectious disease viruses mutate frequently, preventing the human immune system developing lasting protection (“immunity”). Influenza is an example.
  • Finally, changing human behaviors have had a major impact on disease spread. Exploration and work in areas that were previously inaccessible brings humans into first or regular contact with novel creatures, microbes, and viruses. Second, easy access to worldwide travel often enables contagious diseases to spread quickly and before the public health community recognizes the disease and its spread.

Slide 8: The COVID-19 Pandemic

  • An “epidemic” is the sudden increase in cases of an infectious disease in an area or country. When a disease spreads to several countries and affects large number of people, it is called “pandemic”[5]
  • The World Health Organization (WHO) tracks epidemic and pandemic cases by country, as you learned from your Activity Sheet exercise.
  • What could you learn from looking at “total cases” in different countries?
  • What could you learn from looking at “total cases per million persons” in different countries?
  • Which metric (total cases, or total cases per 1 million people) do you think is a better measure, and why?
  • It depends on what other questions you want to answer. If you want to know which countries will need a vaccine and how many doses they will need, you need to know the total population, the number of cases, and where those cases are concentrated. If you want to know whether the strategies used by different countries are working, you may want to look at the total cases per million people.
  • For example, China was able to keep the number of COVID-19 cases relatively low. But most countries would not use the same methods as China did, such as putting extreme limits on travel and prohibiting people from leaving their homes for periods of time, even to walk their dogs.


Have students use three additional graphs on the WHO website ( to determine whether the most common causes of death around the world are influenced by a country’s affluence (overall income levels). Results are provided below and on Slide 4 (described above).

  1. Hypothesis #3: The primary causes of death in 2016 were not related to the income level of the country.

    1. Using the table that you created, what evidence do you see to support or disprove Hypothesis #3?

    2. What is/are your conclusion(s)?

    3. What three causes of death were in the top-10 in all country income groups?

    4. If you were in charge of national medical resources and public health, what would be your top priorities to reduce the death rate in countries of each income group, based on what you learned?

      1. Low- income countries

      2. Lower-middle income countries

      3. Upper-middle income countries

      4. High income countries:

    5. COVID-19 is a lower respiratory infection. Which group(s) of countries might you expect to see especially hard hit by the COVID-19 pandemic and why?

top-10 cause of death in countries table

[4] Rappuoli, R., Pizza, M., Del Giudice, G., & De Gregorio, E. (2014). Vaccines, new opportunities for a new society. Proceedings of the National Academy of Sciences of the United States of America111(34), 12288–12293.

 [PSM1]There is no section that correlates to the student document on Explore and the website: WHO site on COVID dashboard

There is also not a slide that corresponds to the dashboard

Related Content

  • Infectious Disease Case Study

    Infectious Disease Case Study Lesson

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


The COVID HACKS curriculum project is made possible thanks to the support from Laura & John Arnold and Baylor College of Medicine. Scientists, educators and physicians from Baylor College of Medicine provided content, feedback and technical reviews.