Lesson
In 2022, the Australian Institute of Health and Welfare reported that 4.2 million Australians visited a GP for an infectious illness, yet the country's leading killers, heart disease and cancer, cannot be caught from anyone.
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Q1 · What is the difference between an infectious disease and a non-infectious disease? Give one example of each.
Q2 · If you feel sick after skipping breakfast and staying up late, does that mean you have a disease? Explain your thinking.
â—Ź Know
- The definition of disease and disorder
- The difference between infectious and non-infectious disease
- Examples of each type of disease
â—Ź Understand
- Why distinguishing disease type matters for treatment
- How diseases affect the body at different levels
- The relationship between symptoms and disease
â—Ź Can do
- Classify diseases as infectious or non-infectious
- Explain what disease means in scientific terms
- Give examples of diseases from each category
Wrong: "All diseases are caused by germs." No, many diseases are non-infectious. Cancer, diabetes, asthma, and genetic disorders are not caused by germs and cannot be caught from someone else.
Right: Many diseases are non-infectious and arise from genetics, lifestyle, or environmental factors rather than germs. These conditions cannot spread between people.
Wrong: "If you feel sick, you must have a disease." Not always. Feeling sick can be caused by temporary conditions like hunger, tiredness, or anxiety. Disease involves a specific disruption of normal body function.
Right: Feeling unwell can be temporary and caused by factors like hunger, tiredness, or stress. A true disease involves an ongoing disruption of normal body function rather than a fleeting discomfort.
Wrong: "Non-infectious diseases are less serious than infectious diseases." No, non-infectious diseases like heart disease and cancer cause far more deaths worldwide than infectious diseases.
Right: Non-infectious diseases such as heart disease, stroke, cancer, and diabetes cause roughly 74 percent of all deaths worldwide, making them the leading global health burden.
Disease Types
In science, disease is not just "feeling unwell." It is a condition that impairs the normal functioning of the body or mind.
Diseases can be caused by many things:
- Pathogens (bacteria, viruses, fungi, protists)
- Genetic factors (inherited conditions)
- Lifestyle choices (diet, exercise, smoking)
- Environmental exposure (radiation, toxins, pollutants)
- Immune system malfunction (autoimmune diseases)
Importantly, disease is different from injury. A broken bone or a cut is damage, not disease. Disease involves some ongoing process that disrupts normal body function.
Disease is a that impairs the normal functioning of the body or mind. Unlike a broken bone, which is an , disease involves an ongoing that disrupts normal body function.
Picture a Year 9 student in Sydney sneezing in a packed bus on a Monday morning, by Friday, six of her classmates have runny noses and a temperature. That chain of transmission is the hallmark of infectious diseases: caused by pathogens, they can spread from one organism to another and are also called communicable diseases.
Examples include:
- Common coldcaused by viruses (rhinoviruses)
- Influenzacaused by influenza viruses
- COVID-19caused by SARS-CoV-2 virus
- Tuberculosiscaused by Mycobacterium tuberculosis bacteria
- Malariacaused by Plasmodium protists, spread by mosquitoes
Infectious diseases can spread through the air, water, direct contact, or via vectors (organisms that carry pathogens). This is why isolation, handwashing, and vaccination are so important.
Non-infectious diseases are not caused by pathogens and cannot spread from person to person. They are also called non-communicable diseases (NCDs).
Major categories include:
- Lifestyle diseases: Cardiovascular disease, type 2 diabetes, obesity (linked to diet, exercise, smoking)
- Genetic diseases: Cystic fibrosis, Huntington's disease, sickle cell anaemia (inherited from parents)
- Environmental diseases: Asthma, some cancers (linked to pollution, radiation, toxins)
- Degenerative diseases: Alzheimer's, osteoarthritis (body tissues break down over time)
Non-infectious diseases are the leading cause of death worldwide. According to the World Health Organization, NCDs cause about 74% of all deaths globally.
| Feature | Infectious Disease | Non-Infectious Disease |
|---|---|---|
| Cause | Pathogen (bacteria, virus, etc.) | Genetics, lifestyle, environment |
| Spread | Can spread between organisms | Cannot spread |
| Examples | Flu, COVID-19, malaria | Diabetes, asthma, cancer |
| Prevention | Vaccination, hygiene, isolation | Healthy lifestyle, screening |
| Treatment | Antibiotics, antivirals | Lifestyle changes, medication, surgery |
Understanding whether a disease is infectious or non-infectious is crucial because it determines how we prevent and treat it. You cannot catch diabetes from someone, but you can catch influenza.
- Caused by pathogens
- Cannot spread between people
- Prevented by vaccination
- Treated with lifestyle changes
- Examples include flu and malaria
- Non-infectious
- Infectious
- Infectious
- Infectious
- Non-infectious
Before checking the statistics, predict which type of disease causes more deaths worldwide: infectious diseases or non-infectious diseases. Then reveal the answer.
How close was your prediction?
Nice calibration, your intuition is good for this kind of problem.
Good, being surprised is the point. This answer is worth remembering.
At the start of this lesson, you were asked about why millions of Australians visit a GP each year for infectious illness, yet conditions like diabetes and asthma never spread from person to person.
Now that you've worked through the lesson, can you explain what actually makes a disease infectious or non-infectious? How has your understanding of that distinction changed or deepened?
Q1. 1. Define disease and explain the difference between infectious and non-infectious diseases. Give two examples of each. 4 MARKS
Q2. 2. Explain why cardiovascular disease and malaria require completely different public health responses. Use your knowledge of disease types. 4 MARKS
Q3. 3. A student claims that all serious diseases are infectious. Evaluate this statement using evidence. 4 MARKS
Answers
â–ľMCQ 1
CInfluenza is caused by a virus and can spread from person to person, making it an infectious disease.
MCQ 2
BInfectious diseases are caused by pathogens and can spread between organisms. Non-infectious diseases cannot spread.
MCQ 3
BAn infectious disease is caused by a pathogen and can spread between organisms.
MCQ 4
CType 2 diabetes is a non-infectious disease linked to lifestyle factors such as diet and exercise.
MCQ 5
BKnowing whether a disease is infectious determines prevention strategies (vaccination, hygiene) and treatment approaches.
Short Answer 1
Model answer: A disease is a condition that impairs the normal functioning of the body or mind. An infectious disease is caused by a pathogen (such as bacteria, viruses, fungi, or protists) and can spread from one organism to another. Examples include influenza (caused by a virus) and tuberculosis (caused by bacteria). A non-infectious disease is not caused by a pathogen and cannot spread between organisms. Examples include type 2 diabetes (linked to lifestyle factors) and asthma (linked to genetics and environment).
Short Answer 2
Model answer: Cardiovascular disease is a non-infectious disease, so public health responses focus on lifestyle interventions: promoting healthy diets, encouraging exercise, reducing smoking rates, and screening for risk factors like high blood pressure. Malaria is an infectious disease caused by a protist and spread by mosquitoes, so public health responses focus on controlling the vector (insecticide-treated bed nets, draining standing water), providing antimalarial medication, and rapid diagnosis. The fundamental difference is that malaria can spread through a population via mosquitoes, while cardiovascular disease spreads only through shared risk factors, not direct transmission.
Short Answer 3
Model answer: This statement is incorrect. Many of the most serious and deadly diseases worldwide are non-infectious. According to the World Health Organization, non-communicable diseases (cardiovascular disease, cancer, chronic respiratory diseases, and diabetes) cause approximately 74% of all deaths globally. In Australia, cardiovascular disease is the leading cause of death. While infectious diseases like COVID-19 and malaria can be devastating, non-infectious diseases are responsible for more deaths overall. Seriousness depends on the specific disease, its stage, and available treatments, not on whether it is infectious or non-infectious.