Year 9 Science Unit 1 · Disease Lesson 4 of 20 45 min SC5-DIS-04

Disease in Australia

Australia is one of the healthiest nations on Earth, but disease still shapes our lives. From mosquito-borne viruses in the tropics to food poisoning outbreaks in cities, understanding disease patterns in Australia helps us stay safe and healthy.

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Think First

Before You Begin

A cluster of people in a small town all develop the same stomach illness within two days of eating at the same cafe.

Write down your answers before reading on:

  • What do you think caused the outbreak?
  • How would you find out for sure?
  • Who would be responsible for investigating this?
Write your thinking in your book before reading on.

Work mode: Digital — answers typed below

Learning Intentions

Know

  • Common infectious diseases in Australia
  • The basics of epidemiology and disease surveillance
  • How outbreak investigations work

Understand

  • Why disease patterns differ across regions of Australia
  • How data is used to track and control disease
  • The role of public health organisations in disease control

Can Do

  • Interpret basic epidemiological data
  • Describe how an outbreak is investigated
  • Identify Australian organisations responsible for disease tracking
Key Terms
Epidemiology The study of patterns, causes, and effects of disease in populations.
Outbreak The sudden occurrence of a disease in a community or region at a rate above what is normally expected.
Endemic A disease that is consistently present in a particular population or region at a baseline level.
Surveillance The ongoing systematic collection, analysis, and interpretation of health data.
Contact tracing Identifying and monitoring people who may have been exposed to an infected person.
Incidence The number of new cases of a disease in a population over a specific time period.
Core Content
1

Infectious Diseases in Australia

What affects Australians today

Fungi Protozoa

Fungi Protozoa

Australia has low rates of many infectious diseases compared to developing nations, thanks to good sanitation, vaccination, and healthcare. However, infectious diseases remain a significant health concern.

Common infectious diseases in Australia include:

  • Influenza: 200,000+ cases and hundreds of deaths annually
  • COVID-19: Caused significant illness and death since 2020
  • Ross River virus: Most common mosquito-borne disease, mainly in rural areas
  • Foodborne illness: An estimated 4.1 million cases of food poisoning each year
  • Sexually transmitted infections: Chlamydia is the most commonly reported STI
  • Whooping cough (pertussis): Cyclic outbreaks despite vaccination

Many of these diseases are preventable through vaccination, hygiene, and safe food handling.

2

Epidemiology 101

The science of disease detectives

Epidemiology is the study of how diseases spread and affect populations. Epidemiologists are like disease detectives — they investigate outbreaks, track disease trends, and design strategies to control disease.

Key concepts in epidemiology:

  • Incidence: The number of new cases in a population over time
  • Prevalence: The total number of cases (new and existing) at a given time
  • Mortality rate: The number of deaths from a disease per population
  • Morbidity: The state of being diseased or unwell

Epidemiologists use data from hospitals, laboratories, and disease notifications to build a picture of disease in the community. This data guides public health decisions, such as whether to recommend vaccination campaigns or issue health warnings.

3

Outbreak Investigation

How disease detectives solve the case

When an outbreak occurs, epidemiologists follow a systematic process to find the cause and stop the spread:

  1. Verify the diagnosis: Confirm that the cases really have the same disease
  2. Confirm the outbreak: Determine if the number of cases exceeds normal levels
  3. Define a case: Create clear criteria for who counts as a case
  4. Find cases: Identify all people who meet the case definition
  5. Generate hypotheses: Develop possible explanations for the outbreak
  6. Test hypotheses: Collect and analyse data to test each explanation
  7. Implement control measures: Take action to stop further spread
  8. Communicate findings: Report results to the public and health authorities

Contact tracing is a key tool — identifying everyone who may have been exposed to an infected person so they can be tested, treated, or isolated.

4

Australian Disease Surveillance

Who watches over our health

Australia has a comprehensive disease surveillance system:

National Notifiable Diseases Surveillance System (NNDSS): All states and territories report cases of about 70 notifiable diseases to this national database. This allows rapid detection of outbreaks and trends.

Australian Institute of Health and Welfare (AIHW): Collects and reports data on health and wellbeing, including disease statistics, risk factors, and health service use.

Communicable Diseases Network Australia (CDNA): Coordinates national responses to communicable disease threats. During the COVID-19 pandemic, CDNA provided daily updates and guidance.

State and territory health departments: Each state runs its own surveillance, outbreak investigation, and public health response. For example, NSW Health and Queensland Health manage local disease control.

Common Misconceptions

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"Australia does not have any serious infectious diseases." No — while Australia has lower rates than many countries, infectious diseases still cause significant illness. Influenza kills hundreds of Australians annually, and foodborne illness affects millions.

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"Epidemiologists only work during pandemics." No — epidemiologists work year-round tracking diseases, investigating outbreaks, and designing prevention programs. Their work is essential even when there is no pandemic.

✗trong>"Contact tracing is only for COVID-19." No — contact tracing is used for many diseases, including tuberculosis, measles, meningococcal disease, and sexually transmitted infections.

Australian Context

Fighting Disease Across Australia

The 2022 Japanese encephalitis outbreak: In early 2022, Japanese encephalitis virus — never before seen in southern Australia — was detected in piggeries across Victoria, New South Wales, South Australia, and Queensland. The outbreak, linked to flooding and increased mosquito populations, prompted emergency vaccination programs for at-risk workers and demonstrated how climate change is expanding the range of vector-borne diseases.

Foodborne illness surveillance: OzFoodNet, Australia's foodborne disease surveillance network, tracks outbreaks of food poisoning across the country. In 2019, a nationwide outbreak of Salmonella was traced to contaminated eggs, leading to recalls and improved food safety standards. This shows how surveillance protects the entire population.

Remote and Indigenous health: Disease patterns in remote Aboriginal and Torres Strait Islander communities differ significantly from urban Australia. Higher rates of rheumatic heart disease, trachoma, and skin infections reflect social determinants of health including overcrowded housing and limited access to healthcare. The Rheumatic Heart Disease Australia registry tracks cases to guide prevention programs.

✍ Copy Into Your Books

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Key Terms

  • Epidemiology = study of disease in populations
  • Incidence = new cases over time
  • Outbreak = more cases than expected

Australian Diseases

  • Influenza: 200,000+ cases/year
  • Ross River virus: most common mosquito-borne
  • Foodborne illness: ~4.1 million cases/year

Outbreak Steps

  • Verify diagnosis -> Confirm outbreak -> Define cases -> Find cases -> Hypothesise -> Test -> Control -> Communicate
Activities
Activity 1

Data Detective

Practise interpreting disease data.

1 The NNDSS reports 50 cases of measles in a state over one month when the usual average is 2 cases per month. Is this an outbreak? Justify your answer.
Answer in your book.
2 A town of 10,000 people has 200 new cases of influenza in one month. Calculate the incidence rate per 1,000 people. Show your working.
Answer in your book.
3 Explain why contact tracing was essential during the COVID-19 pandemic in Australia.
Answer in your book.
Activity 2

Outbreak Scenario

Apply outbreak investigation skills.

1 A school reports 15 students with vomiting and diarrhoea after a cafeteria lunch. Outline the first three steps an epidemiologist would take.
Answer in your book.
2 The sick students all ate chicken salad. Generate two hypotheses about the cause and explain how you would test them.
Answer in your book.
3 Why is it important for the health department to communicate findings quickly to the public during an outbreak?
Answer in your book.
Multiple Choice
Q

Test Your Understanding

RememberBand 3

1. What is epidemiology?

AThe study of individual patient treatments
BThe study of disease patterns in populations
CThe treatment of infectious diseases
DThe development of new vaccines
RememberBand 3

2. An outbreak is defined as:

AAny case of disease
BA disease occurring above the normal expected level
CA disease that spreads to other countries
DAny food poisoning event
RememberBand 3

3. Which Australian organisation coordinates national responses to communicable diseases?

AAIHW
BCDNA
CCSIRO
DNHMRC
UnderstandBand 4

4. Contact tracing is used to:

ADevelop new vaccines
BIdentify people who may have been exposed to a disease
CTreat infected patients
DCreate disease statistics
RememberBand 3

5. Ross River virus is mainly found in:

AMajor Australian cities
BRural and regional Australia
COnly in Tasmania
DOverseas only
Short Answer
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Short Answer Questions

UnderstandBand 4

1. Describe the role of epidemiologists in protecting public health. Include at least three specific tasks they perform. 4 MARKS

Answer in your book.
UnderstandBand 4

2. Explain why disease surveillance is important for Australia, using specific examples of diseases that are monitored. 4 MARKS

Answer in your book.
EvaluateBand 5

3. The Japanese encephalitis virus appeared in southern Australia for the first time in 2022. Evaluate how climate change might affect the spread of vector-borne diseases in Australia in the future. 4 MARKS

Answer in your book.

Revisit Your Thinking

Go back to your Think First answer. Has your understanding changed?

Update your thinking in your book.

Answers

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MCQ 1

B — Epidemiology is the study of patterns, causes, and effects of disease in populations, not individual treatments.

MCQ 2

B — An outbreak occurs when there are more cases of a disease than would normally be expected in a community or region.

MCQ 3

B — The Communicable Diseases Network Australia (CDNA) coordinates national responses to communicable disease threats.

MCQ 4

B — Contact tracing identifies people who may have been exposed to an infected person so they can be tested, treated, or isolated.

MCQ 5

B — Ross River virus is mainly found in rural and regional Australia, transmitted by mosquitoes that thrive in wet environments.

Short Answer 1

Model answer: Epidemiologists protect public health in several ways. First, they track disease trends by collecting and analysing data on diseases across populations, identifying patterns and changes over time. Second, they investigate outbreaks by finding the source of disease clusters, identifying how the disease spreads, and determining who is at risk. Third, they design prevention programs based on data, such as recommending vaccination campaigns or issuing public health warnings. They also analyse the effectiveness of interventions and communicate findings to health authorities and the public.

Short Answer 2

Model answer: Disease surveillance is essential for Australia because it enables early detection of outbreaks, guides public health policy, and protects the population. The National Notifiable Diseases Surveillance System (NNDSS) tracks about 70 diseases. For example, influenza surveillance tracks seasonal patterns and identifies unusually severe strains, triggering vaccination campaigns. Foodborne illness surveillance through OzFoodNet detects outbreaks of Salmonella and Campylobacter, leading to food recalls and improved safety standards. COVID-19 surveillance provided real-time data that guided lockdown decisions, border closures, and vaccination priorities. Without surveillance, outbreaks would go undetected until they became widespread.

Short Answer 3

Model answer: Climate change is likely to increase the spread of vector-borne diseases in Australia. Warmer temperatures allow mosquitoes to survive in regions that were previously too cold, potentially expanding the range of diseases like dengue fever, Japanese encephalitis, and Ross River virus southward. Increased rainfall and flooding create more breeding sites for mosquitoes. The 2022 Japanese encephalitis outbreak in southern states demonstrated this trend. Additionally, warmer temperatures can speed up pathogen replication inside mosquitoes, making transmission more efficient. Australia will need enhanced surveillance, expanded vaccination programs, and improved mosquito control to adapt to these changes. International cooperation is also essential, as disease vectors do not respect borders.

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Lesson Game

Outbreak Investigator

Solve a disease outbreak! Analyse data, trace contacts, and identify the source before the outbreak spreads further.

Mark lesson as complete

Tick when you have finished all activities and checked your answers.

Unit 1 overview · Science subject page