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NSWBiologySyllabus dot point

Inquiry Question 3: How can the spread of infectious diseases be controlled?

Investigate and assess the effectiveness of historical and contemporary methods of prevention and control of infectious disease, including local, regional and global strategies (hygiene, quarantine, vaccination and public health campaigns)

A focused answer to the HSC Biology Module 7 dot point on disease control strategies. Covers hygiene, quarantine, vaccination programs, public health campaigns, and the role of the WHO, with named examples at each scale and a frank assessment of effectiveness.

Generated by Claude Opus 4.88 min answer

Reviewed by: AI editorial process; not yet individually human-reviewed

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  1. What this dot point is asking
  2. The answer
  3. Examples in context
  4. Try this

What this dot point is asking

NESA wants you to identify and evaluate strategies used to control infectious disease at local, regional and global scales. You must cover hygiene, quarantine, vaccination and public health campaigns, and assess their effectiveness with named examples. This dot point is examined in 6 to 9 mark extended responses.

The answer

Controlling infectious disease requires coordinated action at three scales: local (individual and community), regional (state or national) and global (international agencies). Strategies overlap in scale but differ in scope.

Local strategies

These target individuals and immediate communities.

Hygiene
Handwashing with soap, food preparation hygiene, surface cleaning and personal hygiene reduce pathogen transfer. Handwashing alone reduces respiratory and diarrhoeal disease by an estimated 20 to 40 per cent.
Personal protective equipment
Masks, gloves and gowns reduce transmission in clinical and community settings. N95 respirators are effective against airborne pathogens such as tuberculosis and SARS-CoV-2.
Case isolation
Symptomatic individuals stay home or are admitted to negative-pressure isolation wards.
School and workplace exclusion
Children with measles, chickenpox or whooping cough are excluded until non-infectious.

Regional strategies

These coordinate responses at state or national level.

Quarantine
Asymptomatic individuals who may have been exposed are isolated for the incubation period. Australia has used quarantine since federation, and operated hotel quarantine for international arrivals during the COVID-19 pandemic.
Contact tracing
Public health teams identify people who had contact with a confirmed case and monitor or isolate them. This was central to the 2003 SARS response and the early COVID-19 response.
Vaccination programs
National Immunisation Programs schedule vaccines from infancy through adulthood. The Australian National Immunisation Program includes vaccines against measles, mumps, rubella, pertussis, polio, hepatitis B, HPV and influenza.
Vector control
Mosquito control through breeding-site reduction, insecticide spraying and biological controls. Wolbachia-infected Aedes mosquitoes reduce dengue transmission in Far North Queensland.
Public health campaigns
Government education campaigns promote hygiene, vaccination, safe sex and other prevention behaviours. Australia's "Slip, Slop, Slap" and "Grim Reaper" (HIV awareness) are classic examples.

Global strategies

International coordination is led primarily by the World Health Organization (WHO).

International surveillance
The Global Influenza Surveillance and Response System tracks flu strains across 110 countries each year to determine vaccine composition. The WHO can declare a Public Health Emergency of International Concern (PHEIC).
Coordinated vaccination campaigns
Smallpox eradication (declared 1980) was the result of WHO-led ring vaccination over two decades. Polio eradication efforts continue, and wild polio now circulates in only Afghanistan and Pakistan.
Equitable access
Programs like Gavi, the Vaccine Alliance, and COVAX fund vaccine distribution to low and middle-income countries.
International Health Regulations
A binding treaty requires WHO member states to report public health emergencies and limit cross-border transmission.

Assessing effectiveness

Strategy Strengths Limitations
Hygiene Cheap, universal Requires sustained behaviour change
Quarantine Delays spread, buys time Economically and socially costly
Vaccination Prevents disease, builds herd immunity Vaccine hesitancy, cold chain logistics, no vaccine for many pathogens
Public health campaigns Shift long-term behaviour Slow, often contested
Global coordination Eradication possible (smallpox) Politically fragile, funding gaps

Most effective long-term strategy: vaccination, where a safe and effective vaccine exists.

Most effective short-term strategy: quarantine plus contact tracing, before vaccines are available.

Examples in context

Example 1. NSW COVID-19 contact tracing in 2020-2021. When SARS-CoV-2 cases were detected in the Northern Beaches Avalon cluster in December 2020, NSW Health's Public Health Response Branch deployed a contact tracing model widely held up as world-leading. Each confirmed case was interviewed within 24 hours to identify close and casual contacts; QR code check-ins at hospitality venues allowed automatic notification to thousands of patrons. Genomic sequencing at NSW Health Pathology linked cases by single nucleotide differences in the viral genome, identifying separate transmission chains. The cluster was contained to 151 cases by January 2021. The integration of local (testing centres), regional (state-wide tracing) and contact-tracing technology illustrates the layered nature of modern outbreak response.

Example 2. Smallpox eradication and the WHO ring-vaccination strategy. WHO declared smallpox eradicated globally in 1980, the only human disease ever eradicated. The campaign succeeded not because every person was vaccinated but because of ring vaccination: when a case was reported in a village (often in India or Ethiopia), local teams traced and vaccinated everyone in the immediate community within 48 hours, creating a barrier that prevented onward spread. Australian doctors including Frank Fenner played central roles in the WHO eradication committee. The strategy worked because smallpox has no animal reservoir, a long enough incubation period for contact tracing, a recognisable rash, and an effective single-dose vaccine. These conditions explain why the same model has not yet eradicated measles or polio.

Try this

Q1. Identify one local, one regional and one global strategy used to limit the spread of infectious disease, with an example of each. [3 marks]

  • Cue. Local: hand hygiene in NSW hospitals. Regional: state vaccination program (MMR in NSW). Global: WHO smallpox eradication via ring vaccination.

Q2. During a disease outbreak with R0 = 3, the introduction of mask-wearing reduces transmission by 40 percent. Calculate the effective reproduction number after intervention and predict whether the outbreak will continue. [3 marks]

  • Cue. R_eff = 3 by (1 - 0.4) = 1.8. Still above 1, so outbreak continues but more slowly; additional measures needed.

Q3. Evaluate the role of public health campaigns in controlling infectious disease. (a) Identify one Australian campaign. (b) Describe two channels through which it operated. (c) Justify whether public health campaigns are more effective than mandatory measures. [1+2+3 marks]

  • Cue. (a) NSW SunSmart, AIDS "Grim Reaper", COVID-19 "Stay Home" campaigns. (b) TV, social media, school programs, GP networks. (c) Behaviour change works long-term; mandates ensure compliance for high-risk situations but can erode trust.

Exam-style practice questions

Practice questions written in the style of NESA exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.

2025 HSC4 marksIn June 2022 the Varroa mite (an external parasite of honey bees) was detected for the first time in Australia at the Port of Newcastle and then spread to surrounding areas. Explain TWO procedures that could have been employed to prevent the spread of the Varroa mite in honey bees.
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Full marks (4) require explaining two prevention procedures (cause → effect). Sample answers from the guidelines:

  • Early identification/surveillance of infestation allows early detection and isolation of infected bee populations, stopping them spreading to healthy bees.
  • Destroying infected hives kills the mites and infected bees, preventing spread to healthy hives.

Other accepted: regular monitoring of colonies; minimising exposure by washing/disinfecting equipment; movement controls/quarantine zones. Marks scale: 3 for explaining one (or describing two), 2 for outlining two. Marker feedback: give procedures specific to this stimulus with added explanatory detail, not generic measures.

2023 HSC3 marksScientists investigated whether wearing clean clothing reduces malaria transmission, using containers of infected and uninfected mosquitoes with worn vs clean clothing (assume infected mosquitoes that land on clothing transmit malaria). Across repeated trials, mosquitoes landed far more often on worn clothing, and infected mosquitoes landed about three times as often as uninfected ones. Justify a suitable conclusion for this investigation.
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3 marks for a conclusion justified with the data. Sample answer: wearing clean clothing would reduce the transmission of malaria, because mosquitoes land on clean clothing on average fewer times than on worn clothing. Infected mosquitoes landed on clothing about three times as often as uninfected mosquitoes, and infected mosquitoes can only pass on infection if they land on and bite a host — so fewer landings on clean clothing means fewer opportunities for transmission. 2 marks for a conclusion with limited justification. Marker feedback: link the conclusion back to the aim and interpret the quantitative significance of the results.

2020 HSC3 marksCholera is an acute diarrhoeal infection caused by the bacterium Vibrio cholerae; humans are infected by consuming food or water contaminated with the bacterium. Outline THREE strategies that could prevent the spread of cholera.
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3 marks for outlining three prevention strategies (each linked to how it works). Sample answer: washing hands after using the toilet removes bacteria from the skin; purifying drinking water kills the bacteria present in water; proper disposal of sewage stops people being exposed to the bacteria. Each strategy targets the faecal–oral transmission of V. cholerae. 2 marks for three identified or two outlined. Marker feedback: give cholera-specific prevention strategies linked to their purpose, and focus on prevention of spread (not treatment of patients).

2019 HSC7 marksDengue fever (a virus spread by Aedes mosquitoes) and malaria (a single-celled organism spread by Anopheles mosquitoes) are mosquito-borne. A table shows global malaria data 1900–2010 (falling number of countries with cases but a rising population at risk) and maps show dengue distribution expanding from 1950 to 2010. Analyse factors that could have contributed to the change in global distribution of both dengue fever and malaria over the last 100 years. Support your answer with reference to the data provided.
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Top band (7) needs a thorough, data-linked analysis of multiple factors. Key points from the guidelines:

  • Both diseases depend on mosquito vectors; increased air travel lets infected people and vectors spread worldwide, and the rising global population (shown in the table) increases host density. Urbanisation creates new mosquito habitats — helping explain dengue's expanded distribution and malaria's growing population at risk.
  • Yet the number of countries with malaria has shrunk, suggesting the malaria vector has been contained — e.g. by pesticide spraying of water bodies and quarantine to stop mosquitoes establishing in new areas.
  • Medical advances (vaccines, antimalarial/antiviral drugs) have contained malaria more effectively than dengue; suitable dengue vaccines/drugs may be lacking, or the virus may evolve quickly, so dengue keeps spreading.

Marker feedback: identify multiple factors, support the analysis with the data, and use precise terms (incidence, distribution).

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