How do viruses cause disease?

Viruses are not cells; they are tiny particles that invade host cells. Once inside, they hijack the cell's machinery to replicate, producing many new viruses. This damages or kills the host cell, leading to symptoms. For example, HIV infects T-helper cells, weakening the immune system.

What is the difference between an epidemic and a pandemic?

An epidemic is a sudden increase in cases of a disease in a specific region or population. A pandemic is an epidemic that spreads across multiple countries or continents, affecting a large number of people. For example, the 1918 flu was a pandemic, while a localised cholera outbreak is an epidemic.

Why can't we cure the common cold with antibiotics?

The common cold is caused by viruses (e.g., rhinoviruses), not bacteria. Antibiotics target bacterial cell walls or protein synthesis, which viruses lack. Using antibiotics for colds is ineffective and contributes to antibiotic resistance.

How does a vaccine work?

A vaccine contains a weakened or dead form of a pathogen. When injected, it stimulates the immune system to produce antibodies and memory cells. If the real pathogen later infects the body, memory cells quickly produce antibodies, preventing illness. This is called active immunity.

What is a vector in disease transmission?

A vector is an organism that transmits a pathogen from one host to another without getting the disease itself. For example, mosquitoes are vectors for malaria (caused by the protist Plasmodium). They pick up the pathogen from an infected person and pass it to a healthy person through a bite.

How can we prevent the spread of communicable diseases?

Prevention methods include: good hygiene (hand washing, covering coughs), safe food and water (cooking, chlorination), using barriers (condoms for STIs), controlling vectors (insecticides, bed nets), vaccination, and isolating infected individuals. Each method targets a specific transmission route.

Communicable disease

WJEC

GCSE

This topic explores the transmission, prevention, and treatment of communicable diseases caused by viruses, bacteria, protists, and fungi in humans and plants. It covers the human immune system's non-specific and specific defence mechanisms, the role of monoclonal antibodies, and the development of medicines including vaccines and antibiotics.

Objectives

Exam Tips

Pitfalls

Key Terms

Mark Points

Topic Overview

Communicable diseases are illnesses caused by pathogens such as bacteria, viruses, fungi, and protists. These diseases can be transmitted directly (e.g., through touch, droplets, or bodily fluids) or indirectly (e.g., via contaminated food, water, or vectors like mosquitoes). Understanding how pathogens spread and how the body defends itself is crucial for preventing outbreaks and maintaining public health. In the WJEC GCSE Biology course, you will study specific examples like cholera, tuberculosis (TB), HIV/AIDS, and malaria, focusing on their causes, symptoms, transmission, and control measures.

This topic is vital because communicable diseases remain a leading cause of death globally, especially in developing countries. By learning about the life cycles of pathogens and the immune response, you will appreciate the importance of hygiene, vaccination, and antibiotics. The topic also connects to broader themes such as the impact of lifestyle factors on disease susceptibility and the role of science in medicine. Mastering this content will help you understand current health challenges like antibiotic resistance and pandemic preparedness.

Within the WJEC specification, communicable disease is part of the 'Health, Disease, and the Development of Medicines' unit. It builds on earlier work about cells and microorganisms, and links to topics like the immune system, monoclonal antibodies, and drug testing. You will need to recall specific examples and explain how different pathogens cause disease, how they are transmitted, and how we can prevent or treat them. This knowledge is not only examinable but also essential for informed citizenship.

Key Concepts

Core ideas you must understand for this topic

→Pathogens are microorganisms that cause disease; they include bacteria (e.g., cholera), viruses (e.g., HIV), fungi (e.g., athlete's foot), and protists (e.g., malaria). Each has a different structure and mode of action.
→Transmission can be direct (e.g., droplet infection from coughs/sneezes) or indirect (e.g., contaminated water or vectors like mosquitoes). Understanding transmission helps in designing control measures.
→The body has defence mechanisms: physical barriers (skin, mucus), chemical barriers (stomach acid, lysozyme), and the immune system (white blood cells that phagocytose pathogens, produce antibodies, and create memory cells).
→Vaccination involves introducing a weakened or dead pathogen to stimulate the immune system to produce memory cells, providing long-term immunity without causing disease.
→Antibiotics kill or inhibit bacteria, but they are ineffective against viruses. Overuse leads to antibiotic resistance, where bacteria evolve and survive treatment.

What You Need to Demonstrate

Key skills and knowledge for this topic

Means of disease transmission (contact, aerosol, body fluids, water, insects, contaminated food)
Specific diseases: HIV/AIDS, Chlamydia, Ash die back, Malaria
Non-specific human defences: skin barrier and blood clotting
Immune system: role of lymphocytes (antibodies/antitoxins) and phagocytes
Monoclonal antibody production and uses (diagnosis, tissue typing, malaria monitoring, cancer chemotherapy)
Plant physical defences: cellulose cell walls, leaf cuticle, hardened cells, stinging cells, trichomes
Plant chemical defences: enzymes and toxic chemicals
Vaccination mechanism: antigens stimulating antibody production

Marking Points

Key points examiners look for in your answers

Means of disease transmission (contact, aerosol, body fluids, water, insects, contaminated food)
Specific diseases: HIV/AIDS, Chlamydia, Ash die back, Malaria
Non-specific human defences: skin barrier and blood clotting
Immune system: role of lymphocytes (antibodies/antitoxins) and phagocytes
Monoclonal antibody production and uses (diagnosis, tissue typing, malaria monitoring, cancer chemotherapy)
Plant physical defences: cellulose cell walls, leaf cuticle, hardened cells, stinging cells, trichomes
Plant chemical defences: enzymes and toxic chemicals
Vaccination mechanism: antigens stimulating antibody production
Antibiotic function: killing or preventing growth of bacteria
Aseptic techniques for culturing microorganisms
Drug development stages: preclinical (cells, animals, volunteers) and clinical testing

Examiner Tips

Expert advice for maximising your marks

💡Use specific terminology for immune responses (e.g., antigen-specific antibodies)
💡When discussing drug development, always mention the distinction between preclinical and clinical testing
💡Be prepared to evaluate the social and ethical implications of vaccination and gene technology
💡Ensure you can describe the specific role of monoclonal antibodies in different medical contexts
💡Practice interpreting data related to antibiotic effectiveness and bacterial growth
💡When describing transmission, always specify the method (e.g., 'through contaminated water' for cholera) and include the term 'vector' for diseases like malaria. This shows precise knowledge.
💡For vaccination questions, use the phrase 'memory cells' to explain long-term immunity. Examiners look for this key term to award full marks.
💡In questions about antibiotic resistance, link to natural selection: bacteria with resistance genes survive and reproduce, passing on the resistance. This demonstrates understanding of evolution.

Common Mistakes

Pitfalls to avoid in your exam answers

Confusing the roles of lymphocytes and phagocytes
Assuming antibiotics are effective against viruses
Failing to distinguish between physical and chemical plant defences
Misunderstanding the role of antigens in vaccination
Inaccurate description of aseptic techniques during microbial culture
Misconception: Antibiotics can cure viral infections like the common cold. Correction: Antibiotics only work against bacteria, not viruses. Viral infections require antiviral drugs or the body's own immune response.
Misconception: Vaccines cause the disease they protect against. Correction: Vaccines contain weakened or dead pathogens that cannot cause disease in healthy individuals. They trigger an immune response without causing illness.
Misconception: All bacteria are harmful. Correction: Many bacteria are harmless or beneficial (e.g., gut flora). Only pathogenic bacteria cause disease.

Frequently Asked Questions

Common questions students ask about this topic

Before You Start

Prior knowledge that will help with this topic

•Cells and organisation: understanding that pathogens are living organisms with cellular structures (or acellular for viruses).
•Microorganisms: basic knowledge of bacteria and viruses as microscopic entities.
•Defence mechanisms: prior learning about the immune system (white blood cells, antibodies) is helpful.

Study Guide Available

Comprehensive revision notes & examples

Read Study Guide

Likely Command Words

How questions on this topic are typically asked

Describe

Explain

Discuss

Evaluate

Recall

Ready to test yourself?

Practice questions tailored to this topic

Communicable disease

Topic Overview

Key Concepts

What You Need to Demonstrate

Marking Points

Examiner Tips

Common Mistakes

Frequently Asked Questions

Before You Start

Study Guide Available

Likely Command Words

Ready to test yourself?

Related Topics in WJEC GCSE Biology

Biodiversity

Cell biology

Cell metabolism

Coordination and control

Topic Synopsis

Key Concepts & Core Principles

Exam Tips & Revision Strategies

Common Misconceptions & Mistakes to Avoid

Examiner Marking Points

Communicable disease

Topic Overview

Key Concepts

What You Need to Demonstrate

Marking Points

Examiner Tips

Common Mistakes

Frequently Asked Questions

How do viruses cause disease?

What is the difference between an epidemic and a pandemic?

Why can't we cure the common cold with antibiotics?

How does a vaccine work?

What is a vector in disease transmission?

How can we prevent the spread of communicable diseases?

Before You Start

Study Guide Available

Likely Command Words

Ready to test yourself?

Related Topics in WJEC GCSE Biology

Biodiversity

Cell biology

Cell metabolism

Coordination and control