Disease and the Immune Response · Summer Term

Pathogens and Infection

Identifying the types of bacteria, viruses, and fungi that cause illness in humans.

About This Topic

Pathogens and Infection introduces students to the microscopic organisms that cause disease: bacteria, viruses, and fungi. In the 6th Year curriculum, students learn to distinguish between these groups based on their structure and reproduction methods. They explore how pathogens spread through populations and the various ways the body and society can prevent infection. This topic is more relevant than ever in a post-pandemic world and connects deeply to the NCCA's focus on public health and the 'Nature of Science.'

Students examine the life cycles of specific pathogens and the conditions that allow them to thrive. In Ireland, this includes looking at historical and modern health challenges. This topic particularly benefits from hands-on, student-centered approaches where students can physically model the patterns of disease transmission and participate in collaborative problem-solving to stop a 'simulated' outbreak.

Learning Objectives

• Compare and contrast the cellular structures and reproductive strategies of bacteria, viruses, and fungi.
• Explain the mechanisms by which pathogens spread within a human population, including direct contact, airborne transmission, and contaminated vectors.
• Analyze the factors that influence a host's susceptibility to infection, such as immune status and pre-existing conditions.
• Design a public health campaign poster illustrating at least three methods for preventing the transmission of common infectious diseases.
• Evaluate the effectiveness of different public health interventions, like vaccination and hand hygiene, in controlling disease outbreaks.

Before You Start

Cell Structure and Function

Why: Understanding basic cell biology is essential for differentiating between cellular pathogens like bacteria and acellular ones like viruses.

Introduction to Microorganisms

Why: Students need a foundational understanding of what microorganisms are and that some can be beneficial while others are harmful.

Key Vocabulary

Pathogen	A microorganism, such as a bacterium, virus, or fungus, that can cause disease.
Bacteria	Single-celled microorganisms that can live in many environments, some of which cause disease by releasing toxins or invading tissues.
Virus	Microscopic infectious agents that can only replicate inside the living cells of other organisms, often hijacking host cell machinery.
Fungi	A diverse group of organisms, including yeasts and molds, that can cause disease by infecting tissues or producing toxins.
Transmission	The process by which an infectious agent passes from one host to another, or from an environmental source to a host.

Active Learning Ideas

Simulation Game: The Outbreak Mystery

Students are given 'patient profiles' with symptoms and recent travel history. Working in groups as 'epidemiologists,' they must trace the source of the infection and identify whether the pathogen is likely a bacterium, virus, or fungus based on the evidence.

⏱ 50 min·Small Groups

Generate mission

Think-Pair-Share: Virus vs. Bacteria

Provide a list of characteristics (e.g., 'can be killed by antibiotics,' 'needs a host to reproduce,' 'has a cell wall'). Pairs must sort these into a Venn diagram to compare viruses and bacteria, then explain their choices to another pair.

⏱ 20 min·Pairs

Generate mission

Gallery Walk: Pathogen Profiles

Post 'Wanted' posters for different pathogens (e.g., Influenza, Athlete's Foot, Salmonella). Students move around the room to identify the mode of transmission (airborne, waterborne, contact) and the best prevention method for each.

⏱ 30 min·Small Groups

Generate mission

Real-World Connections

Public health officials at the Health Protection Surveillance Centre (HPSC) in Ireland track infectious disease outbreaks, such as seasonal influenza or norovirus, using epidemiological data to inform public health advice and interventions.

Microbiologists in pharmaceutical companies, like those in Dublin, research and develop new antiviral medications and vaccines to combat emerging infectious diseases and antibiotic-resistant bacteria.

Food safety inspectors in local authorities work to prevent the spread of foodborne illnesses caused by bacteria like Salmonella or E. coli, ensuring compliance with hygiene standards in restaurants and food production facilities.

Watch Out for These Misconceptions

Common Misconception

All bacteria are 'bad' and cause disease.

What to Teach Instead

Students often have a negative view of all microbes. Active learning that explores the 'human microbiome' or the role of bacteria in food production (like yogurt) helps them understand that the vast majority of bacteria are harmless or even beneficial.

Common Misconception

Viruses are just very small bacteria.

What to Teach Instead

Many students don't realize that viruses are not technically 'alive' because they cannot reproduce on their own. Peer-led comparison of cell structures helps clarify that viruses lack the machinery (like ribosomes) found in even the simplest bacteria.

Assessment Ideas

Quick Check

Present students with images of different microorganisms. Ask them to label each as bacteria, virus, or fungus and write one key characteristic that helped them identify it. For example: 'This is a virus because it shows no cellular structure and needs a host to replicate.'

Discussion Prompt

Pose the question: 'Why are some diseases, like the common cold, easily spread, while others, like tetanus, are less common in vaccinated populations?' Facilitate a class discussion focusing on modes of transmission, incubation periods, and the role of immunity.

Exit Ticket

Students respond to the prompt: 'Imagine you are advising a community on how to prevent a local outbreak of a new virus. List two specific actions people should take and explain why each action is effective.'

Frequently Asked Questions

What are the main differences between a virus and a bacterium?

Bacteria are single-celled living organisms that can reproduce on their own and can often be treated with antibiotics. Viruses are much smaller, consist only of genetic material inside a protein coat, require a living host cell to reproduce, and are not affected by antibiotics.

How can active learning help students understand infection?

Infection is an invisible process. By using 'glow-germ' simulations to track hand-shaking or 'outbreak' role-plays to trace transmission, students see how easily pathogens spread. This makes the abstract concepts of 'vectors' and 'modes of transmission' concrete and emphasizes the importance of hygiene and public health measures.

What is a 'vector' in disease transmission?

A vector is an organism that does not cause disease itself but spreads infection by conveying pathogens from one host to another. Common examples include mosquitoes (malaria), ticks (Lyme disease), and even houseflies.

Why can't we use antibiotics to treat the flu?

The flu is caused by a virus. Antibiotics are designed to target specific structures or processes in bacteria (like cell wall synthesis) that viruses simply do not have. Using antibiotics for viral infections is ineffective and contributes to the problem of antibiotic resistance.