Types of Pathogens

Types of Pathogens

What Are Pathogens?

Pathogens are microorganisms that cause disease. They can spread between organisms and lead to communicable diseases.

💡 Key Concept: The four main types of pathogens are bacteria, viruses, fungi, and protists.

The Four Types of Pathogens

Pathogen Type

Size

How They Cause Disease

Examples

Bacteria🦠

Small cells

Release toxins that damage cells

Salmonella (food poisoning), Tuberculosis

Viruses🧬

Smaller than bacteria

Invade host cells and reproduce inside, destroying them

HIV, Influenza, Measles

Fungi 🍄

Some are single-celled, others have a body (hyphae)

Grow on surfaces, spread using spores

Athlete’s foot, Rose black spot

Protists🦟

Single-celled organisms

Carried by vectors (e.g., mosquitoes), infect cells

Malaria

How Do Pathogens Spread?

Method of Transmission

Example Disease

Airborne droplets (coughing/sneezing)

Influenza, Measles

Contaminated water

Cholera

Direct skin contact

Athlete’s foot

Food contamination

Salmonella

Vector transmission (e.g., insects)

Malaria (mosquitoes)

💡 Key Fact: Viruses are not living organisms because they need a host cell to reproduce.

Pathogen Case Studies

1️⃣ Bacteria: Salmonella (Food Poisoning)

🔹 Cause: Eating contaminated food.
🔹 Symptoms: Fever, vomiting, diarrhoea.
🔹 Prevention: Cooking food properly, good hygiene.

2️⃣ Virus: HIV (Human Immunodeficiency Virus)

🔹 Cause: Spread by bodily fluids (e.g., unprotected sex, shared needles).
🔹 Effects: Attacks the immune system, leading to AIDS.
🔹 Prevention: Safe sex, not sharing needles, antiviral drugs.

3️⃣ Protist: Malaria

🔹 Cause: Spread by mosquito bites.
🔹 Symptoms: Fever, chills, sweating.
🔹 Prevention: Mosquito nets, insect repellent, antimalarial drugs.

Questions 

  1. Name the four types of pathogens.
  2. How do viruses cause disease?
  3. Which pathogen spreads via spores?
  4. How is malaria transmitted?
  5. What is a symptom of Salmonella infection?

Summary 

  • Pathogens are microorganisms that cause disease.
  • The four types are bacteria, viruses, fungi, and protists.
  • Pathogens spread through air, water, food, and vectors.
  • Examples: Salmonella (bacteria), HIV (virus), Malaria (protist), Athlete’s Foot (fungi).