# Pathogens and Disease
Pathogens are microorganisms that cause disease. They include bacteria, viruses, fungi, and protists. Understanding how they spread and the diseases they cause is essential for GCSE Biology.
1. Types of Pathogens
| Type | How They Cause Disease | Example Disease |
|---|---|---|
| Bacteria | Produce toxins; damage cells | Salmonella, gonorrhoea |
| Viruses | Invade cells, replicate, burst out | Measles, HIV, TMV |
| Fungi | Hyphae penetrate tissues | Athlete's foot, rose black spot |
| Protists | Often spread by vectors | Malaria (mosquito vector) |
2. How Pathogens Spread
| Method | Examples |
|---|---|
| Airborne (droplets) | Measles, flu |
| Direct contact | Athlete's foot, STIs |
| Water contamination | Cholera |
| Vectors (organisms) | Malaria (mosquito) |
| Contaminated food | Salmonella |
3. Key Diseases
Measles (Virus)
- Spread: airborne droplets
- Symptoms: fever, red skin rash
- Prevention: MMR vaccination
- Complications: can be fatal
HIV (Virus)
- Spread: sexual contact, shared needles, blood
- Attacks immune system → AIDS
- Treatment: antiretroviral drugs (not a cure)
Salmonella (Bacterium)
- Spread: contaminated food (undercooked chicken, eggs)
- Symptoms: fever, vomiting, diarrhoea
- Prevention: proper food hygiene; poultry vaccination
Gonorrhoea (Bacterium)
- Spread: sexual contact
- Symptoms: thick discharge, pain urinating
- Treatment: antibiotics (increasing resistance is a concern)
- Prevention: barrier contraception
Malaria (Protist)
- Spread: mosquito vector
- Symptoms: recurring fever
- Prevention: mosquito nets, insecticides
Rose Black Spot (Fungus)
- Spread: wind and water
- Symptoms: black spots on leaves; reduces photosynthesis
- Treatment: fungicides; remove infected leaves
4. Preventing Spread
- Hygiene: handwashing, food preparation
- Vaccination
- Isolation of infected individuals
- Barrier methods (sexual health)
- Vector control (nets, insecticides)
5. Practice Questions
- Name the four types of pathogen.
- How is malaria spread and prevented?
- Compare how bacteria and viruses cause disease.
- Why is antibiotic resistance in gonorrhoea a concern?
- Describe three ways to reduce the spread of infectious diseases.
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Summary
- Pathogens: bacteria (toxins), viruses (cell invasion), fungi (hyphae), protists (vectors)
- Spread: air, contact, water, vectors, food
- Prevention: hygiene, vaccination, isolation, vector control
- Antibiotic resistance is a growing problem