Understanding Infection and the Body's Response

What are Pathogens?

Pathogens are microorganisms that can cause disease. The main types are:

• Bacteria - Single-celled organisms that reproduce rapidly
• Viruses - Non-living particles that invade host cells
• Fungi - Multi-celled organisms like yeasts and molds
• Protists - Single-celled organisms like plasmodium (malaria)

How Pathogens Spread

Pathogens can spread in various ways:

• Direct contact with infected individuals or surfaces
• Through contaminated food, water, or animal vectors
• Via airborne droplets from coughs or sneezes

The Body's Defence Mechanisms

The body has multiple defences against pathogens:

1. Physical Barriers - Skin, mucus membranes block entry
2. Immune System
   • White blood cells destroy pathogens by phagocytosis
   • Lymphocytes produce antibodies that bind to antigens
   • Memory cells retain pathogen information for future attacks

Vaccination and Antibiotic Resistance

Vaccinations expose the body to inactive forms of a pathogen, allowing it to develop immunity safely. However, overuse of antibiotics has led to antibiotic resistance in bacteria, making infections harder to treat.

Plant Diseases Example

Plants also face pathogens like fungi, bacteria, and viruses that can cause diseases like blight, rusts, and mosaic viruses. These can devastate crop yields.

By understanding pathogens and the immune system, we can develop better prevention and treatment strategies against infectious diseases.