Pathogens and Disease

A comprehensive understanding of the causes and transmission of infectious diseases is essential in biology. Pathogens invade hosts, resulting in various illnesses. This revision note examines the different types of pathogens, their transmission methods, and strategies for controlling them.

Introduction to Pathogens and Disease

Pathogens: Organisms responsible for invading hosts and causing illness. They are integral to the development of diseases.

• Examples include bacteria that cause strep throat or fungi that lead to athlete's foot.
• Role in Disease: Affect humans, plants, and animals, presenting a variety of symptoms.
• Types of Infectious Diseases: Tuberculosis (bacterial), influenza (viral), malaria (caused by protozoa).

Types of Pathogens

Microorganisms

• Bacteria: Single-celled organisms responsible for infections, such as Staphylococcus. Diagram
• Fungi: Such as yeasts leading to skin infections. [Diagram of pathogen structure.]
• Protozoa: For instance, Plasmodium responsible for malaria.
• Viruses: Non-cellular entities, like influenza, spread via droplets. Virus lifecycle diagram.

Macroorganisms

• Parasitic Worms: Such as tapeworms that interfere with nutrient absorption. Parasite diagram.
• Arthropods: Vectors like ticks that transmit Lyme disease. Role of arthropods diagram.

Non-cellular Pathogens

• Prions: Infectious proteins causing disorders such as Creutzfeldt-Jakob disease. Diagram

Introduction to Disease Transmission

Understanding disease transmission is crucial for maintaining public health.

Transmission

Refers to the spread of a pathogen from one host to another.

• Direct Contact Transmission: Occurs through physical contact.
  • Example: HIV/AIDS is transmitted via blood or semen.
    Preventive measures, like condom use, are essential
    .
  • Example: Tuberculosis spreads through inhalation of aerosols.
• Indirect Contact Transmission: Involves contact with surfaces or airborne particles.
• Vector Transmission: Involves vectors such as mosquitoes transmitting malaria.

Transmission Models and Epidemics

Models are used to predict disease spread scenarios.

Epidemic

An epidemic is a rapid increase in the occurrence of a disease in a localised area.

• Epidemics vs Pandemics: Epidemics are localised outbreaks, whereas pandemics involve global spread.
• Example: The 2014-16 Ebola outbreak was an epidemic.

Historical Epidemic Cases

1918 Influenza

• Impacted one-third of the global population and led to advancements in health responses.

COVID-19

• Responses included lockdowns and vaccinations, highlighting the necessity for international collaboration.

Preventive Measures

Bacterial Infections

• Antibiotics: Target bacteria; preventing resistance is vital.
• Public Health Initiatives: Clean water and sanitation reduce infection rates.

Viral Infections

• Vaccination: For instance, the MMR vaccine enhances herd immunity.