Infectious Diseases: Emergence, Spread, and Immunity

Emerging and Reemerging Diseases

Emerging diseases are caused by previously unknown germs. These germs may have been hidden or have mutated. An example is Ebola.

Reemerging diseases are those that reappeared after a period of decline. Examples include cholera, tuberculosis, dengue, and malaria.

Outbreaks and Spread

An epidemic outbreak is the rapid spread of an infectious disease affecting many people in a limited area and time.

A pandemic is an epidemic affecting many parts of the world.

Key Concepts

A syndrome refers to the complex and variable damage caused by infectious agents.

A reservoir is an animal that harbors infectious agents transmissible to humans, such as rodents.

A vector is an animal that transmits germs to a healthy person, such as mosquitoes.

Immunity is the ability to resist infectious diseases.

An antigen is a molecule that triggers an immune response.

Antibodies are proteins that bind to antigens and aid in their destruction.

Vaccination introduces a pathogen or part of it to stimulate the immune system.

Immune Response

1. A macrophage (phagocyte) engulfs a germ.

2. Part of the germ is presented on the macrophage's surface to lymphocytes.

3. The lymphocyte that can create effective antibodies is stimulated to grow.

4. B cells produce antibodies (humoral response).

5. T cells destroy infected cells (cellular response).

Other Concepts

Koch's Postulates

• The organism is present in all individuals with the disease.
• The microorganism can be isolated from the patient and cultured.
• The isolated organism should cause the same disease when introduced into another individual.
• The experimentally infected individual must contain the microorganism.

Antibiogram

Culturing pathogens to determine which treatment kills bacteria fastest.

Patent

Exclusive rights to market a drug for at least 20 years.

Generic Drug

A drug with the same composition, efficacy, safety, and quality as the original.