Epidemiology 1.pdf PDF

# Portal of Exit - A portal of exit is when an infectious agent can spread to a new host and survive in an external environment after leaving the human body until it finds a new host. - **Example:** the common cold. # Chain of Infection - **Source or Reservoir (1)**: Where infectious agents live an...

# Portal of Exit - A portal of exit is when an infectious agent can spread to a new host and survive in an external environment after leaving the human body until it finds a new host. - **Example:** the common cold. # Chain of Infection - **Source or Reservoir (1)**: Where infectious agents live and multiply. - **Modes of Transmission (2)**: How infectious agents are spread. - **Susceptible Host (3)**: A person who is at risk of getting sick from the infectious agent. ## Immunity - **Immunity** is when a person is resistant to an infectious agent due to the immune system. - **Immunization** is a process by which an individual resists and overcomes infection by acquiring resistance. - **Naturally acquired resistance** is when the body naturally possesses the power to resist some attacks of viruses. - **Artificially acquired resistance** is when an individual acquires resistance through immunization. - **Types of immunity:** (a) Active immunity, (b) Passive immunity. - **Active immunity:** An individual develops resistance through infection or vaccination. - Active immunity can be acquired in three ways: 1. Following a clinical infection (chicken pox, rubella). 2. Following a subclinical inapparent infection (polio, diptheria). 3. Following immunization with an antigen. - **Passive immunity:** An individual receives antibodies from another source, like a mother through breast milk. - **Examples of Passive Immunity:** 1. **Maternal antibodies:** A baby receives antibodies from the mother through the placenta or breast milk. 2. **Passive immunization:** Antibodies are transferred from an individual who has already developed immunity to an individual who hasn't. ## Immunizing Agents - An immunizing agent is a substance or organism that produces immunity when introduced into the body. - Immunizing agents are classified as vaccines, immunoglobulins, and antisera. ### Vaccines - **Vaccines** are biological substances designed to produce a specific protection against a disease. - **How vaccines work:** - Vaccine introduces an antigen into the body. - The body stimulates the formation of antibodies, and the individual develops active immunity. - **Types of vaccines:** live vaccines, killed vaccines, and toxoids. - **Live vaccines:** MMR (Measles, Mumps, and Rubella), OPV (Oral Polio Vaccine), Yellow Fever Vaccine, BCG vaccine (for Tuberculosis). - **Killed vaccines:** IPV (Inactivated Polio Vaccine), Hepatitis A Vaccine, Rabies Vaccine, Japanese Encephalitis Vaccine. - **Toxoids:** Diptheria and Tetanus vaccines. ### Immunoglobulins - **Immunoglobulins** are a type of large glycoprotein produced by B-cells of the immune system. - **Function of Immunoglobulins:** - They interact with specific antigens. - They defend the body against pathogens. - **Uses of Immunoglobulins:** - Diagnosis, treatment, and monitoring of diseases like cancer. - Low levels of immunoglobulins can indicate that the immune system is not working properly. ### Antisera - **Antisera** is blood serum containing antibodies obtained by the inoculation of animals. - **Use of Antisera:** - To provide passive immunity to a specific disease. - Antisera is generally harvested from animals and used for injection into another animal. ## Combined Vaccines - Combined vaccines include multiple immunizing agents in one vaccine to reduce the number of injections required for patients. - **Example**: DPT (Diptheria, Pertussis, Tetanus), DT (Diptheria, Tetanus), MMR (Measles, Mumps, Rubella). ## Hazards of Immunization - The term hypersensitivity (allergy) refers to the reaction that occurs when a foreign substance is introduced into the body. - **Types of Hypersensitivity:** 1. **Immediate or Antibody-mediated:** Caused by anaphylaxis, or an allergic reaction. 2. **Delayed or Cell-mediated:** Caused by allergies. - **Other hazards:** 1. **Faulty techniques:** Inadequate inactivation of the vaccine, overdose of vaccine, or incorrectly prepared and stored vaccine. 2. **Reactions inherent to inoculation:** Localized or generalized reactions like pain, swelling, redness at the site of injection. 3. **Other hazards:** Damages to the fetus, neurological disorders. - **Example:** Rubella vaccination can damage the fetus and cause neurological disorders. ## The Cold Chain - The cold chain system is a temperature-controlled supply chain for storing and transporting vaccines at low temperatures from the manufacturer to the person being immunized. - **Importance of the Cold Chain:** - Ensures the effectiveness of vaccines. - Prevents the loss of potency of vaccines due to heat or freezing. - **Equipment for the Cold Chain:** - Refrigerated production facilities: Maintain optimal temperatures during the manufacturing process. - Cold storage warehouses: Store perishable goods at specific temperatures to prevent spoilage. - Temperature-controlled transportation: Refrigerated trucks, containers, and other modes of transport are used to move vaccines while maintaining the desired temperature range. - Other equipment: Deep freezers, cold boxes, vaccine carriers, ice packs. ## Key Benefits of the Cold Chain - Preservation of product quality. - Reduction of food waste. - Improvement of safety and hygiene. - Enhanced patient satisfaction. - Economic growth. ## Challenges in the Cold Chain - Maintaining temperature control. - Infrastructure development. - Energy consumption. - Monitoring and traceability.