MS

Basic Concepts

A. Communicable Diseases – an illness due to an infection agent or its toxic products which is transmitted directly or indirectly to a well person or animal or thru an agency of an intermediate of an animal host, vector of the inanimate environment

Contagious Disease vs. Infectious Disease

A. Contagious Disease – easily spread directly from person to person; all contagious diseases are infectious.

B. Infectious Disease – applied to diseases not transmitted by ordinary contact, but requires a direct inoculation of a break in the previously intact skin or mucus membrane

Factors Responsible For The Transmission of Infection

Causative or Etiologic Agent - mode of action of infectious agent

Reservoirs of Infection – living bodies that harbor, sustain, and maintain the growth and multiplication of infectious agent

Two Types of Reservoirs

A. Human Reservoir - main reservoirs of infection

1. Infected persons from whom the infectious agent is transmitted to another person

2. Frank or Typical – person who are obviously ill and manifest typical signs and symptoms

3. Subclinical – infected persons where the disease is so mild that signs and symptoms are inapparent; referred to as missed or abortive, ambulatory/ walking cases

4. Carriers – infected persons who do not manifest any recognizable signs and symptoms (Strictly speaking no disease but the most dangerous)

5. Contact – close association

6. Suspect – medical history reveals that he has the disease

B. Animal Reservoir

Mode of Transmissions

A. By Contact Transmission

1. Direct contact (person to person)

2. Indirect contact (usually thru an inanimate object)

3. Droplet contact (from coughing, sneezing, or talking)

B. By Vehicle Route (thru contaminated items)

1. Food – salmonellosis (poisoning)

2. Water – shigellosis

3. Drugs – bacteremia resulting from infusion of a contaminated product

4. Blood – hepatitis B

C. By Airborne Transmission

1. Droplet nuclei – residue of evaporated droplets that remain suspended in the air

2. Dust particle containing the infectious agent

3. Organisms hed into skin thru environment

D. By Vector Borne Transmission (via contaminated or infected arthropods such as flies, ticks, and others)

E. By Vertical Transmission (from the mother to the neonate, e.g., AIDS, Hepatitis B and C, Malaria, Syphilis)

Mode of Entry/ Portal of Exit

1. Respiratory Tract – most common

2. GI Tract – easiest way thru indirect contamination

3. Genitourinary

4. Direct infection of Skin / Mucus Membrane

5. Percutaneous Infection – infections, bites and stings

Susceptible Host–humans or animals that don’t have resistance to infection

Factors AFecting Entrance of Infection To The Body

1. Age, Sex, Genetic Constitution

2. Nutritional Status, Fitness, Environmental Factors

3. Absentor Abnormal Immunoglobulins

a. Immunoglobulin (Ig) – related proteins that act as antibodies

4. General Physical, Mental, and Emotional Health

5. Status of hematopoietic system, efficacy of reticuloendothelial system

a. Efficacy of Reticuloendothelial System (RES) – concerned with defense against microbial infections

6. Presence of underlying disease (DM, Leukemia)

7.Patients treated with radiation, chemotherapy, corticosteroids, and other immuno suppressive agents