Epidemiology and Disease Transmission PDF

**EPIDEMIOLOGY AND DISEASE TRANSMISSION** **FACTORS THAT CONTRIBUTE TO THE SPREAD OF DISEASE** - Virulence of pathogen - Susceptibility of the population - Lack of immunization - Inadequate sanitation procedures - Mode of transmission of the pathogen **RESERVOIRS OF INFECTION**- any...

**EPIDEMIOLOGY AND DISEASE TRANSMISSION** **FACTORS THAT CONTRIBUTE TO THE SPREAD OF DISEASE** - Virulence of pathogen - Susceptibility of the population - Lack of immunization - Inadequate sanitation procedures - Mode of transmission of the pathogen **RESERVOIRS OF INFECTION**- any site where the pathogen can multiply or merely survive until it is transferred to the host - Human reservoir - Animal reservoir - Inanimate reservoir **HUMAN RESERVOIR-** principal living reservoir of disease because many human pathogens are specie-specific. **CARRIER--** harbors the pathogen but have no signs and symptoms - **INCUBATORY CARRIER --** transmits the pathogen during the incubation period - **CONVALESCENT CARRIER --** transmit pathogen during convalescence or recovery period - **ACTIVE CARRIERS --** completely recovered from disease but continue to harbor the pathogen indefinitely - **PASSIVE CARRIERS --** carry the pathogen without ever having the disease **ANIMAL RESERVOIR** **ZOONOSES-** infectious diseases that humans acquire from animal sources **ROUTES:** - **DIRECT CONTACT --** with infected animal or with domestic pet waste - **INHALATION --** from contaminated hides, fur, feathers - **INGESTION --** contaminated food and water; consumption of infected animal products - **INJECTION OF THE PATHOGEN --** insect vector **INANIMATE (NON-LIVING RESERVOIR)** - **e.g.** air, soil, food, milk, water, and fomites **FOMITES --** contaminated materials**e.g.** clothing, bedding, urinals/bedpans, eating and drinking utensils **AIR --** contaminated by dust, smoke, and respiratory secretions of humans expelled into the air by breathing, blowing, sneezing, and coughing **MODE OF TRANMISSION:** **CONTACT TRANSMISSION-** spread of an agent of disease by direct, indirect or droplet transmission - **DIRECT CONTACT TRANSMISSION-** person to person transmission of an agent by physical contact (source to susceptible host) no intermediate host involved i.e. touching, kissing, sexual intercourse - **INDIRECT CONTACT TRANSMISSION**- from source to a non-living object to a susceptible host - **DROPLET TRANSMISSION-** Microbe spread in droplet nuclei that travels only a short distance (\ 1 meter from the reservoir to host **VECTOR TRANSMISSION-** animals that carry pathogens from one host to another **CONTROL OF EPIDEMIC DISEASE:** - Report cases of communicable diseases to proper agencies - Public health educationIdentification and elimination of reservoirs of infection - Isolated disease person - Participate in immunization program - Help to treat sick person **HUMAN MICROORGANISM INTERACTION** **SYMPTOMS (SUBJECTIVE) --** evidence of disease that is experienced or perceived; changes in the body function noted by patient but not apparent to an observer. **SIGN (OBJECTIVE) --** evidence of a disease the physician can observe and measure **SYNDROME --** a specific group of signs and symptoms that accompany a particular disease. **INCIDENCE --** number of people in a population who develop a disease during a particular time period. **PREVALENCE --** number of people in a population who develop a disease regardless of when it first appeared (both old and new cases) **DISEASE --** impairment in the performance of vital function **DISEASE CAN BE DUE TO THE FOLLOWING:** 1. **INFECTIOUS DISEASE**-- caused by the growth of pathogens. 2. **MALFUNCTION OF AN ORGAN-** e.g. hyperthyroidism 3. **VITAMIN DEFICIENCY -** e.g. scurvy 4. **CAUSED BY ALLERGIC RESPONSE-** e.g. asthma 5. **CAUSED BY UNCONTROLLED CELL GROWTH-** e.g. cancer **MEDICAL MICROBIOLOGY-** focuses on infectious diseases 1. Based on behavior within the host; 2. Based on occurrence of disease 3. Based on severity or duration of disease 4. Based on extent of affected host's body; 5. Based on state of host's resistance **BASED ON BEHAVIOR WITHIN THE HOST:** **1. COMMUNICABLE DISEASE --** direct or indirect transmission of disease from one host to another - **CONTAGIOUS DISEASE --** communicable disease that is easily transmitted from one person to another **2. NON-COMMUNICABLE DISEASE --** do not spread from one host/ person to another **BASED ON OCCURRENCE OF DISEASE:** 1. **SPORADIC DISEASE --** disease occurs only occasionally; controlled as a result of immunization and sanitation procedures (non-endemic) 2. **ENDEMIC DISEASE --** constantly present in a population or community usually involving only few people. 3. **EPIDEMIC DISEASE --** greater than normal number of cases in an area within a short period of time 4. **PANDEMIC DISEASE --** worldwide epidemic of a specific disease **e.g.** AIDS, influenza **BASED ON SEVERITY OR DURATION OF DISEASE:** 1. **ACUTE DISEASE** - develops rapidly (rapid onset) but lasts only a short time **e.g.** measles 2. **CHRONIC DISEASE --** develops more slowly (insidious onset); disease is likely to be continual or recurrent for long periods **e.g.** TB, leprosy **BASED ON EXTENT OF AFFECTED HOST'S BODY:** 1. **LOCAL INFECTION --** microbes invade a relatively small area of the body 2. **GENERALIZED (SYSTEMIC) INFECTION --** spread throughout the body or lymph 3. **FOCAL INFECTION --** local infection that enter the blood that spread to other parts **BASED ON STATE OF HOST'S RESISTANCE:** 1. **PRIMARY INFECTION --** acute infection that causes the initial illness 2. **SECONDARY INFECTION --** caused by an opportunistic pathogen after the primary infection has weakened the body's defenses 3. **SUBCLINICAL (INAPPARENT) INFECTION --** does not cause any noticeable illness **STAGES OF DISEASE:** 1. **INCUBATION PERIOD --** time interval between the initial infection and 1st appearance of any signs or symptoms 2. **PRODROMAL PERIOD -** early, mild symptoms of disease 3. **PERIOD OF ILLNESS --** progression of signs and symptoms; critical stage 4. **PERIOD OF DECLINE --** signs and symptoms subside; vulnerable to secondary infection 5. **PERIOD OF CONVALESCENCE --** recovery period **ISOLATION TECHNIQUES FOR THE LABORATORY WORKERS** **CARRIER --** a person who harbors an organism and has no symptoms or signs of disease, but is capable of spreading the organism to others. **FOMITES --** inanimate objects that may be contaminated with infectious organisms and may serve as a means of their transmission. **NOSOCOMIAL INFECTION-** infection acquired in a hospital or health care facility. **INFECTION --** a pathological condition caused by growth of microorganisms in the host **ISOLATION --** the practice of limiting the movement and social contact of a patient who is potentially infectious or who must be protected from exposure to infectious agents. **MICROORGANISM-** a single-celled microscopic organism. **NONPATHOGENIC-** not normally causing disease in a healthy individual **PATHOGEN-** an organism or agent capable of causing disease in a host **TYPES OF ISOLATION:** **CONTACT ISOLATION --** a type of isolation to prevent transmission of diseases spread by close or direct contact **RESPIRATORY ISOLATION-** a type of isolation to prevent transmission of organisms spread through the air over short distances **REVERSE/PROTECTIVE ISOLATION-** a type of isolation designed to protect highly susceptible patients from exposure to infectious agents; protective isolation **STRICT ISOLATION-** a type of isolation to prevent transmission of highly contagious or virulent infections **PROCEDURES FOR PERSONAL PROTECTION** - Handwashing - Masks - Gloves - Gowns **HANDWASHING-** is the most important procedure in isolation techniques, just as it is in maintaining safety in the laboratory. Proper handwashing should be the first and last step of all procedures. **Note:** Handwashing does not sterilize the hands, but removes surface contaminants, dead skin and surface organisms.