BIO 208 - Microbiology - Unit 4 -Lecture 21 - Disease ...



These notes should be reviewed prior to the class on Disease Transmission and Epidemiology. We will NOT go over this material in class, but it is essential for your understanding of what we will be covering in class.Medical Microbiology1. Disease Transmission and Epidemiology – Chapter 14Disease - change from a state of healtha. Terminology related to infectious diseasesEtiology – the cause of a diseaseEtiological agent – the microorganism that causes the disease (synonymous with pathogen)Pathogen – a microorganism that is capable of causing diseasePathology – the study of diseasePathogenesis – the manner in which a disease develops and progressesInfection – invasion or colonization of the body by a pathogenIncubation – the time interval between infection and the first appearance of signs and symptomsSymptom – A subjective indication of a disease (something you the patient experiences), such as feeling hot, tired, achy, nauseousSign – An objective finding, usually detected on physical examination, from a laboratory test, or x-ray (etc) that indicates the presence of abnormality or disease, such as elevated body temperature (fever), increased respiration rate, elevated white blood cell count, fluid in the lungs, etc.Epidemiology – the study of disease in populationsa. Terminology related to epidemiologyEndemic = disease that is constantly present in a population (e.g., measles)Epidemic = an unusually large number of cases (every winter we see an epidemic of Influenza)Outbreak = a cluster of cases in a short time period (currently, avian influenza in southeast Asia)Pandemic = an epidemic that spreads worldwide (what we fear may happen with avian influenza)b. Reservoirs - where pathogens persist, a continual source of the organism that can fuel casesi. human reservoirs of disease – the primary reservoir of most diseases of humans is the human body itselfsymptomatic – a person exhibiting signs and symptoms of disease and is capable of infecting othersEx. someone with norovirus gastroenteritis (nausea, vomiting)asymptomatic carriers – a person that is not exhibiting signs and symptoms, apparently healthy, but infected and infectious to others.Ex. people infected with gonorrhea or herpes may be asymptomatic but are still infectiousii. nonhuman reservoirs of diseasezoonoses - diseases of animals that can be transmitted to humansEx. rabies, salmonellosisiii. environmental reservoirssoil (botulism, tetanus), water (Legionnaire's, cholera), etciv. hospitals and hospital personnel as reservoirs, especially of antibiotic resistant microorganismsc. Transmission – how pathogens are spreadi. by contacta) direct contact – also called person-to-person contact- when 1 person physically touches anotherEx. touching (MRSA infections), sexual contact (STIs)b) indirect - via inanimate objects = fomites – some examples include door knobs, telephones, computer keyboards, tv remotes, etcEx. cold viruses and Influenzac) droplet transmission – in droplets coming from the respiratory system (sneezes, coughs)Ex. tuberculosis, Influenza, SARSii. by food, water, or fecal contaminated material (fecal-oral)gastrointestinal pathogens incl. waterborne pathogensingestioncross-contamination of food preparation materialsEx. salmonellosis, shigellosis, choleraiii. airborne (similar to droplet transmission)Ex. anthrax, histoplasmosisiv. by vectorsa) mechanical - vector transfers microbes from one host to another.Ex. housefly, fleasb) biological - vector is required in microbe's life cycleEx. mosquitoesv. nosocomial – acquired as a result of being hospitalized, from the hospital environment or contact with hospital personnel or other patients.Significant problem!!! 5-15% of all hospitalized patients will develop a nosocomial infection (2 million people per year U.S. and 20,000 deaths). ................
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