MIC 205 1st Edition Lecture 17Outline of Last LectureI. Virusesa. Role in Cancer II. Infection and Infectious DiseasesOutline of Current Lecture III. Etiology and InfectionIV. Reservoirs of InfectionV. Manifestations of DiseaseVI. Stages of Infectious DiseasesVII. VirulenceCurrent Lecture Etiology- Study of the CAUSE of a particular diseaseo Germ theory- diseases are caused by infections of pathogenic microorganisms (Koch’s Postulates)- Infection- results when the pathogen has evaded the external defenses, multiplied, and become established in host organism- Contamination- the presence of microbes on/in body- Disease (morbidity)- disease results only if the invading pathogen ALTERS the normal functions of the bodyo Portals of microbial entry: mouth, nose, ears, cut, eyes, anything with a hole Vehicle: water, dust Vector: insects, rats, lice Contact: fist bumpo Portals of exit: any portal of entryReservoirs of Infection- Reservoirs- sites where pathogens are maintained as sources of infectiono Three types: Animals- Zoonoses- diseases naturally spread from animal to humanThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.o acquired through direct contact with animal or waste, eating it or blood sucking arthropods Human carriers- Infected individuals who don’t have symptoms of the disease but are infective Nonliving reservoirs- Ex: soil, water, foodManifestations of Disease- Symptoms- subjective qualities of a disease felt by the patiento Ex: how bad does it hurt, how do you feel,- Signs- observable measureable things of a disease, objectiveo Ex: swelling, lab test results, body temp- Syndrome- group of symptoms and signs that characterize a disease- Asymptomatic- don’t have symptoms or signs that can be measures to determine if you have the disease or infectionStages of Infectious Diseases- 5 stage sequence called disease process 1. Incubation period- so signs/symptoms2. Prodromal period- vague, general symptoms3. Illness- most severe signs and symptoms4. Decline- declining signs and symptoms5. Convalescence- no signs/symptoms- **Infectiousness depends on the virus or disease**Virulence Factors- Virulence- degree of pathogenicity as determined by presence of virulence factorso More factors possessed by a microbe the better it is to be a pathogen Factors:- Adhesion factors- Extracellular enzymes- Toxins- Antiphagocytic factorso Adhesion factors Adhere to host cells Required for establishing colonies and starting growtho Extracellular enzymes Secreted by the pathogens- Have functions that can help the pathogen maintain infection, invadefurther and avoid body defenses- Dissolve structural chemicals in bodyo Examples: Hyaluronidase (break down sugary coatings around cells, bacterial cells can separate epithelial cells)  Collagenase (break down collagen proteins in basement membranes and invade deeper tissues)o Toxins Chemicals produced by the pathogen Harms tissues or trigger host immune responses that cause damage- Toxemia refers to the toxins in the bloodstream that are carried beyond the site of infectiono Examples Exotoxins secreted outside where they are made (cytotoxin- chemicals harmful to the cells) Endotoxins- Lipid A o Antiphagocytic Factors Certain factors prevent phagocytosis by host’s phagocytic cells- Bacterial capsule (antiphagocytic factor)o Makes it difficult for the bacteria to be engulfedEpidemiology of a Pandemic- World Health Organization tracks the spread of new strains by:o Descriptively Locations of infection, time, patients Goal = identify the first case of the diseaseo Analytically The probable cause, mode of transmission, analyze data to create ways of preventiono Experimentally Testing a hypothesis on the cause of the disease Apply Koch’s postulates- Epidemic: localized outbreaks (one continent)- Pandemics: spread across multiple continents (goes global)Influenza Virus Structure- Envelope of an influenza virus contains 2 spikeso NA- breaks down mucus (opens door)o HA- allows influenza to bind to epithelial cells and triggers endocytosis (Entry)- Named off type of HA and NA present in envelopeo H1N1 = type 1 HA, type 1 NAo H5N1- bird flu, affects middle age individuals and young adultsTamiflu- Used sparingly, eventually the flu will become