Epidemiology Midterm Study Guide Epidemiology the study of what is upon the people o Concerned with the incidence of disease in a population Population trends risk factors screening clinical trials interventions and treatment outcomes o Aims of Epi Describes Explains Predict Control population heath status distribution outcomes and rates disease patterns causes transmission Monitor Health Outcomes surveillance screening distribution of diseases prevention containment o Two Types Descriptive who what where when maps how much Analytic how and why testing hypothesis cause Public Health v Healthcare o Public Health focus on pop data from surveillance generate hypothesis analytic studies community intervention o Healthcare focus on one person date from medical history make differential diagnosis diagnostic studies medical treatment Communicable Disease can be transmitted from one human to another or from anicals to humans also known as infectious disease Non communicable Disease non infectious or transmissible among people Zoonosis transmissible from a vertebrate animal to man normally a disease of animals ex Swine flu o Spread when animals lick of bite vectors on animals sexual contact with animals meat or milk products animal feces Levels of Disease o Endemic within people A disease or condition that persists within a certain geographical area Baseline or expected level of disease not preferred level o Epidemic around people Widely and rapidly spreading disease Rise significantly above normal endemic level o Pandemic all people Widespread epidemic Effects several countries impacts large amounts of people Case person diagnosed with health related state o Primary case first disease case in population o Index case first case brought to attention can be different than primary case Case definition ensures consistent diagnosis must include o Personal information place information time information and clinical information o Broad definition in beginning so potential cases are not missed Carriers may not be identified spreads or harbors infectious agent can be sick or health ex Typhoid Mary healthy carrier Epi Triangle o Host any susceptible organism invaded by an infectious agent human host variation age sex ethnic group socioeconomic status etc Host factors personal behaviors smoking diet drinking etc and immunization status vaccinated or not o Agent what makes you sick the germ bacteria virus parasite etc o Environment physical climate biological source of food water and air social and cultural density crowding sanitation Chain of Infection o Agent resides in host Resorviors natural habitat in which agent lives grow and multiply Humans symptomatic and asymptomatic Animals or Environment o Portal of exit Path by which an agent leaves it source host Respiratory tract skin conjunctiva o Made of transmission Direct transmission direct contact touching droplet spread Ex Kissing biting sex Droplet spreading water from sneezing Indirect tranmission Airborne suspended tiny particles Vehicle borne food water blood tissues fomites doorknobs Vector borne bugs most common mechanical or malaria biological multiply and undergo changes o Portal of Entry Respiratory tract ingest dermal blood borne mucous membranes o Infects the new susceptible host Prevention Strategies o Primary prevention preventing the disease before it happens ex Hand washing condoms properly cooking food o Secondary prevention detecting and treating to lessen the impact disease is already out ex Antibiotics isoloation o Tertiary prevention prevention of disease progression rehabilitation recovery Non communicable disease prevention education eating exercise safe sex Data o Discrete having a fixed number of values Ex Marital status blood type yes no answers o Continuous having an infinite number of values Ex Height weight etc Levels of Measurements o Qualitative data discrete Nominal no order gender yes or no questions Ordinal order grades stages of disease low medium high o Quantitative data discrete or continuous Interval temp in Fahrenheit or Celsius Ratio 0 means absent number of children Central Tendency mean median mode John Snow o Studied the 1854 cholera pandemic in London o Conducted the first modern outbreak investigation o Charted frequency and distribution of the cholera outbreak o Laid groundwork for descriptive and analytic epi o Used systematic methods to determine a cause of cholera Typhoid Mary o Chronic carrier o People can be a form of transmission o Importance of keeping track of carriers Landmark Studies o Doll and Hill A preliminary report on smoking and carcinoma of the lung Conducted long before carcinogens in tobacco were identified Case control design used to study lung cancer and cigarette smoking in British physicians Findings dose response risk of death increase proportionate to the amount of cigarettes smoked heave smokers more likely to get lung cancer than non smokes higher death rates in smokers Vertical v Horizontal Tranmission o Vertical to offspring through sperm placenta milk or vaginal fluids o Horizontal from an infected individual to another Direct vector vehicle Pathogens organism that are capable of producing diease Classification of disease and health o Acute 3 months or less o Chronic more than three months Spectrum of Disease o Exposure pathological changes symptoms clinical illness recovery disability or death Incubation period time between exposure to an infectious agent and when clinical symptoms appear Latency period time between exposure to an infectious agent and when the host becomes infectious to others o Do not have to be the same as the incubation period Disease Surveillance Chain of Command o Ideal process Heath care providers report to local Health Department Local Health reports to State Health Department State Health reports voluntarily to Federal level CDC CDC publishes Mortality and Morbidity Weekly Report Underreporting Big Problem o Doctors don t know what to report o Assume someone else has reported o Unaware how to report o Time consuming o No monetary incentive if doctors report well dramatically influence public health can changed something from epidemic to endemic Quarantine v Isolation o Quarantine no herd immunity potentially exposed but do not need to be ill Ring immunity combines quarantine with herd immunity help eradicate smallpox o Isolation you are ill Immunity basic principles of vaccination o Protection from infectious disease o Usually indicated by the