MBI 131September 3, 2013Epidmiology: The Study of Disease, Injury, and Death in the CommunityHomework for Thursday: find and bring to class a news article that relates to some health organization (see organizations in chapter two in book). Somewhat current about an activity that that group has done. Epidemiology=population medicine. Epidemiologists concerned with the course of disease in a population. Collect information about disease status of a community (How many people are sick, who is sick, when did they become sick to see when the outbreak occurred and to see the susceptibility level, where do they live?)o Data can be used to prevent disease outbreaks (how does a disease spread, who gets what and when and how often, etc.?) or determine effectiveness of prevention effort Epidemiology is the study of distribution and determinants of health relatedstates or events in specified population Epidemic—unexpectedly large number of cases of an illness, specific health related behavior or event, in a particular population Endemic—disease that occurs regularly in a population as a matter of course. Can be seasonal (like the flu), rises and falls regularly. Or endemic to apopulation as that population grows and ages. Pandemic—outbreak over wide geographic area What does time vs numbers of cases tell you? If it is communicable or not.  Importance of rates—rates allow for comparison of outbreaks at different times or different placeso Cases are people afflictedo Rates are the number of events in a given population over a period of time or given point in time. We will study things like natality (birth), morbidity (sickness), mortality or fatality (death) rates.o Population at risks—those susceptible to a particular disease or condition. In our society this is babies and old people. Morbidity Rates:o Incidence rate is the number of new health related events or cases of a disease in a population exposed to that risk during a particular period of time, divided by total number in the same population. Tells the percentage chance of you getting it. Who has it and how often are they showing up on the radar? How many people should I expect to beafflicted?o Prevalence looks at the number of cases in a population. More like a ratio of how many are affected total.o Attack rate is the incidence rate calculated for a particular populationfor a single disease outbreak, expressed as a percentage. How often isit going to affect this population? How quickly is it going to spread? How many people has it spread to? Incidence rates important to study of acute diseases, who last three months or less and prevalence rates are for the study of chronic diseases, those who last longer than three months Incidence and prevalence rates expressed as crude or specific Crude rates are where the denominator includes the total population. Example—crude birth rate is the number of live births in a given year dividedby midyear population. Crude death rate is the number of deaths in a given year from all the causes, divided by midyear population.o Out of everyone, what are my chances? Age-adjusted rates—used to make comparisons of relative risks across groups and over time when groups differ in age structure Specific rates—measure morbidity and mortality for particular populations or diseases. The case fatality rate is the percentage of cases in a particular disease that resulted in death. The proportional mortality ratio is the percentage of overall mortality in a population that is attributable to a particular disease Reporting of deaths, birth, and diseases—physicians, clinics, and hospitalsare required to report births, deaths, and notifiable diseases. Notifiable diseases are infectious diseases in which health officials request or require reporting. Diseases that can become epidemics or are worried to be extremely communicable. Because of this, health officials maintain weekly records. Mortality statistics are the most reliable measure of a population’s health status and is easier to track death than illness. Life expectancy is the averagenumber of years a person from a specific cohort is projected to live from a given point of time. Years of potential life lost (YPLL) is he number of years lost when death occurs before one’s life expectancy.o Various valid sources have specific values and usefulness to those in public health. Example—US Censuso Taken every 10 years, is the enumeration of the population and is more complex now that ever before. It gathers data on demographics: race, age, income, employment, education, and other social