Chapter 16: Disease and Epidemiology

epidemiology

the study of where and when diseases occur and how they are transmitted in populations

chain of infection

organism -> reservoir -> transmission -> susceptible host

john snow

mapped cholera in london

ignaz semmelweis

handwashing

florence nightingale

sanitation decreased the incidence of epidemic typhus

reproductive number

average number of people who will contract a disease from one infected individual

descriptive epidemiology

collection and analysis of data (snow)

analytical epidemiology

analyzes a particular disease to determine its probable cause or risk factors (nightingale)

experimental epidemiology

involves a hypothesis and controlled experiments (semmelweis)

clinical trial

test and control group

case reporting

enables researchers to establish the chain of transmission

morbidity

incidence of a specific notifiable disease

mortality

deaths from notifiable diseases

notifiable infectious disease

diseases in which physicians are required to report occurence

morbidity rate

number of people affected in relation to the total population in a given time period

mortality rate

number of deaths from a disease in relation to the total population in a given time

sporadic disease

disease that occurs only occasionally

endemic disease

disease constantly present in a population

epidemic disease

disease acquired by many people in a given area is a short time

pandemic disease

worldwide epidemic

incidence

number of people who develop a disease during a particular time period

prevalence

number of people who have a disease at a specified time, regardless of when it first appears

takes into account both old and new cases

prevalence vs incidence

prevalence- describes total number of active cases

incidence- refers to the number of new cases of a disease in that population

common-source epidemic

arises from contamination of water or food

host-to-host epidemics

disease shows a slow, progressive rise and a gradual decline

e.g. infleunza and chicken pox

global spread of hiv/aids

increased number of immunocompromised persons, allowing for reemergence of some infectious diseases once thought to be "under control"

susceptible to infection (M. tuberculosis)

disease tracking for epidemics

find the index case or patient zero (first person with the disease) and then identify all people who had contact with the individual

quarantine

applied to healthy people exposed to a disease during the incubation

limits movement of people

mystery of the microcephalic newborns

link zika virus, a positive-sense rna virus that normally causes benign, mosquito-transmitted disease in adults, to the development of microcephaly in zika virus-infected fetal brains