Biology.illinoisstate.edu
BSC 260
Epidemiology and Transmission
4/4/12
Epidemiology-the study of occurrence, distribution, and determinants of disease in a population
Identify trends and link to mechanisms
Often tied to public health on action side of process
Definitions:
Epidemic-disease that occurs in large number of people at one time
Pandemic-epidemic that is spread worldwide
Endemic-typically found in a population usually at a low frequency
Outbreak-the sudden increase in the number of cases of a disease
Mortality-the incidence of death in a population
Morbidity-the incidence of sickness or injury in a population
Resevoirs-sites or organisms in which pathogens may remain from which to cause infection at a later time
Animals are common reservoir for human disease
Zoonotic disease when animals transmit to humans
Rabies
Transmission-pathogens are frequently grouped by their mode of transmission to host
Direct host-to-host transmission
Infected host transmits pathogen to new host
Flu, cold, stds
Indirect transmission
A vector acts to deliver the pathogen from host to new host
Pathogens are carried by someone or something that does not contract the disease
Arthropods (mosquitos, mites, ticks, fleas)
Water
Medical equipment
Vector borne diseases tend to be more severe since there is no need to keep previous host healthy enough to transmit pathogen
Transmission and symptoms-
Successful pathogens tend to manipulate the host immune system to increase the likelihood of transmission to new hosts
•respiratory pathogens cause coughing or sneezing
•water-borne pathogens cause diarrhea
•arthropod-borne pathogens often cause lethargy which allows bites by other insects
•STDs cause lesions on genitals which secrete pathogen during sex with new potential host
Transmission rate is linked to virulence of pathogens
Large population of naïve hosts result in high virulence over time
Population of resistant hosts leads to diminished virulence
Over time, the virulence of a pathogen should attenuate if new transmission mechanism is not present
Herd immunity-when a large enough percentage of the population is resistant to a pathogen that it becomes very unlikely that the sensitive members of the population will be exposed and contract the disease
About 85% of population with vaccinations
Diseases with variable transmission mechanisms: AIDS
In the US, AIDS is frequently a disease of men who have sex with men, and IV drug users
In Africa, AIDS is a disease of heterosexuals and infants of infected mothers
Nosocomial infections-acquired from hospital or clinic visit
Serious health problem
Wound infection, pneumonia, UTI, bloodstream infection
Pathogen is typically more virulent than one found outside of the hospital
Global health
In US 10% of deaths are associated with infectious disease
In Africa 52% of deaths are associated with infectious diseases
Standard of living, available medical care, climate, diet, etc. can all play a part in severity of infectious disase
................
................
In order to avoid copyright disputes, this page is only a partial summary.
To fulfill the demand for quickly locating and searching documents.
It is intelligent file search solution for home and business.