Lecture 36/37/38 Epidemiology Flashcards
Epidemiology
the study of the occurrence, distribution, and determinants of health and disease in a population and the application of this study in the control of health problems
What do epidemiologists do?
trace the spread of disease to identify its origin and mode of transmission
What types of data do epidemiologists collect on populations?
demographics, symptoms, history, animal vector data, medical records, etc
When did epidemiology start?
mid-1880s
Ignaz Semmelweis
“Savior of Mothers”; implemented handwashing wtih chlorinated lime solutions
Florence Nightingale
nurse and statistician; sent to Ukraine to report conditions of infection during the war
John Snow
“Father of Epidemiology”; british physician in the 1850s that pioneered epidemiological investigations and disease mapping
Why were Nightingale’s Rose diagrams significant?
provided a visual that was easier to understand than charts
Epidemic
when as disease occurs in an unusually high number of individuals in a population at the same time
What did John Snow do in the 1850s?
traced the source of an outbreak of Cholera to a water pump on Broad St.
Where there other people investigating this cholera outbreak at the same time?
Yes; for example, Edmund Cooper and the British Empire
Endemic
normal rates of disease that is expected in a population
Endemic Disease
constantly present, occurs at a steady low frequency with predictable changes
Epidemic Disease
sudden increase in occurrence of disease above expencted levels
Example of an endemic disease
the common cold
Example of an epidemic disease
cholera
Pandemic disease
increase in a disease through large populations and across continents
Example of a pandemic disease
plague, AIDS, covid-19
Significance of understanding the chain of infection
helps us develop strategies to prevent further infection and to control disease
What is the chain of infection?
1) the pathogen
2) source of pathogen
3) transmission to host
4) susceptibility of the host
5) exit from host
Etiological agent
the organisms that causes disease
What do you use to identify the etiological agent?
Kock’s postualtes
Examples of biological agents of disease
metazoans, protozoans, fungi, bacteria, viruses, prions
Reserviours
the site or natural environment where the pathogen is normally found living and from which infection can occur
What are the two types of human reservoirs?
acute clinical cases and carriers
Incubatory carriers
just get sick and recover
Convalescent carriers
recover but still shed disease
Chronic carriers
sick and shed disease
Asymptomatic
no symptoms and shed disease
True or False: there are many kinds of animal reservoirs
True!
Zoonotic infection
infectious disease originating from animals, can be transmitted from one type of animal to another and may be transmitted to humans
Examples of zoonotic infection
plague, rabies, west nile, monkeypox
Examples of environmental reservoirs
plants, soil, watr
Can you easily get rid of pathogens in environmental reserviours?
No!
Direct transmission
an infectious agent is transferred from a reservoir to a susceptible host by direct contact or droplet spread
Indirect transmission
the transfer of an infectious agent from reservoir to a host by suspended air particles, inanimate objects, or animate intermediaries
What are animate intermediaries called?
vectors
What are inanimate objects called?
vehicles
What four things impact host susceptibility?
1) genetic factors
2) general resistance factors
3) specific acquired immunity
4) host variability (timing)
What are five things that impact host variability?
1) nutrition
2) stress levels
3) physical damage to tissue
4) behavioral differences
5) environmental conditions
What are some ways in which a pathogen can exit from a host?
coughing, insect bite, removal of blood, skin cells, urine, feces
What are the Cholera Stages of Disease?
1) incubation period
2) prodromal period
3) period of illness
4) period of decline
5) period of convalescence
Incubation period
no signs or symptoms; few hours to few days
Prodromal period
mild signs/symptoms; 1-2 days if any
Period of illness
disease most severe; symptoms of diarrhea, nausea, vomiting
Period of decline
signs and symptoms subside; decreased diarrhea; begin response to rehydration therapy and antibiotic treatment
Period of convalescence
person regains strengths and the body returns to normal; some people can become reservoirs of disease for months or even years
Who is most at risk of contracting cholera?
those who do not have access to piped safe water and adequate and proper sanitation
Period of communicabiltiy
the time in which an infectious disease might be transferred
What is the period of communicability for cholera?
the duration of the stool-positive stage; can persist for several months
Infective dose
the number of pathogens required to infect a host
Index/primary case
the person who first gets the disease in a population
Common sources for infection of cholera?
contaminated water, contaminated foods, vegetables fertilized with human excreta, soiled hands, fish/shellfish eaten raw
Herd immunity
immunity in some individuals from vaccinations or naturally acquired can protect non-immune individuals from infection
Host variability factors for cholera
1) poor sanitary conditions
2) raw or undercooked shellfish
3) reduced or nonexistent stomach acid
4) household exposure
5) type O blood
What are three epidemic control measures for cholera in Haiti?
1) proper sanitation
2) sterilization of waste
3) quarantine
4) destruction of domestic animal reservoirs
5) immunization
6) public health education
7) increased accessibility to treatment
