Chapter 19 Epidemiology Flashcards
Rates of disease in a population
- Attack rate: percentage of people who become ill in population after exposure to infectious agent (more significant)
- Incidence: number of new cases/time/population
- Prevalence: total number of cases at any time or for a specific period in a given population
- Morbidity: incidence of disease in a population
- Mortality: overall death rate in population
- Case-fatality rate: percentage of population that dies from a
specific disease
rates of disease in a population …
- Endemic disease: constantly present in population
- Sporadic: a few cases from time to time
- Epidemic: unusually large number of cases (can be from introduced or endemic disease)
- Outbreak: group of cases at specific time and population
- Pandemic: is global
Chain of Infection
- Reservoir of infection: natural habitat of pathogen
- In or on animal, human, or in environment (soil, water)
- Identification is important in disease control - Portal of exit: body surface or orifice: exit route for pathogen
- Intestinal tract: shed in feces
- Respiratory tract: exit in droplet of saliva/mucus - Disease transmission
- Vertical transmission: pregnant woman to fetus or
mother to infant during childbirth, breast feeding
- Horizontal transmission: person to person via air,
physical contact, ingestion of food or water, or vector
*direct contact: touch
- Indirect transmission: object, food, water
4.Portal of entry: body surface or orifice: entry route for
pathogen
- Respiratory pathogens -inhaled (nose)
- Intestinal pathogens -ingested (mouth)
- Susceptible Host: the organism that will feel the effects of the infectious disease
How can characteristics of a pathogen influence the epidemiology of a disease?
Pathogen: easier to control if humans are only reservoir
- Virulence- ability to cause disease
- The dose- number of pathogens introduced; minimum number of pathogens required to produce symptoms
- Incubation period - influences extent of spread
(long incubation period can allow extensive spread before first symptoms appear)
How can characteristics of a host influence the epidemiology of a disease?
Host:
- Immunity to pathogen: previous exposure, immunization
* Herd immunity: protects non-immune individuals in
population; >90% immunity typically sufficient
* Antigenic variation: can overcome herd immunity
- General health: malnutrition, overcrowding, fatigue
* Age: very young, elderly generally more susceptible
How can characteristics of the environment influence the epidemiology of a disease?
Environment:
- Temperature, water and nutrient supply, radiation, and
the availability of light and
- Crowding and poor sanitation
- Endospores: bacteria extremely resistant to heat
- Exposure to antibiotics
Compare and contrast (descriptive studies), analytical studies, and experimental studies?
Descriptive Studies: data collected (time, place, the
individuals affected) during an outbreak to determine
possible risk factors for disease spread
* The person
* The place:
* The time
Compare and contrast descriptive studies, (analytical studies), and experimental studies?
Analytical Studies: determine which risk factors are
relevant to disease spread
* Case-control study: attempts to identify chain of events
leading to disease; selection of controls is important
* Cross-sectional study: surveys population at one point
in time
* Cohort studies: groups with known exposure to risk
factor are selected and followed over time
Compare and contrast descriptive studies, analytical studies, and (experimental studies)?
Experimental Studies: cause/effect relationship of risk factors and development of disease
* experimental treatment compared with known treatment aka “placebo”
Describe how a common-source epidemic can be distinguished from a propagated epidemic
A common source epidemic is when the affected individuals have a common agent whereas the propagated epidemic is a slow rise in cases
Describe the roles of the Centers for Disease Control and Prevention
provides support for labs in the U.S. and abroad
* collects data on diseases that impact public health
* Publishes Morbidity and Mortality Weekly Report (MMWR)
* Collects data on over 50 notifiable diseases (with state health departments)
* Conducts research on infectious disease
Describe the activities of the World Health Organization
- Provide worldwide guidance in field of health
- Set global standards for health
- Cooperatively strengthen national health programs
- Develop and transfer appropriate health technology
Describe the conditions that may allow eradication of a disease
improved sanitation
reservoir and vector control
vaccination
antibiotic treatment
Explain how microbial evolution can lead to emergence of disease
The emergence of some diseases follows the natural evolution of mircobes
- ex: the virus that causes COVID19 appears to have evolved from a virus that infects bats
Describe how human behavior can contribute to the emergence and reemergence of disease
- Population expansion
- Climate changes
- Advances in technology
- Importation of food
