Lecture 14 - Diagnostic Microbiology and Epidemiology Flashcards
What is epidemiology?
Study of the Occurrence, Distribution and Determinants of Health and Disease
- Focuses on Public Health
- Health of the Human Population as a Whole
How do we classify disease?
Endemic
-restricted areas and low incidence
Epidemic
-restricted areas and high incidence
Pandemic
-worldwide and high incidence
What is incidence vs prevalence?
Incidence
- number of new cases
- record of disease spread
Prevalence
- Number of new and existing cases
- record of total disease burden
Faucet and bathtub example
What is mortality and morbidity?
Mortality
- incidence of death
- fatal cases only
Morbidity
- Incidence of disease
- fatal and nonfatal cases
What do we look at when we are trying to control and eradicate disease?
How do they live
Where do they live
How are they transmitted
How do pathogens live?
Host-Dependent
- grow/reproduce only in host
- cause chronic infections
Host-Independent
- grow/reproduce outside of the host
- acute infections
What are the stages of disease progression in acute infections?
Infection - pathogen invades, colonizes Incubation Period - pathogen grows, no symptoms Acute Period - appearance of symptoms Decline Period - decline of symptoms Convalescent Period - host recovery
Where do pathogens live?
Disease reservoirs
-Where they can reproduce, grow, and spread
Types
- Animate = living like lymes disease and ticks
- Inanimate = nonliving like soil
How is disease transmitted?
Direct Host-to-Host
- person to person = human to human
- zoonosis = non-human to human, human dead-end host
Indirect Host-to-Host
- Vectors = reservoir to human using living carrier
- vehicles = reservoir to human using nonliving carrier
What are the different types of epidemics?
Common-Source Epidemics
- Inanimate Reservoirs like contaminated water
- quick increase/decrease in number of cases
Host-to-Host Epidemics
- Animate Reservoirs like influenza
- longer duration but lower number of cases
What are the types of host-pathogen coevolution?
Selection pressures for mutual coexistence
- common for host-dependent pathogens
- decreased pathogen virulence and increased host resistance
No selection pressures for mutual coexistence
- common for host-independent pathogens
- pathogen virulence remains high but host resistance remains low
What are nosocomial infections?
Infections acquired by patients in hospitals
Selects for highly virulent, antibiotic resistant pathogens - host independent
- Low host resistance
- Many pathogen reservoirs
- Breaching of skin barrier
- Drug usage = antibiotic resistance
What is the Basic Reproductive Number R0?
Number of secondary cases from an infected individual
- how many ppl you transmit disease to
- R0<1, disease will die out
- R0=1 disease is maintained
- R0>1, disease outbreak, possible epidemic
How do we calculate the basic reproductive number, R0?
R0 = rcd
r=transmissibility
c=avg rate of contact between ppl
d=duration of infectious stage
What is herd immunity?
Prevent epidemics by limiting pathogen transmission
- the immune individuals protect pl w/o immunity
- increase pathogen virulence = more immune ppl needed to prevent epidemic
What public health measures do we take to identify, track, contain and eradicate infectious disease?
Disease Management
- Control against vehicles
- Control against reservoirs
- Immunization
- Quarantine
- Surveillance
How do we control against vehicles?
Water Purification
Food purity/preparation
-pasteurization
Air Filtration
-HVAC and air masks
How do we control against reservoirs?
Domestic Animals
-vaccination programs at vet
Wild Animals
-bait traps and oral vaccines
Insect vectors
-insecticides
How do we use immunization in disease management?
Highly controlled Child Immunization
Booster shots for adult immunization
How do we use quarantine in disease management?
Restricted movement of disease carriers
-prevent spread of highly contagious disease
Human and Animal Quarantine
- humans w/ active infections
- animals that are disease vectors
How do we use surveillance in disease management?
Monitor disease incidence and prevalence
- apply disease tracking data
- implement control strategies
CDC in U.S.
WHO internationally
What are emerging diseases and what are the types?
Sudden increase in disease prevalence
Types
- New Diseases
- Reemerging diseases
What are the factors of disease emergence?
- Human demographics and behavior
- Economic Development and land use
- International travel
- Pathogen adaptation
- Loss of health standards
What is biological warfare?
Use of biological agents to kill/incapacitate
Characteristics
-easy to produce/deliver
Delivery
- aerosol
- drinking water
- food
