Biology + Human Disease Risk Flashcards
strength of association (Hills Criteria)
strong associations are more likely to be causal than weak associations
consistency
repeated observations of an association in different populations under different circumstances
specificity
requires that a cause leads to a single effect, not multiple effects.
temporality
the necessity that the cause precedes the effect in nature
biologic gradient
refers to the presence of a uni-directional dose-response curve
Ex: more smoking = more carcinogenic exposure
plausability
refers to the biologic plausibility of the hypothesis;
often flawed
coherence
implies that a cause and effect interpretation for an association does not conflict with what is known of the natural history and biology of the disease
The Epidemiologic Triangle
models the relationship between:
agent - host - environment
Chain of Infection
Agent - Reservoir - Portal of Exit - Mode of Transmission - Portal of Entry - Susceptible Host
Agent
causes disease
ex: bacteria, viruses, parasites
Reservoir
habitat where agent normally lives, grows, and multiples
ex: humans, animals, environment (soil, water)
Zoonosis
an infectious disease that is transmissible under natural conditions from vertebrate animals to humans
Portal of exit
path by which an agent leaves the host
ex: mouth, cuts, urine or stool
Mode of Transmission
transfer of agent from reservoir to a host
Direct -or- Indirect
Direct transmission
direct contact (person or soil)
droplet spread (aerosols produced by sneezing, coughing, or talking)
Indirect transmission
airborne (dust or droplet suspension),
vehicles (food, water, blood, fomites)
vectors (mosquitos, fleas, ticks)
portal of entry
manner in which agent enters a susceptible host;
dermal, transplacental, oral, respiratory/inhalation
susceptible host
depends on genetics, immunity, or other determinants of health
Louis Pasteur
proved that germs caused disease (Germ Theory);
created first vaccines for rabies and anthrax
invented technique of treating milk to stop bacterial contamination (pasteurization)
Koch’s postulates
4 criteria to establish a causal relationship between agent and disease
anthrax; tuberculosis; later generalized to other diseases
Not all 4 postulates is required to demonstrate causality
Koch postulate 1
- agent must be found in all organisms with the disease, but not in healthy organisms
Koch postulate 2
- agent must be isolated from a diseased organism and grown in culture
Koch postulate 3
- cultured agent should cause disease in a healthy organism
Koch postulate 4
agent must be re-isolated and matched with original agent
mechanical vector transmission
living organism carries an agent from one host to another, but not as an infection
biological vector transmission
living organism carries an agent from one host to another as an infection
vehicle transmission
food, water, blood, fomites;
non-living item passively carries agent
fomite
inanimate objects that become contaminated with the agent
classical example: park water fountain
malaria biological vector
anopheles mosquito
break-bone/dengue fever biological vector
Aedes aegypti mosquito
yellow fever biological vector
Aedes aegypti mosquito
west nile fever biological vector
culex mosquito
west nile fever reservoir
birds
zika biological vector
Aedes aegypti mosquito
trachoma mechanical vector
housefly
plague biological vector
flea
lyme disease biological vector
tick
rocky mountain spotted fever biological vector
tick
sleeping sickness biological vector
tsetse fly
leishmaniasis biological vector
sandflies
river blindness biological vector
black flies
guinea worm biological vector
water fleas
malaria causative agent
plasmodium (protozoan parasite)
break-bone/dengue fever causative agent
dengue virus
yellow fever causative agent
yellow fever virus
west nile fever causative agent
west nile virus
zika causative agent
zika virus
trachoma causative agent
chlamydia trachomatis
plague causative agent
Yersinia pestis
lyme disease causative agent
borrelia burgdoferi
rocky mountain spotted fever causative agent
rickettsia rickettsii
sleeping sickness causative agent
trypanosoma bruceii
Japanese encephalitis biological vector
culex mosquito
Japanese encephalitis causative agent
Japanese encephalitis virus
SEIR Model
Susceptible, Exposed, Infected, Recovered
models progress of epidemic; not the most accurate predictors, but helpful in identifying drivers of infection
surveillance
monitors disease trends; identifies epidemics or new syndromes; planning public health policy; evaluating public health policy/intervention
passive surveillance
providers or labs report cases to health departments;
most common b/c efficient, simple and inexpensive, is continuous
cons: incomplete data due to underreporting
active surveillance
health department contacts providers and labs requesting case info.
Pro: More complete data; capture more cases
cons: expensive and time consuming
Epidemic prevention strategies
pasteurization, disinfection, barrier methods, antibiotics, quarantine, vaccination
How vaccines work
trigger the body’s adaptive immune system (antibody production) to target a specific agent
acquired immunity
immunity that develops during your lifetime
active immunity
develops in response to a direct infection
natural: actual infection
artificial: vaccination
passive immunity
develops after receiving antibodies from someone or treatment
natural: from mother through breast milk
artificial: treatment (gamma globulin injection or infusion)
herd immunity
resistance within a population to a certain infection
different thresholds for different diseases
higher infectious disease require higher thresholds
antigenic drift
minor change within genes
ex: point mutations in seasonal flu viruses
occurs in both influenza A & B viruses
may cause epidemics
antigenic shift
major change within genes, creates a new subtype
ex: exchange of gene segments
occurs in ONLY influenza A
may cause pandemic
disease is caused by:
complex interactions between genes and environment
demographic transition
high birth and death rates to low birth and death rates
agricultural to industry
infectious to chronic diseases
congenital defects
defects present at birth
What is part of the recommended uniform newborn screening panel?
- metabolic disorders;
- endocrine disorders;
- hemoglobin disorders;
- hearing loss
most genetic conditions screened for in newborn panels follow _____.
an autosomal recessive pattern of inheritance
teratogens
agents that induce defects during prenatal development;
half are unknown
teratogens: 3 types
- ionizing radiation
- chemicals
- pathogens
teratogen: ionizing radiation (2)
gamma rays
x-rays
cause microcephaly or intellectual disabilities
teratogen: chemicals (5)
- Accutane: birth defects
- Alcohol: fetal alcohol syndrome
- Cigarette use: LBW, stillbirth, miscarriage
- Dioxin: linked to cancer
- Thalidomide: absence of long bones
teratogens: pathogens (3)
- rubella: congenital defects
- syphilis: microcephaly or intellectual disabilities
- toxoplasmosis: stillbirth, miscarriage, developmental disabilities
most teratogens affect the embryo during _____.
organogenesis
currently the most common cause of unintentional deaths for adults in the US?
unintentional poisoning; drug abuse
Clean Air Act
requires EPA to set National Ambient Air Quality Standards;
regulated vehicle emissions
National Ambient Air Quality Standards (NAAQS)
6 primary criteria air pollutants:
- sulfur dioxide
- nitrogen oxides
- carbon monoxide
- ozone
- lead
- particulate matter
sulfur dioxide (NAAQS)
acid rain;
linked to respiratory effects
affects asthma
nitrogen oxides (NAAQS)
smog, acid rain;
linked to respiratory effects;
affects asthma
carbon monoxide (NAAQS)
reduces oxygen in body tissue;
affects cardiovascular conditions
ozone (NAAQS)
causes airway irritation, coughing, difficulty breathing;
affects asthma and COPD
lead (NAAQS)
linked to neurological defects;
particulate matter (NAAQS)
smaller than 10 micrometers;
linked to respiratory effects;
affects asthma
natural ozone
O3; found in stratosphere;
absorbs most of sun’s UV radiation
ground-level ozone
principal component of smog;
causes aging lung tissue and breathing problems
How climate change affects public health
- warm winters and hot, wet summers lead to increase vector borne diseases
- increased rain and flooding lead to increased mosquitos
- higher CO2 levels lead to increased pollen which increases asthma rates
greatest driver of climate change
greenhouse gases
- created by humans
greenhouse gases (5)
- carbon dioxide
- methane
- nitrous oxide
- ozone
- water vapor
non-point source pollution
unclear, indirect source
point-source pollution
clear, direct source;
runoff
organophosphates
widely used in insecticides
chloroflurocarbon
volatile organic compounds
EPA regulates the following pathogens in water sources:
- cryptosporidium
- giardia lamblia
- legionella
- enteric viruses
Steps in Water Treatment
- Coagulation + Flocculation
- Sedimentation
- Filtration
- Disinfection
Coagulation + Flocculation
- chemicals with + charge are added to water;
- neutralizes - charge of dirt
- causes particles to bind with chemicals and form larger particles called floc
Sedimentation
floc settles to the bottom of the water due to weight
Filtration
clear water above settled floc passes through filters
Disinfection
chlorination kills remaining parasites, bacteria, viruses
Legionnaire’s Disease causative agent
legionella pneumophila (bacteria)
Legionnaire’s Disease source
contaminated water that contained the bacteria
legionella pneumophila (bacteria) causes 2 disease
- Legionnaire’s
2. Pontiac River Fever
cryptosporidium can become a problem in water supplies because _____.
it can survive the chlorine treatment process
Danger Zone
40F to 140F
Hemolytic Uremic Syndrome is caused by _____.
E. coli strain 0157:H7
Pregnant women are 10 time more likely to become infected with _____, which may cause _____.
Listeria;
may cause miscarriage, stillbirth, or preterm labor
Common pathogens associated with chicken (3)
- salmonella,
- campylobacter,
- Listeria
Common pathogens associated with fish (2)
- scombroid toxin
2. ciguatoxin
Common pathogens associated with produce (2)
- salmonella
2. Listeria
HACCP
Hazard Analysis Critical Control Point
system for reducing the risk of safety hazards in food
HACCP Steps:
- Conduct hazard analysis
- identify the critical control point
- establish critical limits
- establish monitoring procedure
- establish corrective action
- establish record keeping procedures
- establish verification procedures
The Love Canal
Entire town was relocated when hazardous waste was discovered to be disposed below the town.
high rates of miscarriage, birth defects, and cancer
near Niagara Falls in 1952
Superfund
created and administered by the EPA;
responsible parties must assume liability for the clean up of environmental hazards they cause
Superfund site
any land contaminated by hazardous waste and identified by the EPA as a candidate for cleanup due to risk to human health
In the U.S., which is the largest source of radiation dose to the general public?
radon gas
toxicology
study of how chemicals cause injury to living cells
dose
amount of chemical in the body
risk
probability that harm will occur
= toxicity x exposure
acute toxicity
one time exposure causes systemic damage
ex: hydrogen sulfide exposure
chronic toxicity
long-term, low-level exposure to chemicals causes harmful systemic effects
ex: asbestos exposure
dose-response curve
assumes higher dose = greater
effects
exception: carcinogens (no safe threshold)
LD50
dose level at which 50% of the test population will die
LD0
dose level with no deaths
Toxic Substances Control Act (TSCA)
mandated safety and health data on chemicals;
required EPA to regulate substances that pose a risk to human or environment health
Clean Water Act
formerly the Water Pollution Control Act;
Established national standards for waterways and set limits on pollutant discharges.
Comprehensive and Environmental Response Compensational and Liability Act (CERCLA)
created superfunds to provide clean up of existing inactive and abandoned hazardous waste sites
Federal Water Pollution Control Act in 1972
was later renamed to Clean Water Act of 1977;
Established national standards for waterways and set limits on pollutant discharges.
Safe Drinking Water Acts
regulated public drinking water systems;
allowed EPA to set maximum contaminant levels for water pollutants in drinking water
Comprehensive Air Quality Act of 1967
1st attempt to develop regional approach for air pollution control through Air Quality Control Regions;
oversight of air quality was at state level
Clean Air Act (1970)
moved oversight of air quality from state to federal level EPA
Resource Conservation and Recovery Act
prevents hazardous waste problems at active sites;
mandated cradle-to-grace tracking system
Community Right-to-Know Act
private and public facilities are required to report publicly their waste production for hazardous wastes
Hazardous materials transportation act
provided guidance on the transportation of hazardous materials;
overseen by Department of Transportation;
states can set more stringent provisions
