Public Health Biology and Human Disease Risk Flashcards
Models of Disease Transmission
Transmission modeling is often to understand the factors that are responsible for the persistence of transmission, the dynamics of the infection process and how best to control transmission.
What are the main components of the epidemiologic triad?
Agent/pathogen, Host, and Environment
Causative Agent
Any microorganism that can cause infection
Reservoir or Source
The environment where the agent resides; water sources, feces, bodily secretions, etc.
Portal of Exit
How the agent leaves the reservoir or the host
Mode of Transmission
How the agent travels to another host; transmission can be direct or may include an intermediate or indirect contact
Portal of Entry
Where the infectious agent enters a susceptible host.
Susceptible Host
Individual or animal that is susceptible to infection.
What are important characteristics to consider about a host?
- age
- prior exposure
- susceptibility
- co-infection
- immune response
What are important characteristics to consider about an agent/pathogen?
- toxicity
- virulence
- infectivity
- susceptibility to antibiotics
- ability to survive outside the body
What are important characteristics to consider about an environment?
- climate
- physical structures
- population density
- social structure
What are examples of public health interventions that have diminished infectious disease burden?
- clean water
- sanitation
- vaccination
Disability Adjusted Life Years (DALYs)
Metric used to take the morbidity as well as mortality into account when one is calculating the overall burden of disease.
*Often used to determine cost-effectiveness of various disease interventions
Vectorial Capacity
A key metric that determines if a given insect can serve as an efficient biological vector.
Basic Reproductive Number (R)
Key parameter that determines if a pathogen will cause an epidemic or not.
R0
This is the basic reproductive number at time zero and is an estimate of the average number of new cases that the initial infection is capable of spawning.
What does it mean when R = 1?
When R=1, every case of infection will result in an average of one new case and the infection will be in equilibrium.
What does it mean when R > 1?
When R>1, the incidence of the infection will increase and an epidemic will result.
What does it mean when R < 1?
When R<1, the infection will disappear from the population.
What is the SEIR model?
SEIR = susceptible, exposed, infectious, and recovered.
A type of epidemiologic model.
Adaptive Immunity
This type of immunity can be active or passive and can be naturally or artificially acquired.
According to the WHO chronic diseases accounted for ____ of all deaths worldwide in 2012.
The majority of these deaths (____) are attributable to CVD, cancers, chronic respiratory diseases, and diabetes.
68%
82%
Gene defects
point mutations
Cytogenetic defects
results of chromosomal abnormalities
Epidemiologic Transition
The shift toward an increasing global burden of noncommunicable disease.
What are the 3 stages of epidemiologic transition?
- The age of perstilence and famine
- The age of receding pandemics
- The age of degenerative and man-made diseases
What is a challenge to addressing noncommunicable diseases?
There is a relative lack of understanding of the etiology of non-communicable diseases.
Ecobiologic Factors
Ex: air pollution
Factors specific to the host as well as the environment.
How much does violence and injuries cost the US in medical care and lost productivity annually?
$600 billion
What is our air composed of?
78.1% nitrogen, 20.9% oxygen, and 0.9% argon.
Remaining 0.1% is made of carbon dioxide, neon, helium, and methane.
What are the 6 primary air pollutants?
- sulfur dioxide (acid rain)
- Nitrogen oxides (smog, acid rain)
- Carbon monoxide
- Ozone
- Lead
- Particulate matter (PM2.5 and PM10)
Ground-level ozone is…
A principle component of smog
Atmospheric ozone is…
Has a positive effect on human health.
How much has the earth’s average temperature increased in the past 100 years?
1.5F
What are the current indications of climate change?
- changes in weather patterns
- rising global temperatures
- increases in surface temperatures of the oceans
- melting of glaciers and polar icecaps
Greenhouse Gasses
The largest driver of climate change.
*Includes: water vapor, carbon dioxide, nitrous oxide, ozone, chlorofluorocarbons, and hydrofluorocarbons.
Point Source pollution
Pollution that comes from a direct source like a factory or hazardous waste site.
Nonpoint Source pollution
Pollution from a diffuse source like runoffs coming from agricultural sources, construction, streets or mines.
Which organization regulates drinking water?
EPA
Which pathogens does the EPA regulate in drinking water?
- Cryptosporidium (protozoan, contaminated surface waters by sewage and waste, resistant to chlorine)
- Giardia lamblia (protozoan, contaminated soil/food/water by feces)
- Legionella (bacteria, hazardous if aerosolized and inhaled)
- Enteric viruses (includes rotovirus and norovirus)
What are the steps for water treatment?
- Coagulation and flocculation
- Sedimentation
- Filtration
- Disinfection
What occurs during coagulation and flocculation?
Chemicals with a positive charge are added to the water to neutralize the effects of dirt and other dissolved particles.
Particles + Chemicals = Larger Particles = Floc
What occurs during sedimentation?
Floc settles to the bottom of the water.
What occurs during filtration?
After floc settles to the bottom, clear water on top passes through various filters to remove dissolved particles.
What occurs during disinfection?
After filtration, a disinfectant like chlorine is added to the water to kill remaining parasites, bacteria or viruses.
What steps are involved in the primary treatment phase of sewage treatment?
Primary phase: mechanical process removing 50%-60% of suspended solids
- Screening (removing large solids)
- Grinding (reduces solids to uniform size)
- Sedimentation (solids separated in a grit chamber)
- Primary clarification (floating scum and settles sludge are dried and disposed)
What steps are involved in the secondary treatment phase of sewage treatment?
Secondary phase: biological process removing 90%-95% of the suspended solids
- Activated sludge process (remaining sewage is oxidized to rapidly break down organic material)
- Secondary clarification (afloat scum and settled sludge are dried and disposed)
How is the effectiveness of sewage treatment measured?
By diminishing the biological oxygen demand (BOD).
What does chlorination do?
Chlorination can be taken as an additional step of sewage treatment to control disease transmission.
What is the danger zone?
Temperatures between 39F and 140F.
How are foodborne illness outbreaks handled?
- typically controlled for at the local or state level
- health agencies are required to report all cases of food-borne illness to the CDC
- FDA will get involved with any FDA-regulated food/product
Hazard Analysis and Critical Control Points (HACCP)
HACCP is a preventative measure developed as a systematic approach to the identification, evaluation, and control of food safety hazards.
What are the 7 HACCP principles?
- conduct hazard analysis
- determine critical control points
- establish critical limits
- establish monitoring procedures to allow the opportunity to take corrective action
- establish the corrective action to be taken when monitoring indicates that a critical limit has been exceeded
- establish procedures to verify that the HACCP system is working
- establish effective record keeping that will document the HACCP system
What are municipalities responsible for today?
solid waste disposal, recycling, landfilling, composting and combustion.
What does hazardous waste primarily come from?
- hazardous materials in the home (pesticides, cleaning products, painting supplies, automotive products)
- medical waste (chemicals, infectious agents, radioactive material)
- industrial hazardous waste (chemicals, solvents, and heavy metals)
- radioactive waste
- mining waste
Superfund Regulations
These regulations require responsible parties must assume liability for the cleanup of environmental hazards that they cause.
What are the 3 major routes of exposure?
- Dermal entry
- Inhalation (most common)
- Orally
Toxicology
The study of how chemicals cause injury to living cells and whole organisms.
Risk = Toxicity x Exposure
Risk is the probability that harm will be produced under a specific set of conditions.
What is assumed about the dose-response curve?
- the curve illustrates the change in effect on an organism that is caused by differing levels of exposure.
- it is assumed that the higher the dose, the greater the effects observed.
- deleterious effects are expected to occur after reaching a threshold dose amount
What is the carcinogen rule?
There is no safe threshold level (related to dose-response assumptions)
Lethal dose
50 (LD50) is the most common measure of acute toxicity = the dose level at which 50% of the test population is expected to die
Acute toxicity
The ability of a substance to do systemic damage as a result of a one-time exposure of a short duration.
Chronic toxicity
Systemic effects that are produced by long-term and often low-level exposure.
Risk Assesment
The methodology that assists in evaluating the human effects and environmental consequences of exposure to chemicals.
Hazard Identification (risk assessment step 1)
Determining if a chemical under exposure conditions likely to occur in humans can cause an increase in the incidence or severity of an adverse health effect.
Dose-response Assessment (risk assessment step 2)
This is the process of characterizing the relationship between the dose of a chemical and the severity and incidence of adverse health effects in an exposed population.
*considers duration, frequency, and magnitude of exposure as well as confounding issues like age, sex, and lifestyle factors.
Exposure Assessment (risk assessment step 3)
The process of identifying potential exposure routes, specifying an exposure population, and measuring or estimating the magnitude, duration, and frequency of exposure.
Risk Characterization (risk assessment step 4)
Developing of qualitative, semi-quantitative, or quantitative estimate of risk associated with a given chemical under a defined exposure with varying sensitivities and exposures.
What source is the most common route of exposure for children with lead toxicity?
lead-based paint
What is the leading cause of death among children?
motor vehicle injuries
What are the EPA criteria air pollutants?
carbon monoxide, lead, ground-level ozone, nitrogen dioxide, particulate matter, and sulfur dioxide.
