Public Health Biology and Human
Disease Risk CPH
Epidemiological Triangle - ANSagent, host, environment
disease occurs when an outside agent (entity that causes disease, can be chemical, physical, or
biological) capable of causing the disease interacts with a vulnerable host (susceptible
organism, human, animal) in an environment (conditions that are not part of the agent and/or
host but influence their interaction)
chain of transmission - ANSillustrates how infectious agents develop and spread
1. causative agent- any microorganism that causes infection
2. reservoir source- the environment where the agent resides; water, feces, bodily secretions
3. portal of exit- how the agent leaves the reservoir of the host
4. mode of transmission- how the agent travels to another host; may be direct or may include an
intermediate or indirect contact
5. portal of entry- where the infectious agent enters susceptible host
6. susceptible host- individual or animal that os susceptible to infection
5.
DALY - ANSdisability adjusted life years
measure of the burden of disease that takes into account morbidity AND mortality
one DALY equals to one year of healthy life lost due to premature death or time lived with
illness, disease or injury
DALYs for a disease or health condition are the sum of the years of life lost to due to premature
mortality (YLLs) and the years lived with a disability (YLDs) due to prevalent cases of the
disease or health condition in a population.
used as a way to measure the cost-effectiveness of interventions
QALY
The basic idea underlying the QALY is simple: it assumes that a year of life lived in perfect
health is worth 1 QALY (1 Year of Life × 1 Utility = 1 QALY) and that a year of life lived in a state
of less than this perfect health is worth less than 1.
, Modes of Infectious Disease Transmission - ANS1. direct contact- transmission requires direct
contact with tissues, blood, bodily fluids, or secretions from an infected individual or animal
2. indirect contact- similar to direct contact, but direct contact with bodily secretions or fluids is
not required; the pathogen may be capable of surviving on objects or surfaces for some period
of time and can be transmitted when an infected person comes into contact with the
contaminated surface or object (inanimate objects capable of transmitting a pathogen are
known as fomites)
3. airborne- transmission through the air, usually accomplished through droplets expelled from
an infected person from a cough or sneeze; effectiveness is a fxn of droplet size and
susceptibility of the pathogen to desiccation
4. water- and soil-borne- pathogens transmitted in this manner can survive for relatively long
periods of time in either soil or water and are transmitted when an individual ingests
contaminated soil, food, of water
5. vector-borne- represents that most significant class of infectious agents worldwide (can be
viruses, bacteria, unicellular eukaryotes, or multicellular invertebrates); insects are the most
common vectors of infectious disease
kinds of vectors - ANSmechanical- pathogens are carried from host to host by the vector without
infecting the vector
biological- more common and dangerous, the pathogen is able to infect, develop, and amplify
within the vector, resulting in a far more efficient transmission; however, this requires that the
pathogen can infect both invertebrate and human hosts, which are very different environments
vectorial capacity - ANSmetric that determines if a given insect can serve as an efficient
biological vector
V= overall vectorial capacity
m= density of the vector (number of vectors per acre)
a= probability the vector will feed on the vertebrate host of interested for the pathogen (humans)
p= daily survival probability (chance that an individual insect will live to see another day)
n= extrinsic incubation period (days it takes for an infected vector to become infectious)
b= competence of the vector (proportion of vectors that take up the pathogen that actually
become infectious)
agents and vectors for common biological vector-borne diseases - ANSmosquitos- malaria,
lymphatic filariasis (elephantiasis), breakbone fever, yellow fever, west nile fever, zika
housefly- trachoma
Disease Risk CPH
Epidemiological Triangle - ANSagent, host, environment
disease occurs when an outside agent (entity that causes disease, can be chemical, physical, or
biological) capable of causing the disease interacts with a vulnerable host (susceptible
organism, human, animal) in an environment (conditions that are not part of the agent and/or
host but influence their interaction)
chain of transmission - ANSillustrates how infectious agents develop and spread
1. causative agent- any microorganism that causes infection
2. reservoir source- the environment where the agent resides; water, feces, bodily secretions
3. portal of exit- how the agent leaves the reservoir of the host
4. mode of transmission- how the agent travels to another host; may be direct or may include an
intermediate or indirect contact
5. portal of entry- where the infectious agent enters susceptible host
6. susceptible host- individual or animal that os susceptible to infection
5.
DALY - ANSdisability adjusted life years
measure of the burden of disease that takes into account morbidity AND mortality
one DALY equals to one year of healthy life lost due to premature death or time lived with
illness, disease or injury
DALYs for a disease or health condition are the sum of the years of life lost to due to premature
mortality (YLLs) and the years lived with a disability (YLDs) due to prevalent cases of the
disease or health condition in a population.
used as a way to measure the cost-effectiveness of interventions
QALY
The basic idea underlying the QALY is simple: it assumes that a year of life lived in perfect
health is worth 1 QALY (1 Year of Life × 1 Utility = 1 QALY) and that a year of life lived in a state
of less than this perfect health is worth less than 1.
, Modes of Infectious Disease Transmission - ANS1. direct contact- transmission requires direct
contact with tissues, blood, bodily fluids, or secretions from an infected individual or animal
2. indirect contact- similar to direct contact, but direct contact with bodily secretions or fluids is
not required; the pathogen may be capable of surviving on objects or surfaces for some period
of time and can be transmitted when an infected person comes into contact with the
contaminated surface or object (inanimate objects capable of transmitting a pathogen are
known as fomites)
3. airborne- transmission through the air, usually accomplished through droplets expelled from
an infected person from a cough or sneeze; effectiveness is a fxn of droplet size and
susceptibility of the pathogen to desiccation
4. water- and soil-borne- pathogens transmitted in this manner can survive for relatively long
periods of time in either soil or water and are transmitted when an individual ingests
contaminated soil, food, of water
5. vector-borne- represents that most significant class of infectious agents worldwide (can be
viruses, bacteria, unicellular eukaryotes, or multicellular invertebrates); insects are the most
common vectors of infectious disease
kinds of vectors - ANSmechanical- pathogens are carried from host to host by the vector without
infecting the vector
biological- more common and dangerous, the pathogen is able to infect, develop, and amplify
within the vector, resulting in a far more efficient transmission; however, this requires that the
pathogen can infect both invertebrate and human hosts, which are very different environments
vectorial capacity - ANSmetric that determines if a given insect can serve as an efficient
biological vector
V= overall vectorial capacity
m= density of the vector (number of vectors per acre)
a= probability the vector will feed on the vertebrate host of interested for the pathogen (humans)
p= daily survival probability (chance that an individual insect will live to see another day)
n= extrinsic incubation period (days it takes for an infected vector to become infectious)
b= competence of the vector (proportion of vectors that take up the pathogen that actually
become infectious)
agents and vectors for common biological vector-borne diseases - ANSmosquitos- malaria,
lymphatic filariasis (elephantiasis), breakbone fever, yellow fever, west nile fever, zika
housefly- trachoma
