Epidemiology Flashcards
What is a disease?
a pathological condition of body parts or tissues characterized by an identifiable group of signs or symptoms
Infectious Disease
A disease caused by an infectious agent such as a bacterium, virus, protozoan, or fungus that can be passed on to others.
What is an infection?
occurs when an infectious agent enters the body and begins to reproduce; may or may not lead to disease
Host
an organism infected by another organism
Pathogen
an infectious agent that causes disease
What are some types of pathogens?
-virus
-bacterium
-fungi
-metazoa
-prions
-protazoa
What are emerging diseases?
-diseases that have recently appeared within a population or whose incidence or geographic range is increasing rapidly.
What causes a disease to emerge or re-emerge?
¤ appearance of a previously unknown agent.
¤ evolution of a new infectious agent.
¤ spread of an infectious agent to a new host.
¤ spread of an infectious agent to new locations.
¤ acquisition of resistance to anti-microbial drugs.
¤ deliberate introduction into a population.
Endemic/enzootic
-constantly present in a certain population or region with relatively low spread
Epidemic/epizootic
when there is a sudden increase in cases spreading through a large population like a country
Pandemic/Panzootic
when there is sudden increase in cases spreading through several countries
What makes up the epidiomelogical triangle?
Host, environment, vector
Outcomes of exposure
-No infection
-Subclinical Infection–> immunity, carrier state ,no immunity
-Clinical–> no immunity= death
Incubation period
time between infection and the appearance of signs and symptoms.
Signs
are the physical manifestation of disease or injury that are measurable and reproducible and that can be recognized by any observer,
usually a health practitioner.
Symptoms
are clinical manifestations of a disorder of organs or systems
that can be recognized or perceived only by patients.
Prodromal phase
mild, nonspecific symptoms that signal onset of some diseases.
clinical Phase
a person experiences typical signs and symptoms of disease
Decline phase
Subsidence of symptoms
Recovery Phase
symptoms have disappeared, tissues heal, and the body regains strength
Mechanism of Disease
microbes cause disease in the course of stealing space, nutrients, and or living tissue from their symbiotic hosts
How do microbes cause disease?
– Gain access to the host (contamination)
– Adhere to the host (adherence)
– Replicate on the host (colonization)
– Invade tissues (invasion)
– Produce toxins or other agents that cause host harm (damage)
What is infectivity?
The ability to infect the host
What is pathogenicity?
the ability to cause disease in the host
Virulence
the ability to cause severe disease in the host
Immunogenicity
the ability to induce an immune response in the host
Modes of transmission; Indirect contact
¤ Via vector (an organism that carries disease-causing micro-
organisms, such as mosquito)
¤ Via dust particles, air, food, water, blood, tissues, organs,
fomites (inanimate objects that can carry disease-causing
micro-organisms—e.g., toothbrush, cutting board, toys, etc.
¤ Diseases that are commonly spread by means of fomites include the
common cold, cold sores, conjunctivitis, coxsackievirus (hand-foot-
mouth disease), croup, E. coli infection, Giardia infection, influenza,
lice, meningitis, rotavirus diarrhea, RSV, and strep
Modes of transmission; direct contact
¤ Direct contact (person-to-person)
¤ Skin, saliva via kissing, sexual contact, aerosol from sneezing
or coughing (e.g. .Polio, hepatitis, HIV, influenza)
Modes of transmission; vertical transmission
-transmission of disease from mother to child
-just before or just after birth
-through placenta or breast milk
Modes of transmission; horizontal transmission
all other transmission person to person
What is epidemiology?
the study of the distribution and determinants of health-related states or events in specified populations, and the application of this study to the control of health problems (CDC).
Ratio
is the relative magnitude of two quantities or a comparison of any two values.
The numerator and denominator need not be related. Therefore, one could compare
any two events
Proportion
is the comparison of a part to the whole. It is a type of ratio in which the
numerator is included in the denominator. A proportion may be expressed as a
decimal, a fraction, or a percentage.
Rate
-is a measure of the frequency with which an event occurs in a defined
population over a specified period of time.
Ex. Number of COVID test in CA last week: 516,536
Number of positive tests last week: 21,843
Calculate the positivity rate for last week:
What is prevalence?
The number of persons with a specific disease at a specific time point
Incidence
number of proportion of persons developing a specific disease during a time period
Morbidity
refers to the number of persons that are ill
Mortality
Number or proportion of persons dying during a time period
Fatality rate
-Proportion of persons dying from a specific disease among all persons
with the disease.
Attack rate
-proportion of cases developing the disease among all persons who were
exposed to the disease
Herd Immunity
Herd immunity is the resistance of a group to attack from a disease to
which a large portion of members are immune, thus lessening the
likelihood of a patient with a disease coming into contact with a susceptible individual.
