Final exam - Week 4 Flashcards
what is a disease caused by the invasion and growth of pathogenic agents or microbes in a host?
infectious disease
What is infectious disease synonymous with?
communicable disease
true or false: infectious disease is always contagious
false; may or may not be
true or false; IDs are among the leading causes of death
true
What are illnesses capable of transmission directly or indirectly among humans?
contagious
What 3 factors comprise the epidemiological triangle of disease? what additional?
- host
- agent
- environment
- vector - center
What are agent factors associated with?
the pathogen causing the infection
What are host factors associated with?
those internal to the animal or human invaded by the agent that contribute to its susceptibility and infectiousness
What are environmental factors?
are everything else external to the host and agent that influence the transmission and development of an infectious disease
What is a vector?
are organisms, usually invertebrate arthropods like mosquitoes and ticks, that transmits a agent from one host to another
Host factors that contribute to infectious disease transmission include what?
those that effect host susceptibility as well as those that relate to the host infectiousness
What does susceptibility include?
both host resistance and immunity
What role has genome scanning had in ID?
they have been able to identify genes associated with specific infectious diseases.
What factors are under resistance for susceptibility?
- Genetics
- Age/ gender/ancestry
- Pregnancy
- General health
- Nutrition
- Chronic diseases
- Stress
what is an innate resistance to a specific antigen or toxin, such as through genetics which we just discussed?
natural immunity
What does acquired immunity come from?
from actual exposure to a specific infectious agent and is further divided into two subcategories, active and passive.
When does active immunity occur?
occurs when the host stimulates its own antibodies thru exposure to the agent, either through natural exposure or exposure with an immunization
When does passive immunity occur?
when antibodies are transferred to the host, either through mother to infant or through immune globulin or antitoxin.
what is the resistance of a population to the infection because a high proportion of individual members are resistant?
herd immunity
What 2 things can herd immunity be?
- natural due to genetics
2. acquired from past exposure
What do immunizations provide?
active immunity for the individual and herd immunity for the community.
What is the ability of an infected host to transmit infection?
infectiousness
What is the infected host usually referred to as?
as the human or animal reservoir for the infectious agent
What are the 3 stages of infection?
- latent
- communicable
- incubation
What is the latent stage of infection?
begins with exposure and ends when the pathogen begins to shed.
Are people infectious during the latent stage of infection?
no
What is the communicable stage characterized by?
the shedding of the pathogen
what is the progression of the communicable stage?
begins before symptoms and ends after symptoms disappear
Is a host infectious during the communicable stage?
yes
Only what type of disease has a period of communicability?
contagious disease
When does the incubation stage begin and end?
begins with exposure to the agent like the late stage and ends when symptoms appear
When is a host frequently infectious?
when they are asymptomatic
For diseases like tetanus and Lyme disease, which are not infectious, what is unique about them?
they have an incubation and disease period, but latent and communicability periods do not apply
What are organisms capable of producing infection in a host?
infectious agents
What are the 4 infectious agents?
- bacteria
- viruses
- parasites
- fungi
What are the 3 ways an agent interacts with its host?
- infectivity
- pathogenicity
- virulence
What is infectivity?
refers to the ability of an agent to enter, survive and multiply in a host or their power to invade and infect large numbers of people.
What is infectivity a characteristic of? infectiousnessness?
a. agent
b. host
What is the agents ability to cause disease and refers to the proportion of infected people who actually develop the disease?
pathogenicity
Infectious agents that cause a large percentage of subclinical infections are said to have what?
low pathogenicity
What is the ability to produce a severe pathological reaction and refers to the proportion of infected people who died or become severely disability?
virulence
How is the virulence of a disease often measured?
in terms of mortality rate
What are the environmental factors in the epidemic triangle?
all those that are external to the animal or human host and the agent
What can environmental factors be?
- physical
- biological
- social
- cultural
What are examples of environmental factors that can impact infectious disease?
- Location (institutions, geography, spectrum of disease)
- Non-living reservoirs (soil, water)
- Climate change and extremes
- Insects and animals
- Body fluids
- Crowding, education, resources and access to care
- Norms, health beliefs, health behaviors
What is an endemic?
occurring at a consistent, expected level in a defined and often limited area geographic area
What is an outbreak?
unexpected occurrence or increase; limited geographical area; limited period of time.
What is an epidemic?
unexpected occurrence or increase; in a defined but larger geographical area; extended period of time
What is a pandemic?
epidemic that has spread over several countries or continents, usually affecting a large number of people.
What is the means by which an agent is transmitted from one host or inanimate reservoir to a host?
modes of transmission
What are modes of transmission impacted by?
- host
- agent
- environmental factors
What is vertical transmission?
the passing of the infection from parent to offspring via sperm, placenta, milk, or contact in the vaginal canal at birth
What is horizontal transmission?
the spreading of infection from a host or reservoir to a person and includes direct, indirect, airborne and vector transmission
true or false; horizontal transmission is limited to contagious diseases.
false; it is not
How do direct transmissions occur?
by immediate transfer of pathogen from an infectious host to a susceptible host.
What does direct transmission include?
includes touching, sexual intercourse, kissing,, biting.
When does indirect transmission occur?
occurs when the infectious agent is transported via contaminated inanimate reservoirs such as air, water, door knobs, counters, eating and drinking utensil, personal care products and medical supplies such as shares.
How does direct transmission occur?
occurs by immediate transfer of pathogen from an infectious host to a susceptible host and includes touching, sexual intercourse, kissing,, biting.
Can droplet be vertical and horizontal?
yes, but is usually horizontal
When does indirect transmission occur?
occurs when the infectious agent is transported via contaminated inanimate reservoirs such as air, water, food, door knobs, counters, eating and drinking utensil , personal care products and medical supplies such as sharps
What is a type of indirect transmission which occurs through droplet nuclei or dust particles?
airborne transmission
How is airborne different from droplets?
much smaller and can travel farther and also remain suspended for long periods before they are inhaled by a host