Glossary of Microbiology: Chapter 37
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- Define Prevalence
- Prevalence is the number of cases at a given time/population unit
- Define morbidity
- Morbidity is the number of new cases/time period/population unit
- Define mortality
- Mortality is the number of deaths/number with disease
- Define outbreak
- An outbreak is a small, localized increase in the occurence of a disease
- Define index case
- An index case is the first disease case in an epidemic within a give population
- Define endemic
- Endemic is the basal level of a disease (if the endemic is high it is refered to as hyperendemic)
- Define epidemic
- An epidemic is a significant increase in the frequency of a disease
- Define pandemic
- A pandemic is a global epidemic (crosses continents)
- Differentiate between signs and symptoms of an infectious diseas.
- Signs of an infectious disease are objective changes that can be observed/measured (fever, rash, weight loss), while symptoms are subjective changes experienced by the patient (pain, nausea).
- What are the five stages of a typical infectious disease?
- The five stages of a typical infectious disease are 1) Incubation, 2) Prodromal, 3) Acute, 4) Decline, and 5)Convalescent periods.
- During which stage is a disease usually contagious?
- A disease is most usually contagious during the prodromal and acute periods, although it is sometimes contagious in incubation and decline periods.
- What is a syndrome?
- A syndrome is a typical or diagnostic set of signs and symptoms.
- What are Koch's postulates?
- How do the kinetics of propagated spread differ from common source epidemics?
- A propagated spread has a slow rise and a slow decline, while a common source epidemic has a sharp rise and a sharp decline.
- What is threshold density and what happens when the level is reached in a propagated epidemic?
- Threshold density is the minimum number of individuals necessary to continue propagating the disease. When threshold density is reached in a propagated epidemic the incidence of new cases ceases because the pathogen can not propagate itself.
- What are sources and reservoirs?
- A source is a location from which the etiologic agent is transmitted to the host. A reservoir is a habitat where the organism can reproduce and be a source for subsequent infections.
- What are examples of animate and inanimate reservoirs?
- An examples of animate reservoirs are animals (carriers). Examples of inanimate reservoirs are soil, water, etc.
- What is a carrier?
- A carrier is an infected individual that acts as a source.
- When is a disease a zoonose?
- A disease is a zoonose when it is carried by an animal and transmitted to humans.
- What constitutes airborne transmission?
- For transmission to be considered airborne the pathogen must travel in the air at least one meter.
- What are droplet nuclei?
- Droplet nuclei are small particles that represent what is left from evaporation of larger particles called droplets (they are airborne).
- What are examples of direct contact transmission?
- Examples of direct contact transmission (person to person) are sex and rabies (animal bite).
- What are fomites?
- Fomites are inanimate objects that transmit to host.
- Whay are aerosols listed under contact rather than airborne?
- Aerosols are listed under contact rather than airborne because they travel less than one meter.
- What are examples of "common vehicles"?
- "Common vehicles" are common inanimate intermediaries in the indirect transmission of an agent that carries the agent from a reservoir to a susceptible host. Two examples are food and water.
- Differentiate between mechanical and biological vectors.
- In mechanical vector transmission carriage of the pathogen is passive, which no growth during transmission (ex: flies). In biological vector transmission the vector acts as a reservoir where the pathogen grows (ex: mosquito).
- What is the apparent relationship between transmission rates and changes in virulence?
- There are two possible relationships between transmission rates and changes in virulence: Decreasing transmission rates favors decreased virulence-this appears true for cholera and bacillary dysentary, and
Increasing transmission rates favor increased virulence-this is hypothesized for the flu epidemic of 1918.
- Give an example of how a pathogen can be induced to evolve increased virulence.
- A pathogen can be induced to evolve increased virulence if the spread of the disease is independent of host health/survival (ex: colds/gonorrhoea, syphillis)
- Give an example of how a pathogen can be induced to evolve decreased virulence.
- A pathogen can be induced to evolve decreased virulence if the spread of the disease is dependent upon host health/survival (ex: arthropod-borne diseases/diphtheria, tuberculosis)
- How do changes in transportation and the disruption of ecosystems contribute to the emergence of new diseases?
- What are the three types of measures we use to control epidemics? Cite a couple examples for each.
- Three types of measures we use to control epidemics are 1)reducing or eliminating the source/reservoir (ex:quarantine, treatment of waste, destruction of animal reserve), 2) breaking the connection (ex: chlorination of water, pasteurization, destruction of vectors), and 3) increasing the herd immunity (ex: active and passive immunization).
- Why are biological agents effective for terrorists?
- Biological agents are effective for terrorists because they have small mass, are inexpensive, there is a delay from release to effect, the manufacture and dispersal can be low tech, and they have a strong psychological impact.
- What are the bacteria, viruses, and toxins most commonly associated with biowarfare?
- Some of the bacteria, viruses, and toxins that are most commonly associated with biowarfare are: Bacillus anthracisis, Yersinia pestis, Hemorrhagic viruses, Variola (smallpox virus), Botulinum toxin, and Staph. enterotoxin.
- What are three general strategies employed in defense against bilogical agents?
- Three general strategies employed in defense against biological agents are vaccines, drugs, and detection/intelligence.
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