Ch.2 Dynamics of Disease Transmission Flashcards
How does disease begin to arise within a population?
Disease begins to arise within a population as a result of interaction between the host (a person), the agent (bacterium), the environment (contaminated water source), and in some instances of disease can also involve a vector (mosquito) in order to transmit disease. although some diseases are largely genetic in nature they do involve some degree of balancing with these factors, that causes the host to become susceptible to the disease.
What are some of the basic factors that can determine the susceptibility to a particular disease?
Host susceptibility is determined by a variety of factors which include genetic background, nutritional diet intake, and immunologic integrity of the host with both natural infection and immunization.
True or False: The Factors that can cause disease include biological,l physical,chemical, and stress.
True
How can diseases be transmitted and how does this affect its prevalence within the population?
Diseases can be transmitted directly (person-to-person) or indirectly (vehicle transmission; single exposure, continuous exposure, multiple exposure, or through a vector) and thus different organisms and disease may spread in different ways depending on the characteristics for rate of growth and route of transmission including other virulence factors that increases its risk of survival within a population.
Explain the difference between clinical and subclinical types of diseases that exist.
Clinical Disease is characterized by signs and symptoms that typically arise as the result of disease.
Nonclinical (Inapparent) Disease is composed of 4 types; preclinical, subclinical, persistent (chronic), and latent disease.
1) Preclinical- disease that is not clinically apparent but is determined to progress into disease.
2) Subclinical- Not clinically apparent and is not destined to become clinically apparent
3) Persistent (Chronic)- An infection that is present for years, that can at times last for a lifetime.
4) Latent- Infection with no active multiplication of the agent; where only the genetic information is present in the host and not the viable organism.
What is the iceberg concept and how does it pertain to the importance of epidemiology?
The iceberg concept is important because it discusses that is not efficient to count only the clinically important cases that we see; as only clinical cases are the readily apparent cases readily see. As the severity of the disease appears to be related to the virulence of the organism and to the site of the body. In which the organism multiplies and must be appreciated to understand how the disease spreads from individual to individual in order to cause disease within the population.
Carrier Status refers to what?
Carrier Status is an individual who harbors an organism, but is not infected as measured by serological studies (no evidence of an antibody response) or clinical illness. Although, they can still infect other individuals regardless.
Describe the difference between an epidemic,endemic and pandemic.
Pandemic- is a worldwide epidemic
Epidemic- the occurrence in a community or region of a group of illnesses of similar nature, clearly in excess of normal expectancy and derived from a common or propagated source.
Endemic- the habitual presence of a disease within a specific geographical area.
During a single common vehicle exposure what are the typical characteristics that are displayed within the population?
1) Explosive (rapid # of cases arise within the population)
2) Limited to those who have a common exposure.
3) Food-bourne illness rarely occurs in persons who acquire the disease from a primary case.
What is common vehicle exposure?
An instance in which the all the cases that had been developed were exposed to the factor in question. Where the exposure itself can be single, multiple , or continuos.
What are the determinants of disease susceptibility within a population?
What determines the disease susceptibility within a population is is the balance between the # of susceptable individuals and the # of non-susceptible (immune) individuals. Thus, when this balance is disrupted and moves towards more susceptibility then the likelihood of an outbreak increases.
Define Herd Immunity
Herd Immunity- is the resistance of a group of people to an attack by disease, to which the large portion of the members of the community are immune to.
How does herd immunity protect others within the community and decrease the likelihood of disease transmission and thus prevalence, and how can we achieve it?
We can achieve herd immunity through vaccination in order to increase the immune status of the entire population and decrease the chances of it coming into contact with susceptible individuals. Thus, interrupting the transmission of disease even if not everyone is immune, so long as a critical percentage of the population is.
What conditions must be met in order for herd immunity to exist?
1) Disease must be restrict to a single host species
2) Transmission must be relatively direct from one member of the host species to another .
3) Herd immunity operates optimally under the theoretical pretenses that the community continuously mixes together
*If a reservoir outside of the human host exist, herd immunity will not operate as other means of transmission are available.
The interval from which the recipient of infection to the time of the onset of clinical illness; where no sign of illness is present is known as what?
The incubation period
- The precise incubation period does not exist for a particular disease rather, a range of incubation periods is characteristic for a disease to develop.
