BIO 550 Week 2 Discussion Questions
BIO 550 Week 2 Discussion Questions
DQ1 Describe or illustrate the modes of transmission of communicable disease in a population. What knowledge should you take away from this information?
DQ2 Are host, agent, and environment equally important in the natural history of disease, or is one feature more critical than the others? Justify your reasoning.
By contrast, the numbers affected by some communicable diseases can undergo a sudden increase over a few days or weeks, or the rise may continue for months or years. When a communicable disease affects a community in this way, it is referred to as an epidemic. Malaria is endemic in some areas of Ethiopia, and it also occurs as epidemics due to an increase in the number of cases suddenly at the beginning or end of the wet season.
1.1.3 Prevention and control measures
The health problems due to communicable diseases can be tackled by the application of relatively easy measures at different levels of the health system. Here, we will use some examples at the individual and community levels, which are relevant to your work as a Health Extension Practitioner.
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Some measures can be applied before the occurrence of a communicable disease to protect a community from getting it, and to reduce the number of cases locally in the future. These are called prevention measures. For example, vaccination of children with the measles vaccine is a prevention measure, because the vaccine will protect children from getting measles. Vaccination refers to administration of vaccines to increase resistance of a person against infectious diseases.
Once a communicable disease occurs and is identified in an individual, measures can be applied to reduce the severity of the disease in that person, and to prevent transmission of the infectious agent to other members of the community. These are called control measures. For example, once a child becomes infected with measles, treatment helps reduce the severity of the disease, and possibly prevents the child’s death, but at the same time it decreases the risk of transmission to other children in the community. In this context, treatment of measles is considered a control measure.
- Later in this Module, you will learn that the widespread use of insecticide-treated mosquito nets (ITNs) is recommended as a prevention measure for malaria, which is transmitted to people by mosquitoes. If you promote the effective use of mosquito nets in your community, how would you expect the number of malaria cases to change over time?
Next we look at the main ways in which infectious agents are transmitted.
1.2 Factors involved in the transmission of communicable diseases
Transmission is a process in which several events happen one after the other in the form of a chain. Hence, this process is known as a chain of transmission (Figure 1.1). Six major factors can be identified: the infectious agent, the reservoir, the route of exit, the mode of transmission, the route of entry and the susceptible host. We will now consider each of these factors in turn.
Tables 1.1 and 1.2 referred to Plasmodium falciparum as an infectious agent causing malaria. This is an example of how infectious agents are named scientifically, using a combination of two words, the ‘genus’ and the ‘species’ names. The genus name is written with its initial letter capitalised, followed by the species name which is not capitalised. In the example above, Plasmodium is the genus name and falciparum refers to one of the species of this genus found in Ethiopia. There are other species in this genus, which also cause malaria, e.g. Plasmodium vivax.
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