Question

1-Use your own words to explain what is meant by the epidemiological triangle to a person who does not know epidemiology. Explain the three elements of the triangle as well.

2-Use your own words to explain carrier and index case to a person who does not know epidemiology.

3- Use your own words to explain the terms: reliability and validity to a person who does not know epidemiology.

4- Use your own words to explain what is subclinical and explain why are subclinical (also called “inapparent”) diseases significant for epidemiology and public health to a person who does not know epidemiology?

5-Use your own words to explain incubation period and generation time and explain what is the significance for disease outbreak between the two to a person who does not know epidemiology?

6-Use your own words to explain herd immunity, passive immunity, and active immunity to a person who does not know epidemiology.

Answer 1

1. Epidemiological Triangle:

The popular disease model is called as  epidemiologic triad or triangle.

The triad comprises of an external agent, a susceptible host, and an environment that aids in bringing the external agent and host together.

For example in HIV diseases

• Agent. HIV virus makes human being more vulnerable to other forms of infection. Because the virus makes the host body immune compromised through direct contact through infected person’s bodily fluids, and also spread through sexual contact or shared needles.
• Host. HIV can be transmitted through open wound or the mucous membranes in oral cavity
• Environment: lower incidences of reporting due to social pressure, poverty, discrimination will discourage individuals from being tested etc.  

2. Index is the first case that is reported to have the outbreak of the disease whereas, carrier is a person or other organism that carries the infectious agent but usually does not display the symptoms of the disease.

3. Validity is used to assess/analyse the extent to which the information collected can lead to accurately answering the study queries so that the results are precise and easily conclusions can be arrived regarding a disease.  Reliability is the overall consistency of a test. A test is said to have a high reliability only when it produces a same results under similar conditions. for example if the test is repeated using a different set of group of people, same results need to be arrived.

4. The process begins after an exposure to factors which will load to disease.in a susceptible host.

For an infectious disease, the exposure is a microorganism.

For cancer, the exposure may be a factor that initiates the process

After the disease process has been stimulated, pathological changes may occur without actual manifestation of the symptoms and this stage is called a subclinical stage. During this stage, disease is said to be asymptomatic. The incubation period for hepatitis A is as long as 7 weeks. The latency period for leukemia after atomic bomb explosion in Hiroshima is 6 to 7 years