What is epidemiology?

As I said that this blog is going to share with you what I learned in epidemiology, so the first topic would be the very basic concept: what is epidemiology, exactly?

What is your answer to the survey question at the very beginning of my blog? The answer should be all of them. Did you get it right? I have to be honest with you. Before taking this course, I thought epidemiology included only the first two areas: study of distribution and determinants. Based on the text book, it also includes applications. [1 (page3)] 

Additionally, before learning this course, I thought epidemiology was a very light job, because I only thought of epidemiology when some outbreak of certain disease happened. After learning the basic concepts of epidemiology, I realize that there are three different types of prevention, which include primary prevention even before something happens, such as immunization. [1 (page6)] Therefore, epidemiology is actually an underestimated job, because if no outbreak happens, their efforts are easy to be ignored by population; while if outbreak happens, people always blame them...

Based on the epidemiology triangle (Figure 1) below from the textbook, any epidemiology events are caused by interaction of the host (mostly means "who" gets the disease), an infectious agent (mainly means "what" causes the disease), and the environment factor (normally means "where" the disease occurs). The vector is a media which transmit the disease. [1 (page19)] Let's use tuberculosis as an example, the host would be human, the agent would be bacteria that causes TB, and the environment would be unsanitary environment. The vector should be air, because it spread by air when TB patients cough or sneeze. [2]

Figure 1. Epidemiology triangle 

Also, I learned how to determine and investigate a outbreak. Firstly, if a disease exceeds its normal frequency of occurrence, we consider it as a epidemic disease. Secondly, we need to figure out how long its incubation period is by interviewing people and figure out the specific group. Thirdly, calculate the attach rate in order to get an idea of what determinants are. Lastly, come up some recommendations for controlling and preventing this disease. [1 (chapter2)]

But I am still confused about whether epidemiology is only dealing with infectious diseases. Does it also include other non-infectious diseases, such as diabetes?

Reference:

1. Gordis L. Epidemiology. 4th ed. Elsevier. 2008. ISBN: 9781416040026
2. Konstantinos, A (2010). Testing for tuberculosis, Australian Prescriber. 33 (1): 12-18.