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01.04 Epidemiology

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Being able to educate the public about the patterns and frequency of specific diseases and helping them understand their risks is a powerful tool in the conversation about health and disease awareness.  Understanding how diseases are spread aids in disease prevention and promoting health across the population and continues to be a large factor in community health education.

Nursing Points


  1. Epidemiology
    1. Studies incidence, control of disease
    2. Identifies risk factors
    3. Function
      1. Investigates outbreaks, epidemics
      2. Establishes, designs, manages disease prevention programs
      3. Health surveillance, monitoring
    4. Triad
      1. Agent
        1. Cause of disease
        2. “What”
        3. Germs
      2. Host
        1. Carrier of disease
        2. “Who”
      3. Environment
        1. Most favorable conditions for disease
        2. “Where”
  2. Incidence v. Prevalence
    1. Incidence
      1. New cases
      2. Probability/risk
      3. Rate of occurrence
    2. Prevalence
      1. Total number of people affected
      2. Existing cases
      3. Spread
  3. Morbidity v. Mortality
    1. Morbidity
      1. Having a disease
      2. Can have more than one
      3. Comorbidity
    2. Mortality
      1. Death
  4. Epidemic v. Pandemic vs. Endemic
    1. Epidemic
      1. Local spread
      2. Example: Zika
    2. Pandemic
      1. Worldwide spread
      2. Example: TB
    3. Endemic
      1. Permanent existence
      2. Regional
      3. Example: malaria
  5. Relation to Community Health
    1. Job of nurses
      1. Educate the public/promote awareness
        1. Diseases
          1. Risks
          2. Behaviors
        2. Prevention
          1. Precautions
          2. Self-care
          3. Health fairs
          4. Free screenings
          5. Written information

Nursing Concepts

  1. Health Promotion
  2. Patient Education
  3. Evidence-Based Practice

Reference Links

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Video Transcript

Video Transcript

Hi guys! Welcome to the lesson on Epidemiology. So understanding how diseases spread is a pretty important factor in educating the public on prevention. In this lesson, we’ll talk about how that works and we’ll also clarify some commonly misused terms in health. So, let’s go ahead and get started.

So why are we talking about epidemiology in a community health course? Well, it studies the incidence of diseases and it helps determine our risk factors. Epidemiology also investigates outbreaks and is responsible for health maintenance and surveillance. For instance, if there’s another Ebola outbreak epidemiologists are the ones who study the trends and the populations affected so people can be warned about what to avoid and how to protect themselves. This is done with the goal in mind of preventing further spread and maybe getting rid of the disease altogether.

What is an epidemiological triad? It pretty much lays out the concepts of how diseases are cultivated and spread. So we’ve all seen these words at some point in school but they can be confusing sometimes so let’s go through them. The agent is the “what” in the triad. It’s the cause of the disease. We call them germs. These are bacterial, fungal, viral. So let’s take meningitis for example. It can be either viral or bacterial. Either one will be the cause of the actual disease. We are always using hand sanitizer and hand washing to prevent the spread of germs. In a nutshell, we are trying to wash away the agent. So the host is the “who”. Who is throwing the party? This is either humans or animals. Now bear in mind the host doesn’t always have to show symptoms. They don’t even necessarily need to be sick. They just need to pick up the agent and drop it off somewhere else. Next is the environment. This is the “where”. The environment can provide the most favorable conditions for a disease to reproduce. Let’s think about the party again. The best parties I went to in high school were the ones that the most people went to and where no one ever left the dance floor. It was a sign that the host was popular or well liked. Well, germs do the same thing. They love a good party thrown by an awesome host in the right place.

So there are words we use a lot when we talk about diseases and outbreaks and sometimes they get used incorrectly. Incidence and prevalence might be the ones I’ve seen mixed up the most. So incidence tells us the new cases for a disease over a set period of time. So for instance, we are coming toward the end of flu season. We give vaccines every year to help prevent the incidence of the flu. What did I just say? We encourage flu shots to prevent new cases of the flu from popping up and spreading. Prevalence on the other hand tells us the total number of cases at a point in time. This gives us an idea of how widespread it is. So we’re in jail. There’s a population in the jail that has a virus and has been quarantined for the last week. That population grows because we keep adding to it for everyone that starts showing symptoms. The incidence are the ones we keep adding. The prevalence is the entire group. We use these to determine risk factors and any other commonalities the people affected have. 

Another pair of words people confuse sometimes is morbidity and mortality. We say something sounds morbid and we relate that with deadly. No judgment if you’ve thought it because I have too. But here’s how we should really be looking at it. When we say morbidity we mean having an illness. There’s also this thing called a comorbidity. I’m sure you’ve heard this at some point as well. Comorbidity means there multiple diseases in one person. So the person with hypertension, COPD, kidney impairment and glaucoma has several comorbidities. It is possible to have just one morbidity as well. Either way, this can be treated where mortality can’t because, very simply means death. Now FYI, we talked very briefly about mortality being a measurement of health in the community in the introduction lesson and here it is again. We use the number of deaths in a specific area to help determine the needs of that community as well. 

So these right here confuse everyone, including me. The difference between epidemic, pandemic and endemic. The easiest way to go about trying to remember each is the root of the word. “Demic” is a population. Just wanted to throw that out there so you understand how the root will change the meaning of the word.  “Epi” means around or upon. So an epidemic is a disease outbreak that spreads around an area. Remember Zika? It just happened maybe a year or so ago. Pregnant women were discouraged from travelling outside the US because it could cause birth defects. And it was one of those weird ones that spread through a specific species of mosquitoes and sex. Anyway, that was an epidemic. It spread over a short period of time within a small population of people and then it was gone. FYI though, epidemics don’t have to be contagious. We refer to opioid abuse and obesity as epidemics also. Now “Pan” means all inclusive. So a pandemic is an epidemic that has spread worldwide.  And it’s not discriminating. It’s going to be every man for himself and no one is safe. HIV and TB are huge pandemics. Think about all the screenings we have to go through if there’s a chance of exposure. There’s no rhyme or reason to who these diseases affect but they have to be infectious diseases. So last but not least are endemics. “End”..self-explanatory. So an endemic disease has taken up residency in a specific region and there’s always going to be constant worry about someone catching it. So malaria is a good example. It’s not much of a concern here, but in certain parts of Africa it’s something to look for. It’s basically the endpoint or the resting place of that disease. The disease likes something about that area where it’s allowed to grow.

So how does this all relate to community health? Well back in the Introduction lesson we said that the goal of community health is to promote and protect well-being. And then we said the job of a community health nurse is to educate the community and promote awareness right? So let’s think about this. We just talked about epidemics and pandemics. These are not words we want to use very often. So we want people in the community to be aware of how their choices and behaviors can make them more susceptible to disease and then we are telling them how they can prevent it all from happening. We hold health fairs to raise awareness and demonstrate how to self-assess for some diseases. We have free screenings for some diseases for those who may not be able to afford regular screenings. We print out pamphlets and flyers to promote healthy lifestyles and also on the flip side, let the public know what to look for with regard to infectious diseases, like, measles for instance. That’s back now, right? So epidemiology as strange as it may seem, has an impact on how the community receives information, but it also directs our education plans.

So a few key points to review. Understanding the epidemiological triad means understanding what the agent, host and environment are and how each contributes to the spread of disease. Incidence versus prevalence is the rate of new cases occurring versus the total number of people affected by a disease. Epidemic, pandemic and endemic describe for us the actual degree of the spread of a disease. We include each of these concepts when we discuss specific diseases and illnesses with our patients, so be sure to know the differences.  And now the biggest takeaway is how this all ties in to community health. We want people in the community to be aware of their risks for diseases and what to do to prevent them. We especially want them to pay attention to what’s trending and provide them with the most accurate information to promote continued well-being. 

So that’s it for epidemiology. Make sure you check out all of the resources attached to this lesson. Now, go out and be your best self today! And, as always, happy nursing!