Med-Surg Immune System, part 3: Immune System Malfunction & Infection

by Cathy Parkes September 28, 2020

In this video

Hypersensitivity of the immune system

Autoimmune reactions


Chain of infection

  • Causative agent
  • Reservoir
  • Portal of exit
  • Mode of transmission
  • Portal of entry
  • Susceptible host 

Stages of infection

  • Incubation period
  • Prodromal stage
  • Illness stage
  • Convalescence phase

Risk factors


  • Systemic infection symptoms
  • Local infection symptoms
  • Which type of infected patient should you prioritize on an exam? (Systemic vs. local)

Full Transcript

In this video, we are going to talk about immune system malfunction as well as infection. If you're following along with cards, I'm on card number seven. Let's talk about the three main ways your immune system may malfunction.

One is something called hypersensitivity. This is where your immune system has an exaggerated or inappropriate response upon exposure to an antigen or allergen. So basically, your immune system is going after that antigen or allergen, and it kind of goes overboard, and it ends up causing inflammation or destruction of healthy body tissue as well.

Then we have an autoimmune reaction. This is where the body's normal defenses recognize self cells as non-self cells and target them. This may be due to genetic, hormonal, or environmental factors.

Then we have something called immunodeficiency. This is where we have an absent or depressed immune response. It could be due to an infection, medications, or genetic disorders. But basically, when the patient's immune system is not functioning at full capacity, it places them at high risk for infections.

Speaking of infection, let's talk about the chain of infection as well as the stages of infection.

So we have a causative agent. So that could be a bacteria, a virus, or some kind of toxin.

It resides in a reservoir, and that might be the human body, but it could also be something like the soil.

Then it leaves through the portal of exit, so that could be through the respiratory tract, or something like the blood.

It has a mode of transmission, so it may be transmitted through droplets, contact, or airborne.

And then it enters through the portal of entry into a susceptible host. So that's basically the chain of infection.

In term of the stages of infection, there are four stages.

The first stage is the incubation period. This is where the pathogen enters the body and starts to multiply. There are no symptoms during this incubation period.

Then we have the prodromal stage. This is where the pathogen continues to multiply, and we have the onset of general symptoms. So this may be like malaise, maybe fever, just generally not feeling very well.

Then we move into the illness stage. This is where we have the onset of specific symptoms related to that particular infection. So if it was a respiratory infection, now I'm getting the runny nose and the coughing, etc.

Then we have the convalescence phase this is where symptoms subside and eventually disappear, and you have gradual recovery from your illness.

Let's now touch on the risk factors that place an individual at higher risk for infection. These include compromised immunity, chronic or acute disease.

So, for example, if the patient has diabetes, that is a chronic illness, and it definitely places that patient at higher risk for infection.

We also have poor hygiene, poor sanitation, and crowded living environments.

So, for example, dormitories. I sent my daughter to the dorm last fall, and she had two roommates, plus a super crowded dorm. And she got so sick the first couple weeks of school because her immune system is basically just overwhelmed with all those other people and all of those germs. After the first couple weeks, her immune system kind of caught up and got a little tougher, and she's been healthy since. But those first couple weeks were kind of brutal.

Other risk factors associated with infection include IV drug use as well as unprotected sex and impaired skin integrity.

Then the last thing I want to go over here are the differences in symptoms between a systemic infection and a local infection.

So a patient with a systemic infection will have symptoms such as fever, malaise, chills, fatigue, tachypnea, and tachycardia.

If we are talking about a local infection, so just an infection on one part of the body, then symptoms will include edema, pain, erythema, which is a fancy name for redness, decreased function, and warmth in a particular area of the body.

So as you are answering exam questions and need to prioritize a patient, if you have one patient who has signs and symptoms of a systemic infection and another patient who has signs and symptoms of a local infection, you always want to prioritize your systemic infection patient first.

Okay. So hopefully, this video has been helpful. When I come back, we will talk about diagnostic tests that relate to the immune system and how to determine if a patient is fighting an infection, if they have inflammation in the body, that type of thing. So stay tuned, and I'll see you soon!

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