In this video, we're going to differentiate between primary infections and secondary infections. What's important to note is that an infected person may actually be more susceptible to a second infection because of the damage done to their body by the first infection. Therefore, the initial infection can make a person weaker and more susceptible to a subsequent infection. Scientists refer to the initial infection as the primary infection, defined as the first or initial infection caused by a primary pathogen, such as the virus HIV or human immunodeficiency virus, which is a virus that attacks and kills human B cells or B lymphocytes that are part of adaptive immunity. Primary pathogens such as HIV are capable of infecting even healthy individuals that are not previously infected, and they will do this in a primary infection.
The secondary infection, on the other hand, is, of course, a second infection that occurs only after the primary infection. A secondary infection is caused by opportunistic pathogens, which usually do not cause disease under normal circumstances with a person who has a normal and healthy immune system. However, these opportunistic pathogens, as their name implies, are capable of taking advantage of infecting a compromised host that may be already infected with a primary infection. Thus, a person is more susceptible to a second infection by an opportunistic pathogen after they are exposed to a first or primary infection.
If we examine the image below, we can get a better understanding of this concept and how opportunistic pathogens can infect a compromised host. Notice on the left-hand side, we have a healthy person who does not have an infection, and we're going to assume that this person has a normal, healthy, and active immune system. Notice that their immune system cells, the B cells, and the T cells, are very strong and ready to fend off even opportunistic pathogens that may try to cause harm. However, on the right-hand side, we're showing you a person who has acquired a primary infection, such as a person that has the primary pathogen HIV, which can lead to AIDS, acquired immunodeficiency syndrome. This is a primary infection, and HIV is able to cause a primary infection even in a healthy person. You'll notice here that this person has a primary infection and that they have a weakened immune system, which makes them more susceptible to a secondary infection by opportunistic pathogens. Whereas before, these opportunistic pathogens could not cause harm or disease, now they are willing to take the opportunity to attack and cause harm when the individual is compromised by the first or primary infection.
This concludes our brief lesson on primary and secondary infections, and we'll be able to get some practice applying these concepts as we move forward in our course. I'll see you all in our next video.
