in this video, we're going to begin our lesson on acute viral infections versus persistent viral infections. And so it turns out that animal virus infections can be divided into two main categories that we have number down below one and two. And the first category is going to be acute infections and the second category is going to be persistent infections. And so acute infections are going to be infections that are characterized by a sudden onset of symptoms or the symptoms come very very quickly and over a relatively short period of time. Now, persistent infections, on the other hand, are going to be infections that are characterized by lasting for very long periods of time and perhaps even the entire lifespan of the host. And so if we take a look at our image down below, we can get a better understanding of acute versus persistent infections. And so notice that we're showing you this graph here and on the X axis of the graph, what we have is time and notice that we have time and days over here for this portion of the X axis and then we have time and months or years over here for this portion of the X axis and then on the Y axis, notice that we have the number of variants that are present or the number of viral particles that are present over time. And so what you'll notice is that the purple shaded region of our graph right here is focused on an acute infection and an acute infection, which you'll notice is that it relatively last a short period of time, just a few days at a maximum here. And what you'll notice is that the viral particles are only going to be present for a relatively short period of time before the viral particles are eliminated and they go away now over here, on the right in the green background, we're showing you a persistent infection. And with persistent infections, which will notice is that the number of viral particles is going to be steadily uh lasting for long, long periods of time, perhaps months or even years in some cases. And so um we'll get to talk a lot more about acute infections and persistent infections as we move forward in our course. But for now, this year concludes our brief introduction to acute infections, which again have a sudden onset of symptoms that last a short period of time versus persistent infections that last long periods of time, perhaps the entire lifespan of the host. And so we'll be able to get some practice applying these concepts and learn more as we move forward. So I'll see you all in our next video

in this video, we're going to talk more details about acute viral infections. And so recall from our previous lesson video that acute infections are going to be viral infections that have a sudden onset of symptoms where the symptoms appear very quickly and over a relatively short period of time. For example, just a few days now, acute viral infections are going to result in the release of viruses from an infected host cell during a popped Asus. And so some of the cells of the host cell will die during an acute infection. However the host or the human itself may still survive the acute viral infection despite the fact that some of its cells will die. And this is because the host cell's immune system can gradually eliminate the virus from the body again over a relatively short period of time. And so examples of acute viral infections include influenza, which is the flu poliomyelitis or polio mumps and Covid 19 itself, which of course the covid 19 pandemic uh, is going to be associated with acute infections. And so if we take a look at our image down below, which you'll notice as we're showing you a graph here of an acute infection. And so what you'll notice is on the X axis of this graph, we have time and notice that the time is in units of days. So we're talking about an infection that occurs over a short period of time, just a few days and over here on the Y axis. What we have is the presence of symptoms and the number of variants that are present. The presence of symptoms is indicated by the dark orange area that you see. And then the lighter orange area represents the presence of variants, the presence of infectious particles. And so what you'll notice is that upon being infected by a virus that uh is going to cause an acute infection, the virus is going to be produced uh over a relatively short period of days and at its peak is when you'll have the most amount of symptoms. So the individual have symptoms here. Uh and you can see that the Syrians or the viral particles will be present from the beginning to the end of the infection. Uh and you'll see that the host cell's immune system is able to basically eliminate the virus and over a relatively short period of time, just again within just a few days, uh, the entire viral infection can be eliminated and so the virus is going to be completely eliminated again after just a short period of time of just a few days. And that is what characterizes it as being an acute infection. And so being able to recognize this graph uh as an acute infection could be something that you could be tested on. And so this here concludes our brief lesson on acute viral infections and we'll be able to get some practice applying these concepts and then we'll talk more about the persistent infections. So I'll see you all in our next video

in this video, we're going to talk more details about persistent viral infections. And so recall from our previous lesson videos that persistent viral infections are going to be infections that can last for a very long period of time. For example, several years or even up to the entire lifespan of the host. Now, these persistent infections that last a long time can be further categorized into two groups that we have numbered down below one and two. And so the first type of persistent infection that we're going to talk about is the chronic infections and the second type are the latent infections. And so both of these are persistent infections that last long periods of time. Now, chronic infections are going to be characterized by the continuous production of viral particles over long periods of time. And so if we take a look at our image down below, over here, on the left hand side, we're showing you a persistent infection that's further categorized as a chronic viral infection. And so what you'll notice about the X axis in this graph is that the uh, X axis can go much longer here in terms of the time, it can go up to several years lasting a very, very long time. And so what you'll notice is on the Y axis. Again, we have the presence of symptoms is categorized by the dark orange area and the lighter orange area represents the number of variants that are present and so upon being infected by a virus that causes a chronic infection, viral particles will start to be produced and then there may be symptoms uh here for a short period of time. But then the symptoms may go away and uh the person may still be continuously producing viral particles. So you can see that the viral particles are still being produced at a high level for several years for many, many years. And so the variance or the viral particles are going to be produced continuously over once again, a long period of time Now for latent infections, latent infections once again are persistent viral infections, they last a long period of time. However, with latent infections, the virus is not going to be continuously produced. Instead, with latent infections, the viral genome is able to silently integrate into the host cell's chromosome uh and so uh it will not be producing viral particles during that time however, but it can reactivate later in life several years later causing a productive infection. And again, productive infections are going to lead to the generation of new viral particles. And so again the viral genome can actually integrate itself into the host cells, eukaryotic host cells, chromosomes and this creates what we call a pro virus. And so a pro virus is basically the eukaryotic version of a pro fage where again the viral genome integrates into the host cell's chromosome and the virus in a latent infection and chronic infection ultimately is not going to be eliminated. Uh as uh an acute infection would and so it's not going to be eliminated from the organism. And the symptoms can re occur later in life for a latent infection. And so notice taking a look at our image over on the right hand side, we're focusing on a persistent latent infection, viral infection and what you'll notice is upon being infected by the virus. The viral particles maybe being produced. Uh, there may be some symptoms and then ultimately the viral particles may appear to go away. But what's actually happening is the virus genome is integrating into the host chromosome silently and so it may remain silent and dormant for several years before it reactivates the virus reactivates. And the reactivation of the virus several years later can cause the viral particles to be produced. And so the virus is going to be silent uh in the host. Uh, and it's going to be reactivated at a later time. And that is what is characteristic of these latent viral infections. And so this year concludes our brief lesson on persistent viral infections, differentiating chronic infections from latent infections. And we'll be able to get some practice applying these concepts as we move forward in our course. And so I'll see you all in our next video