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Flu shift and drift

Learn how Type B Influenza virus has genetic drift, whereas Type A Influenza virus has genetic drift AND shift. Rishi is a pediatric infectious disease physician and works at Khan Academy. These videos do not provide medical advice and are for informational purposes only. The videos are not intended to be a substitute for professional medical advice, diagnosis or treatment. Always seek the advice of a qualified health provider with any questions you may have regarding a medical condition. Never disregard professional medical advice or delay in seeking it because of something you have read or seen in any Khan Academy video. Created by Rishi Desai.

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  • leaf yellow style avatar for user ♦SamuelM♦
    Would the Swine Flu (H1N1) that happened at around 2008-09 be considered a pandemic?
    (11 votes)
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  • blobby green style avatar for user Reg Pollock
    Where can we go to find out which strain is in the population?
    (2 votes)
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  • blobby green style avatar for user Jackie Schwartz
    In a previous lecture you described a genetic shift as the creation of a new subtype (H1N1 and H3N2 infecting the same vessel and creating H1N2). If a genetic shift is responsible for pandemics, then why was the swine flu (H1N1) in 2009 a pandemic? Since H1N1 is what commonly affects us now? Was this the offset of it?
    (1 vote)
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    • leafers ultimate style avatar for user William H
      H1N1 was the result of the fact that pigs have receptors that can bind to both avian and human flu viruses. These most likely both went into the same cell in a pig and combined, and were eventually transmitted to a human carrier.
      (2 votes)
  • primosaur ultimate style avatar for user nickeldime88
    Where are all the numbers on the graph?
    (1 vote)
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  • purple pi purple style avatar for user eddieqiao
    could that auctully happen in real life
    (1 vote)
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  • duskpin ultimate style avatar for user Sally
    Which part of the world is the flu mostly in.
    (1 vote)
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  • female robot grace style avatar for user Anna
    I have heard of a person who already had the human flu virus getting avian flu and then the 2 viruses mixing to form a totally new flu virus that nobody has been exposed to.

    Also those flu vaccines can be harmful because the people who produce it will look for profit and not safety and so this flu vaccine can weaken your immune system. Thus it is better to get the virus itself. Wouldn't you agree with that?
    (0 votes)
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    • leaf green style avatar for user Nahn
      Humans cannot act as a mixing vessel for avian and human influenza because avian influenza cannot really infect humans directly (unless you exposed to massive amounts of avian influenza, and even then its unlikely that you would be able to spread that avian flu to another person). What you are referring to is when a avian influenza and a human influenza virus both infect a pig, and then there can be genetic shift within that pig (the mixing vessel) forming a totally new strain of human influenza that we have not seen before. This can be very dangerous, and can cause flu pandemics.

      Its true that flu vaccine manufacturers do profit from making the influenza vaccine, but that in no way means that the manufacturers don't care about vaccine safety. As far as medications go, there no other group of drugs or medical treatments anywhere that have been as well studied or that have as strict of safety regulations as do vaccines. As for getting the virus itself rather than the vaccine, definitely not better. Assuming that you did not die from getting a strong strain of wild influenza (Most healthy adults would be fine and just be sick for a few days, but infants, elderly, or immunosupressed might not) you would only be protected against getting that exact same strain of influenza again, as compared to the 3 to 4 strains of influenza that you would be protected against if you had gotten the vaccine. It is true that if you got really sick from a specific strain of influenza, you would be protected for longer against that specific strain of influenza in the future, but the protection you get is only for that specific strain. If next year, a different strain of influenza happens to be the one that you come across, you are left with no protection at all ( after having to go through being sick with the flu the previous year!) So its better to get protection against the 3 strains of influenza that you are likely to see each year, than it is to get sick for a few days and then have really long lasting protection against a strain that you probably never going to come across again anyways.
      (5 votes)
  • piceratops ultimate style avatar for user nobody
    isn't shift like what they say, there is a new flu every year
    (1 vote)
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    • hopper cool style avatar for user SofiyaMarkova
      shifts create drastic changes so, yes, it is counted like a new type A flu. drifts still create a form of a "new" flu, it is just that the change is due to a mutation of the same one rather than a mix of 2 other ones, so it is not as drastic.

      "Antigenic shift is the process by which two or more different strains of a virus, or strains of two or more different viruses, combine to form a new subtype having a mixture of the surface antigens of the two or more original strains."

      source: https://en.wikipedia.org/wiki/Antigenic_shift
      (0 votes)
  • male robot hal style avatar for user 施志雄
    If it were impossible for two different strains of a virus to attack the same cell would it then be impossible for a virus to shift/drift? Or is it possible for a strain of type A flu to genetically change/mutate without mixing with another?
    (0 votes)
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    • female robot grace style avatar for user Anna
      It is possible for multiple viruses to infect one cell. Then it would be possible for it to shift and drift. Genetic drift is basically mutations. Genetic shift is changing of DNA or RNA segments from one type to another type.
      (1 vote)

Video transcript

Let's say there are two communities, an orange community and a purple community, and they're separate from each other. And your job is to go into these communities, and find out what the most common influenza type is that's circulating among the people. So you do this, and the first thing you discover is something that's pretty interesting, which is that, in the orange community, turns out that they really only have influenza Type A. Remember that there are three types of influenza, and, over here, the only one that seems to be affecting people is Type A. So let me actually write that over here, Type A. And if you go over to the purple community, you actually find quite the opposite. You find that over here, people are also getting the flu, but it's always because of Type B. So these people over here are having influenza Type B. And influenza Type B also has eight strands of RNA. And let me write in purple then, Type B. So that's what you learn in the first kind of day on the job. Now there are many different types of Type A that are affecting the orange community, and what I've drawn for you is just the dominant strain. So there may be a handful of Type A's affecting the orange people, but this is the dominant strain. And you know, actually the same is true over here in the purple community. They have a few different Type B's circulating, but the dominant strain is the one that I've drawn for your. So now, let me make a little bit of space, and let me tell you what you're going to have to do. Over the course of the next year, over the course of the next 12 months, you're going to actually have to follow these two communities. And what you're going to do is basically track out over that year what's happening with the dominant strain. So that's all we care about-- not all the strains, but just the dominant strain. And you want to know how genetically different is it compared to what it was like on day one of your job? So when I say genetic change, I'm really comparing it to what it was like on the first day of your job-- comparing to initial strain. So, over the 12 months, you'll get a real good idea of how much change happened while you were on the job. So let's say you start out, and you live close to the purple people. So, of course, initially, there's no change. You're doing the Type B strain, and you're saying, well, yep, it hasn't changed yet. But some time passes. Let's say you spend some time away, and you come back, and you visit the purple community. And you ask them, hey, what is the common Type B strain that you guys are seeing nowadays? And they say, well, it's basically the same as it used to be, it hasn't really changed a lot, but there are two point mutations that have happened. So the dominant strain now has a couple of point mutations, so it's a little bit different than it used to be. And you say, a-ha, there is some genetic change happening here. The dominant strain is changing a little bit. And then you go, and you visit again sometime later, and they say, yep, thanks for visiting again. A couple more changes have happened since you last were here. And you say, ah, interesting. Let's plot that a little bit higher. So now the virus, the Type B virus, is looking slightly different from how it was when you first started the job. And you keep going with this process, and you know, there's a mutation here, another one over here. So mutations kind of pile up. And basically what you get is kind of a staggered line-- something like this, where it kind of goes like that, all the way to the end of the year. So the end of the year comes, and you look back at your virus, and you say, ah, there are a few mutations. It's a little different than what it was like when I started. And those little mutations you can see with the yellow x's. So what would we call this process? We call it genetic drift. This is genetic drift. This is kind of the normal process that happens with many, many types of viruses and bacteria. Really all viruses and bacteria make mistakes when they replicate, and so you're going to see some degree of genetic drift over time. So now here's the cool part. You go to the orange community, the orange county, if you want to call it that. And you say, hey, I'm here to do the exact same thing with your Type A influenza virus. And, in the beginning, of course, it's not any different. But you come back a little bit later, and you notice that this one has had a couple of changes, a few mutations, just like you saw before. So you say, OK, well, so far so good. It looks like it's a little changed. And then, you find out that, you know, there's one more mutation, when you come back on another trip. So you say, OK, looks like it's a little changed further. And then, a really interesting thing happens. What you find out is on a third trip, that this entire segment is gone, and it's replaced by this. So you see a huge, new chunk of RNA. So how do you plot that on your genetic change axis? Well, it's really different, isn't it? So you'd say, OK, well, gosh, now that 1/8 of the entire thing is different, that would be something like this. That's a huge jump. So you'd say, OK, well now there's been a huge genetic change. And then, you come back on another trip, and you find out that there's a little mutation in this green RNA, and maybe one over there. So, again, you've got a little bit of change. And you go, and you find out that there was another mutation here, maybe one over here. And so, you keep plotting-- you're very loyal to your job-- you keep plotting. And then, it turns out that there's another big shift. Let's say this piece gets changed out for this one. And so, again, you have a big, big jump. Something like that. And finally, by the end of the year, it kind of goes up again, because you've got a couple more mutations. So let's say, there's another mutation there and there. So that's what it looks like. Right? The genetic change over time for the orange one, the Type A, is actually looking quite different. And this one actually has elements of what I would call genetic drift and shift. And, more specifically, this part would be kind of a big shift. This is where a whole chunk of RNA got kind of incorporated into the dominant virus. These are two shifts that might have happened that year. And these other parts-- let me circle with a different color, let's say, over here-- this and this is actually looking more similar to what we talked about before. These are just kind of steady changes, steady mutations over time. And this is kind of what we have come to know as genetic drift. So with Type A influenza, done in orange, you can see that there is some drift and some shift happening. And with Type B influenza, there's only genetic drift. Now what happens, and this is kind of the scary part about Type A influenza, is that whenever you have these giant shifts, there are two here, whenever you have these shifts, the entire community hasn't really experienced that new Type A influenza. They're not used to it. Their immune systems don't know how to deal with it. And so, many, many people can get sick. And what we call it is a pandemic. So in the past, we've had a few pandemics. And each time, it's usually because of a big genetic shift that happens, and many, many people, as I said, get sick, go to the hospital, and can even die.