The making of an influenza pandemic

Published on July 11, 2013   51 min

A selection of talks on Infectious Diseases

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Hello, I'm Jonathan Van-Tam from the University of Nottingham, and welcome to this lecture called The Making of an Influenza Pandemic. What I'm going to do in the next few minutes is try and show you the basics of influenza and how we get these phenomena called pandemics that are created that are such serious threats to public health. I'm going to take you from the very basics, through to some more complicated concepts, and hopefully by the end of the lecture, you'll have a fairly good grounding in how influenza pandemics occur in nature.
Let's begin with the influenza virus itself. On the left, you've got an electron micrograph picture, and on the right you have some bullet points, which I shall go through. The first point I want to make is that influenza viruses are part of the Orthomyxoviridae family and they are RNA viruses. The important thing about an RNA virus is that when it replicates, it doesn't really check itself very well when it's making multiple copies and it has a high error rate, the consequence of that in nature is that there are frequent mutations to the virus. This will be important when we're thinking about influenza and how it changes, just store that one away and we'll come back to it. The next thing to say about influenza is that we describe three types of virus in nature, type A, type B, and type C. Now we do know that types A and B are the major human pathogens and they're the viruses that give rise to normal winter epidemics of influenza year on year, and flu A is particular in being the one that we attribute with causing pandemics. It's not really possible for influenza B to cause a pandemic, but Influenza A does and will continue to cause pandemics as we go through human history. I'll come back to that again a little later. But the final point on this slide relates to influenza C. It is an influenza virus, but it is just one of the 300 or so viruses that together give us the syndrome we recognise as the common cold. What I'm trying to say is that influenza C is not really influenza in quite the same sense as influenza A and influenza B, and in public health terms, it's really not significant. It's just one of those viruses that causes the common cold, and so in a sense, and certainly for the rest of this lecture, it can be set aside and forgotten about. Now, before we leave this slide altogether, just look again at the picture and you can see I've put a red circle on it and if you look inside the red circle, you can see some spikes sticking out from the surface of the virus. In the next slide, we'll look at a diagram and have a little drill down about what those spikes are. What is their significance?