It's Atomics question, by far the dominant part off medicine.

So when this college was founded, medicine was very largely infectious diseases, and they're broadly divided into endemic diseases, diseases that is there all the time, in the background of which there were very many during Thomas questions lifetime over the top of which occur epidemics where you suddenly get a surge off a particular infection.

And during his lifetime, there were many epidemics that we know about almost certainly many epidemics we do not know about.

So the worst example to moderately sized plague epidemics here in London, a syphilis epidemic that really occurred throughout his entire lifetime on in many ways come to an end till the beginning of this century of the last century.

Rather, a smallpox epidemic on the background of ongoing smallpox typhus epidemics on a disease that was considered pretty unique to the UK, UK the English switch sweating sickness, which of which there were two major outbreaks in his lifetime.

So there were very many epidemics at that stage.

Now play of which is to say he had two epidemics in his lifetime is an example off the extraordinary power infectious diseases have historically had to shape human history, but also the human capacity to respond to those diseases.

Exact estimates are obviously difficult on dhe views, very, but I think most people who've looked at this consider that play reduced the world's population during one that some of its bigger pandemics from the estate mated.

450 million to around 350 million, Uh, maybe slightly more than that in the 14th century and astonishing drop in global mortality on Europe, which was very badly affected.

Between 30 and 60% of the European population died.

The impact of that on society clearly cannot be exaggerated.

The risk of a plague epidemic or pandemic now significant one is now zero, although epidemics will come back to occur to this day.

This is a, however, also the Centenary year on the Centenary month off the last really serious global pandemic on that was the 1918 20 h one n one influenza pandemic, also known as the Spanish flu.

This probably killed between 50 and 100 million people.

And to put that in some kind of perspective, I've just showed the death toll in the United States, where the data reasonably reliable, comparing the number of people who died in that flu pandemic in the U.

S.

A.

With all the people who died in every war in the last century in the US, more people died in that single pandemic than everybody in the U.

S.

Who died in every war first World War, Second World War, Vietnam and career.

That puts in perspective quite how serious this was.

And as I say, there are people living today who lived through that pandemic.

These kinds off and athletics and pandemics can come on extraordinarily suddenly on spread very rapidly.

So let's take that 1918 pandemic and I'm taking the USA because we combine good data on large geography.

Looking at this map we have here on the screen, what you can seem dark colors are the area where this end of the United States on spread before September, the 14th off that year.

This is exactly 100 years ago the areas in the light colors, most of which are relatively remote but where it's had got to after October the fifth, so that spread across the USA occurred in a period when there was very much limited transport just after the war, over the period of less than a month.

And if you look at the spit spiking mortality we saw in that year, comparing the October of that year to the October off the years previously and this these were the years of privation, this is during the war, you can see the massive impact that had immortality just in this month of October, exactly 100 years ago.

So when really serious pandemics happen, they slam into society with extraordinary force and speed, and they were doing this even in pre industrial times.

So you think about play or the epidemic of syphilis, which was really developing during Thomas's lifetime, that this is, for example, a map of plagues spread on.

What you can see is that it spread really quite rapidly across Europe in the medieval period, when transport was considerably slower than it is now they're not a slightly think people make.

Imagine on, for example, syphilis, which was as far as we can tell.

A new disease to Europe around 14 94 spread after battle the Naples all around the continent, probably within a matter of months.

And it is certainly recorded as far north as leaf, for example, by 14 97.

So these diseases could spread even in periods when transport was much slimmer.

So it's therefore possible but wrong.

But many newspapers make this point wrongly s.

I'm gonna make it for them and then say it's wrong that we're increasingly vulnerable to epidemics because off the massive transport networks we have by land, sea and air.

This is just a map off the transport links in the world.

How many places you can get to within 24 hours on, as you can see, the United Kingdom?

Is that right in the center of this?

However, the reason that this is not actually a worrying as it looks, is that being rich as a society massively hardens society against epidemics off any sort.

And it does this not primarily for reasons of medicine which will come onto the Mets and does play a role.

But in fact, because of all the other things that lead to a successful rich society agriculture, for example, leading to substantially better nutrition engineering, leading to better housing, sanitation, clean and plentiful water and clean a heating as examples.

So there are many things we do societies which are not designed to prevent epidemics, but do so just as the process as countries become wealthier and more developed.

But that doesn't mean that epidemics have gone away far from it.

I put up here just six, and there are very many others.

I could have chosen just six off the epidemics that have occurred in this year 2080 in the top pro.

I've shown three, which would have been very well known to citizens of London at the time.

The foundation, this college.

There's a significant outbreak off multi drug resistant typhoid in Pakistan of cholera in Zimbabwe and Yemen, or come back to Yemen, kind of play in Madagascar and we're just about to enter plague season now.

So I'm anticipating a second plague epidemic that they're quite frequently and on the bottom row, some diseases that were not known in the time off so gruesome protective Thomas in London but are quite wide spreading a dis point in time.

A monkey pox outbreak in Nigeria.

Had this happened in London at that stage, people would have assumed this is smallpox.

They look almost identical.

Have actually bean now three cases this year in the UK, which is spillovers from that theme, er's Middle Eastern Corona virus outbreak.

That's occurring particularly in Saudi Arabia.

A real worry to people because of people becoming very crowded during the hajj and other pilgrimages and then scattering hat to the four corners of the world, often to places with relatively limited health service's on dhe at two a bola outbreaks that have occurred in in DRC this year, one of which is still ongoing and there are many others.

So the point I'm making on this is that epidemics occur every year in every continent and they kill people.

That's a societal impact will depend on many factors.

They will depend on how many people and who is affected, and it may be certain societal groups who are more important for society's functioning.

They're not more important to their families.

For example, the great flu pandemic of 100 years ago, particularly who was mortality in people of young working age.

So the impact on society was very considerable.

All flew 10 secure, the very young and the very old.

This also picked out people of young working age on many pandemics, and I'll come on to an example of this later tend to pick out people.

Your health care workers making the response are considerably more difficult, and I've given example from Nigeria.

This is just an outbreak.

The index case is not a health worker at all.

The next cases in blue are all health care workers, doctors or nurses, and all the ones boarded in red went on to die.

So being a health care worker in an epidemic or pandemic can be a hazardous occupation.

Epidemics cause substantial panic.

Andi have a substantial social and economic impacts, very often way out of proportion to their actual medical importance.

So let's take several off the recent epidemics and you'll recognize many off the front pages of the newspapers involved.

He's tended to dominate the news for very long periods, including in countries which had almost zero chance off significant onward transmission leading the U.

K Let's take saws between November 2002.

In July 2003 the SARS outbreak, which dominated the news for quite a long period of time, caused just under 10,000 cases on just under 1000 deaths in 37 countries.

Now that is obviously a substantial tragedy for the individual families, but this is a small effort out outbreak.

This outbreak, which we happen to know the data because the World Bank have looked at it, probably wiped around $40 billion off the world economy because it closed on airlines on led to panic in the particularly in Southeast Asia and Canada.

A massive influenza pandemic would be a lot bigger than that by many factors and will undoubtedly have a really serious societal impact.

So these can have a very big impact on society even if they are medically relatively less important.

The first question I'm invariably asked by ministers is Why can we not predict epidemics and prevent them before they start?

And the answer to that is they come from almost every direction.

Predicting and trying to prevent epidemics before they begin is extremely difficult and lots of people have tried and lots of people have failed.

And this is really because the great majority of new epidemics come.

Richard, News of the world come when a disease which is in an animal species, jumps over to humans.

And I've just taken a few animals here.

Thes friendly fruit bats are a source of Ebola.

This gentleman here or one of his relatives source of HIV, uh, nose the inside and in the Middle East theme Mexican pig flu, which many of you remember on B sc.

So in the great majority of new pandemics that a new to the world animals is where they come from.

But nevertheless being humans, we tend to blame foreigners on dhe, sometimes rather predictably so.

For example, when syphilis came to the UK, we called it the French pox, the Neopolitan pox on the Spanish box, depending who we dislike.

Most of that stage people talked about English sweating sickness on DSO on and Spanish flu and so so blaming foreigners is what we tend to do.

Actually, animals is where they tend to start.

But although the first reaction is almost injury, panic epidemics actually can be addressed systematically and The rest of this talk is about how systematically you can go through a new epidemic and say, Now, what are we gonna do?

And how we gonna respond?

Depends really on five things.

The first is mortality or severity off the disease.

A trivial infection is probably not something which is going to require such a major response.

The second question is easier treatment available and if not, can we find one very quickly?

Third question is, is there a vaccine available and then two very important things which are more actually illogical.

But actually the key thio any epidemic where the answer to the last things that treatment or vaccine available already is critical.

The force of transmission, which is a mathematical concept.

But I'm glad to say an incredibly simple one.

And the route above a ll the route of transmission.

The route of transmission is the key to controlling an epidemic.

Just before I go into the main technical bit off the talk, I just want to make three definitional things.

An endemic disease is the background rate of an infectious disease in the making these definitions cause I will use these terms repeatedly, and I want to be clear what they mean.

It maybe zero.

So an epidemic, maybe monkeypox.

A relatively small number of cases.

But the normal number is zero.

Or it may be a quite a high number, which, actually, then you have a peek off if you think about.

For example, pneumonia.

Pneumonia is an endemic disease in the UK It kills very many people in the UK probably 29,000 people a year on average.

But we don't consider that an epidemic.

It's just there the whole time.

Whereas we get much more excited about epidemics which killed much smaller numbers.

So endemic diseases can be quite serious, and I'll be talking for most of the rest of this series on endemic diseases.

And then you have outbreaks or epidemics, and that's when you have a spike off diseases above the seasonal background.

You may be a small spike for seasonal background is almost zero where it may be a large spike, and the terms are slightly slippery.

But in general, people mean an epidemic to mean quite a large outbreak and an outbreak to mean a geographically localized one.

So I'm going to use those terms that way, there's you could get a bit panicky about our use him and finally a pandemic.

He's an epidemic which occurs worldwide, or at least cross is a lot of international boundaries on Officially, it's declared by the World Health Organization.

So the first of the things I said is we're important is mortality and mortality varies very substantially by different epidemics.

But of course it has to be to have an impact.

It has immortality multiplied by the number of people who actually have it.

So let's start off with a bola recent about epidemic, the mortality for a Buddha epidemic with somewhere between 60 and 70% if you've got the disease.

That was the probability of dying smallpox, the major former smallpox.

Around 30% of people would expect normally to die.

You think about the H one n 1 1918 flu pandemic, but that only had a mortality rate of about 3%.

But because it affected many millions of people, its impact on society was actually considerably greater on.

Finally, I put down a disease which really started here in the UK new variant CJD, which came from BSC that had 100% still has 100% mortality.

Um, but of course, relatively small numbers, So the mortality rate is very important.

But that may not just be a function of the disease, So you've also got the mortality may very bone nutritional status by ethnicity by age or a variety of other factors.

So if you just take measles, a disease which, wrongly lots of people think they're quite, is quite a trivial disease in epidemics of measles across Africa, for example, when they occur, you're typically yet a mortality rate of somewhere between five and 10% of all Children.

To get measles will go on to divert.

It is not a trivial disease.

Handy up thio one in 10 in measles, on the other hand, in an endemic in the UK because people are well nourished, the mortality rate for measles is around one in 5000.

Still not trivial but very substantially different, say mortality can vary even within the same disease.

This is most clear if you look about influence a looker influenza and hear.

What I've done is a table two by two table comparing for while three influenza outbreaks and the key things you need to understand is that transmission and mortality in influenza are to a large extent not related to another.

So you have some epidemics like the Spanish flu pandemic, a fairly high mortality, 3% but not massive but massive impact because it had very high transmission.