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Hello everyone, welcome to the sessions.

The role of my presentation to discuss emerging virus and

I will focus on two viruses that have emerged in 2013.

First the Influenza A H7N9 and second the so

called Middle East Respiratory Syndrome Corona Virus.

The number of case that has been observed with these two viruses are very limited,

approximately 134 for the Influenza A viruses and

96 understand was the corona virus.

But whatever the mortality rate associated with infection is very high.

And this is the reason why we are very preoccupied to

follow the evolution of these viruses.

So in conclusion we have a limited number of case with high mortality rate, and

this explains why organization like WHO or

other else organizations care about these viruses.

And the main question is to identify whether this virus

could adapt to humans from its animal reservoir to cross the barrier of species.

And then to be really human adapted in order to cause a pandemic for example.

And this is what I will discuss today.

And for this, I will discuss of the animal reservoir of these viruses.

So we'll discuss of the diversity of these viruses.

And also I will stop few minutes on the genetic matter of

these viruses that are made of RNA, which is very important to understand

in term of biological aspects could lead this virus to be adapted to humans.

Let's start with influenza.

Influenza A are viruses characterized by the presence

of the surface of two glycol proteins, the hemagglutinin and neuraminidase.

The hemagglutinin we know in the nature approximately seventeen

different hemagglutinin.

And approximately ten different neuraminidines.

And we use these two liquid proteins to classify these viruses.

In humans we know only basically three

hemagglutinin that have managed together to humans and to infect humans.

And on the other sides in avian birds, or in wild birds, and also in pigs.

We can find a very high number of different and

migrating in and up to 17 and the ruminates.

So it just tells you that some viruses are not adaptable to humans and

could not cross the barrier of species.

And for the next few minutes I will stop on influenza and

also discuss a little bit of H1N1 2009.

And we won't have time to discuss about H5N1.

Concerning corona viruses,

corona viruses are part of viruses that are very, while adapted to humans.

Basically the first of the second cause of common cold, and

now the most frequent virus causing our respiratory tract infections.

Everyone has experienced infection with corona viruses.

Corona viruses as known by the names presented here,

and are really four different species that are adapted to humans.

These viruses like influenza have managed also to infect a very large number

of different animals.

And in animals they have emerged thousands of years ago and

then progress of the infected from type of animal, and

at the end, only four of them have managed to be adapted to human.

Again, an example of the importance of what we call the barrier of species.

So these two types of virus, influenza and corona viruses have similarities.

That cause sporadic outbreaks with a very high mortality.

They have a very large reservoir of different genotype.

And very importantly also they are transmitted by the airborne route,

which is the easiest way to cause an outbreak or

to be transmitted from one human to another.

Let's stop as I told you a little bit on the biological events

that could lead to human adaptation of these viruses and

let's stop on RNA which is the nucleic acid contents of these viruses.

And basically the genes that are part of

what will help these viruses to evolve toward human viruses.

When the virus replicate its genetic material, particularly antiviruses,

they use a viral enzyme that is quartered by the virus itself and

in the position to human cells, these enzymes are doing a lot of mistakes.

This leads to very frequent mutations.

And at the end of the day, after several cycles of replications,

you end up with verses that are previously very different of the verses

that was the first one in the different cycles of replication.

We have accumulation of mutations in what we call a progressive genetic drift.

Of course this genetic drift could also be associated with some

kinda pheno type that could lead to more variant strengths, or

strengths that are more adapted to humans, or more transmissible.

Another way to modify its genetic contents for corona viruses is to exchange genes.

There are several phenomenon that could help to exchange genes.

We will just focus on the one that is specific for influenza viruses.

Influenza viruses are made of different segmented genes,

when two viruses infect one cell, they can easily exchange genes.

This could lead to very important genetic change and what we call the genetic shift.

So in summary, influenza viruses and

in some way corona viruses also combine all the tricks.

They can accumulate mutations.

They can exchange genes and

have a very large animal reservoir that will favor the number of this exchange and

the number of mutations that are accumulate in this large reservoir.

Of course, this is not very important for humans but

this starts to be important only when these genetic change

leads to phenotypic change and then to several disease in humans

like it has been the case for these two viruses in 2013.

How long does it takes to these viruses to be adapted to human?

Let's just take one example which is the H1N1 in 2009.

In 2009, this virus emerge in humans and when we analyzed

the origin of the different genes that compose this viruses, we found that one

part of the genes come from a virus that has evolve in pigs for decades.

Another part of the genes is the, a mixture of different

genes coming from three different viruses that have combined in one pig and

then combined with the other part of the virus here in pink

to lead to this new H1N1 2009 virus.

But most interestingly, when we tried to

trace the origin of these genes we come back to the pandemic in 1918 and

we can trace the origin of most of these genes in 1918.

So in other words, the virus that caused the pandemic more than 100 years ago

has evolved in different animals and one day has combined to create this so

called that emerge again in humans.

And [INAUDIBLE] to small 100 years, which is very complicated to predict.

We have probably the same type of observations for influenza H7N9.

We can trace the origin of this virus in different birds, at least four

different types of birds, and this virus emerged probably in 2011 and 2012.

But we don't have a more precise history concerning the origin of this virus

since it's very difficult to trace the evolution of this virus in animals and

particularly in wild birds.

Is this H7N9 virus human adapted?

There are several arguments, biological arguments that suggest that the virus can

replicate easily in mammalian cells so it can be adapted to humans.

Genomes analysis reveals some mutations.

That's confer adaptations to human.

So this suggests freely that the virus could easily be humanized.

However on the other hand, when pigs are infected, they cannot transmit

the virus easily, and still the virus retains really a strong affinity for

the avian receptors that are found in wild birds.

But we really hear the article what we could call the yin and

the yang of the influenza virus, there in one part adapted to animals and

the other part could probably be adapted to humans also.

For the most corona viruses, we can trace that this virus

originated from a virus that we found in bats.

It's very close with viruses that have been identifies in bats.

It's not a virus that has evolved from a human virus.

So again, it's the same kinda story we have a new virus that emerge in human and

was identified in its regional reservoir here in particular bats.

We don't know at this time whether this virus could infect other animals

that are here in this picture.

This virus also emerged very recently based upon these

phylogeny diseases probably between 2009 and 2012.

The recent outbreaks that are still ongoing in

Saudi Arabia shown that seven mutations have already emerged and

that we already have some kinda genetic diversity and the virus is evolving.

So in conclusions the barrier of species is a real biological limitations for

many of these viruses, for any animal virus.

And virulence is really the optimal balance

transmissibility and pathogenicity.

If you can show that a virus is very dangerous or

a consider disease in animals.

It does not mean that it's dangerous in humans if it's not transmissible

at least at the large scale of a big house.

So transmissibility also is not easily achieved by any animal virus and

this is really the key to cause a pandemic.

RNA viruses have no brain and no strategy, but they have the ability to evolve,

thanks to high mutation rate, the ability to exchange genes like I showed you.

They have a very large animal reservoir that is called.

Day after day promote new strains.

The presence of different environmental and

complex environmental constraints have to be taken into account.

And what is very important that I tried to show you is the time frame

of these evolution is well beyond any human lifespan,

which really could complicate any productive prediction model

that can try to predict the evolution of these vessels and

of course will complicate any publican intervention.

And to illustrate this, we could have a look back in the 25 or

the last 30 years, and we can observe that even the most astute epidemiologists,

the best infectious disease specialists in biology has not

predicted West Nile Virus that has crossed over continents into the US.

The SARS outbreak in 2003, the Chickungunya more recently

that crossed the Pacific Ocean, the H1N1 of 2009.

We were expecting H5N1, and so

then we had the virus coming from the peaks in 2009.

And the most important year,

one of the most important pandemic of the 25 years, HIV.

It has also emerged from an animal reservoir across the burial of species and

caused this very dramatic outbreak in humans.

Thank you for your attention.

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Emerging Viruses in 2013: Influenza A H7N9 and Middle East Respiratory Syndrome-Coronavirus by Laurent Kaiser

全球健康：跨学科概述

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