 So I'm Elaine Denise, I'm a researcher at CIRAD, I'm a veterinarian and disease ecologist. So I'm based in Zimbabwe and today I'm here to talk about the health of the environment and the link with infectious diseases. So given my background I will talk about animal and human diseases but some of the concepts are also applicable to plant diseases. So and just first an important aspect to note is that as you know infectious diseases are driven by environmental and ecological drivers but also by sociological and economical drivers. So I will only give you part of the picture here but what I really want to show basically is that the environment and the health of the environment is really a central part of the issue of infectious diseases and that environmental actors really can play a key role in disease prevention and management. And the idea here of this workshop is also as Alex introduced before that the environment is often quite neglected while it should be the opposite, it is very, very central. So let me start from the beginning just like a healthy environment, maybe I should have put ecosystem can be reflected through a stable climate, high biodiversity, persistent vegetation, habitat connectivity and so forth. And human cost pressures like intensive agriculture, mining, industrialization, wood industry can actually lead to what we can call an unhealthy environment with accelerated climate change, biodiversity loss and also habitat degradation, forest fragmentation and so forth. And these can in turn impact infectious disease dynamics through complex mechanisms. This is not an exhaustive list, it's just so that I can give you some examples of these mechanisms for a better understanding. And I chose, I selected examples that are based on well studied systems so they don't necessarily occur on this continent but they can definitely be applied also. So if we look at the habitat loss, the effect of the habitat loss on infectious disease transmission, I take the example of handra virus in Australia. Handra viruses, I don't know what happened here but anyway I also have a little problem but it's okay. So they are basically maintained and transmitted by bats flying foxes. So basically the bats, when they roost in these nice trees, they shed the virus in their urine and they excrement and horses can get contaminated while grazing contaminated grass. And these horses can get very sick and they often die from this disease through respiratory and neurological disorders. And in the meantime, these horses can transmit the disease to people. So and I selected this example because a team in Australia led a very long term study and analyzed over 25 years of data and when you look at environmental drivers, it's really important to look over the long term, otherwise you won't detect anything and it's also good to have a large spatial scale to detect, to be able to understand underlying mechanisms. And so basically these bats, they normally forage in forests, especially over the winter. They are winter flooring trees so they really rely on that and what they see is that there's a lot of land use change and forest clearance for urbanization and agricultural purposes. And so these bats go through periods of food shortage and when there's food shortage, what they do is that they start roosting in smaller colonies, they form smaller groups in urban and agricultural areas. And what the researchers noticed is that after food shortages and in these new colonies, the viral shedding in the droppings actually increase because these factors bring like cumulative stress so the immune system might be affected and this in turn impacts the dynamics of the viruses, viral circulation. And on top of that, in these new winter roosts, there's also a changing interface. So there's closer interface with domestic animals, with horses, more outbreaks in horses and hence an increased spillover risk also in humans. And climate change on top of that causes also more food shortages. So it's quite complex but at the end what it shows is that habitat change can impact the behavior of the animal host, the abundance, the distribution of the animal hosts and also its physiology, the immune system and also the interaction with other species including humans. And on the African continent, for instance, Hendra-like viruses have been discovered in bats. We don't know the impact for human health yet. And also very similar dynamics are suspected for Ebola virus. So Ebola virus, I put it also as an example but it's not such a good example because the ecology of Ebola viruses remains very blurry. So we suspect bats to play a role in the transmission, the maintenance of the transmission with possible direct transmission to people or through what we call a bridge hosts like other species of animals like darkers and primates which can be infected and in turn infect people. And so a study that looked at the distribution of outbreaks shows that outbreaks are more likely to start in highly disturbed forested areas. So on this map on top it's like a map of the forest in Central and West Africa in 2000 and then below it's 14 years later. In orange you see the degraded parts of the forest and the yellow triangles are the outbreaks. And basically what they show is that these outbreaks occur where there is forest. So there is the reservoir host, there is also, of course, increasing amount of people but mainly there's increasing forest fragmentation. So there's ongoing disturbance. And so this disturbance can affect once more the behavior of the bats, even the distribution. Some fruit bats might adapt quite well to these new transformed habitats. And actually we have a student, a PhD student who colored with GPS colors some hammerheaded fruit bats who are suspected to play a role in Ebola virus transmission. And so what she showed, well what she found was that these bats actually prefer to forage in agricultural lands which are those in orange around the purple villages compared to the forest. So all the black dots are the foraging sites and they tracks in gray but they definitely spend more time in the agricultural lands. So this is just to show that these habitat transformation do impact or can impact disease dynamics. So if we look at biodiversity, as you know we've spoken about it already in different speeches, it's very important for food and water security, for nutrition, sustainable development and so forth. It is really, really, really important to preserve our biodiversity because of all that. But when it comes also to pathogens, the link between biodiversity and pathogens is very, very complex. So for various reasons, we can't speak about everything here but mainly if you look at the global scale what happens. So we see that the pathogen richness, so the number of different pathogen species in a broad area increases with the number of bird and mammal species. So this can be explained in different ways but in any case that also means that when there is more diversity, more species around, there's more pathogen species and there's the likelihood of a pathogen to be able to jump to another species or like humans is of course increasing. So then we can consider these areas with higher biodiversity as hotspots for infectious disease emergence. But what happens at a local scale? So things might look very different when you look at a smaller scale. There are different mechanisms at a smaller scale which can explain a different ways the infectious disease is respond to biodiversity and one of them is the dilution effect. So the dilution effect says that a higher biodiversity protects us against infectious disease risks. So basically when we lose biodiversity, the prevalence and the transmission of pathogens increases. It's a very controversial mechanism because it's very complex and it only occurs in very specific host pathogen systems. So bear that in mind, it doesn't happen everywhere, it's not the general rule at all, it's just to give you an example of these interactions. And so I will explain it to you through a natural dilution effect that was shown in hantaviruses in small mammals. So hantaviruses are zoonotic viruses that are transmitted by rodents and they are quite widely distributed. They exist in America, in Europe and also some hantaviruses have been discovered in African countries like in Guinea, in small rodents with an impact on human health too. And a higher diversity of hantaviruses is constantly being discovered in other animals like shrews and bats. This example is in Sweden where it causes hemorrhagic fever syndrome in humans. And basically it's transmitted by these small rodents called bank voles. And these bank voles, when you have a situation with a low diversity of these small mammals and where these bank voles are quite abundant, they are good competent hosts, they are able to maintain and transmit the virus and they do a lot of movements, there's a lot of encounters between animals and people and so there's a lot of transmission. But what happens if we introduce like the smaller animal, the common shrew? The common shrew is not a competent host, it is not able to maintain or transmit the disease. But it's a competitor to the bank vol and a predator on the bank vol. And basically the effect is that it will affect behavior of the bank voles who are going to change their movement patterns and there will be less encounters and less aggressive encounters between bank voles and hence less transmission, which we call encounter reduction. On top of that, if we add another one, which is the field vol, which is a direct competitor of the bank vol, this one will also change the movement and the behavior and on top of that will reduce the density of the bank vol population because they compete directly for resources. And there we have a reduction of the susceptible host population, hence less transmissions. So this is an example of how this can function. Climate change, again it comes, we've been talking about it quite a bit too, climate change can have an impact on diseases through different ways, so it can basically affect directly immunity and physiology, not only of the hosts, but also of the pathogen. So I invite you to read, I've put some bibliography at the end, some papers which explain that. Of course climate change has an impact on habitats, on biodiversity, et cetera, which in turn impact infectious diseases. On water systems, we've been talking about cholera, cholera has been shown to be quite sensitive also, a sensitive disease to climate change. And I want to give you the example of vector born diseases, which are clearly impacted by climate change because vector born diseases are transmitted by all these little bugs like mosquitoes, flies, ticks, which are very sensitive to rainfall and to temperature. So this is an example of malaria, endemic in many areas, transmitted by mosquitoes and the mosquito as well as the parasite are sensitive to the rain, they need a certain amount of rainfall and a certain level of temperature to be able to breed, but also for the virus to replicate, for the parasite, sorry. And models show that there's an increasing risk in tropical highland regions, particularly East African highlands, which are not suitable for malaria yet, but will become perhaps suitable. Typically also in Harari, we don't have malaria, but hopefully it never happens, but it's one of the worries and one of the risks. You have the example of arboviruses, dengue, zika, et cetera, transmitted also by mosquitoes. The example of dengue virus, dengue virus. So it's a disease that touches millions of people. It's very wildly distributed. It's transmitted by mosquitoes and many transmitted in urban settings. And the impact, the burden has been increasing a lot over the past years. And basically also models based on climate change show that the population at risk will keep increasing drastically over time. And for instance, even in France, we now have a local transmission of dengue fever that already occurred. So it's, and then we have the example of tick-borne diseases. These tick-borne diseases, we have examples of endemic diseases that affect livestock, for instance, like telleriosis. Telleriosis is transmitted by a tick called ripicephalus appendiculatus, which is also its distribution is predicted to also change with climate change and different climatic conditions. And this will, of course, also impact the areas that are suitable or non-suitable for telleria transmissions. This is in the little squares there. And it's important to note that some areas will become suitable and some areas which were suitable will become unsuitable for transmission. So it can go in both ways because it is complex. So it's not only negative. Sometimes it can be sort of positive, I suppose. So all this to basically show that the unhealthy environment is also really a starting point. It's not the only one, but it can really drive epidemics, pandemics, mortality, morbidity, and so forth. So if we want to prevent that, we really, so we as an animal disease expert, as a human disease expert, we can, of course, do some sort of prevention. We do surveillance. We can do control. But we really need to work hand in hand with actors from the environment. So be it at ministries, academia, NGOs, private sector, and also civil society, if we really want to do better prevention. And like Alex pointed out earlier on, it's not just about prevention, but it's also about evaluating the impact of our actions. It goes in both ways. It's complex. We have an action. It will affect infectious diseases somehow. And we need to be able to understand this and work together. So just one thing that I want to point out, when we talk about infectious diseases, many people always think zoonosis, emerging, reemerging zoonosis. Please bear in mind all the endemic diseases, even non-zoonotic diseases. We were talking about malaria or so, which originates from animals long time ago, but not anymore. These diseases are as important. They have huge impacts, so they should really not be neglected as they often are. And the second point is, don't forget that all these factors also impact non-communicable diseases. As we saw in earlier presentations, well, yesterday, these non-communicable diseases are extremely important in some areas even more important than infectious diseases. So I'm just, so I'm talking about this because it's my expertise. But it's not central. There's a lot more to it, so just keep that in mind. Thank you very much. Some papers to read if you want.