Vers une société résiliente au changement climatique / Building a Climate Resilient Society : colloque organisé dans le cadre de l’initiative « Avenir Commun Durable »
Conférence du 25 janvier 2024 : Urban Epidemic Risk at the Time of Anthropocene and Climate Change
Session 3: Climate Change and Health
Intervenant :
Philippe Sansonetti, Professeur du Collège de France
As the world’s population grows, so does the rate of urbanisation.
The megacities that are emerging (20 cities with more than 15 million inhabitants, half of them in the south) combine numerous vulnerabilities to the risk of epidemics (or infectious diseases in general). These vulnerabilities are set to increase under the impact of climate change, particularly global warming, conditions which generally favour microbial growth and proliferation.
Lire la suite : https://www.college-de-france.fr/fr/agenda/grand-evenement/vers-une-societe-resiliente-au-changement-climatique-building-climate-resilient-society/urban-epidemic-risk-at-the-time-of-anthropocene-and-climate-change
En savoir plus sur l’initiative « Avenir Commun Durable » :
https://www.college-de-france.fr/avenir-commun-durable
Retrouvez les enregistrements audios et vidéos du colloque et son texte de présentation :
https://www.college-de-france.fr/fr/agenda/grand-evenement/vers-une-societe-resiliente-au-changement-climatique-building-climate-resilient-society
L’initiative Avenir Commun Durable, dans laquelle s’inscrit ce grand événement, bénéficie du soutien de la Fondation du Collège de France, de ses grands mécènes la Fondation Covéa et TotalEnergies et de ses mécènes Faurecia et Saint-Gobain.
Consultez la charte du mécénat de la Fondation du Collège de France :
https://www.fondation-cdf.fr/wp-content/uploads/2023/08/Charte-ethique-Fondation-du-College-de-France.pdf
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Okay so the idea here was to focus on on Urban environments because I cannot cover everything about microbes everywhere on the planet and and and sort of Identify some vulnerabilities of our Metropol with regard to our interface with with microbes and we’ve already heard a lot about microbes in
The first and the and the second talk in this session the idea is to sort of project ourself possibly in the future and consider how climate change of course global warming part of this climate change but also human behaviors everything that is part of this anthropocene concept I mean changes in
Diet medication and so on and so forth how is this going to affect in a very specific environment which is the urban environment uh our health at the end of the day that is the question here so I don’t want to go back too much onto some
New numbers and and and and figures and you’ve heard already from Chris uh it it’s it’s obvious that at least I’m not too corporatist about it believe me but still I think that in The Narrative of modern ecology I mean microbes are a bit forgotten in in a way and I’m glad that
Ocean microbiome has been put up on the stage now so I mean in a way of course uh the macroscopic life world is is is huge I mean it’s it’s 85% of the planet biomass and it’s essentially dominated by plants like I’ve put that in gigaton which I think is interesting there are
40 470 gigaton of plants on the on the planet and and only two gigaton of of human uh and animal flesh I would say on the other hand microbes of course are are behind it it’s only 16% of the biomass but it’s 95% in terms of
Biodiversity so I mean and and we all know of course that microbes are important in terms of their role in the big cycles of life the planet this has already been mentioned microbes are very important as symbiotic microorganisms to the plants for instance there will be no good
Agriculture without the microbes in the rizosphere they are good at depolluting soil and and ocean they are also symbiotic to animals and humans of course and this is all about the issue of the microbiome we used to see the human microbiome as a sort of sensor uh
In greator and an effector of the environment and it’s in a way a possibility for us as humans or or animals in general physiology to to be able to possibly react more rapidly to some environmental changes because the microbes themselves have this capacity to evolve Faster by their capacity to to
Mutate or their capacity to uh to be to undergo some transfer some lateral transfer of genes from other microorganisms so all all this is kind of a very fascinating symbiotic symbiosis and I hope we will have a chance to come back to this not forgetting to say that again we are
Living in the same environment uh we are sharing the same environment humans animals microbes plants and this is all of course about this new or not so New Concept of one word one Health uh which sort of considers under different angle these very fascinating aspects of of
Interactions uh so I mean if we now look at the urban situation uh it’s clear that uh the uh City the big metropoles they sort of aggregate all the risk factors with regard to alteration of microbial ecosystems and their impact on on human health uh the issue of course
Is a growing issue because as the world population increases uh 8 billion last October uh the uh urbanization rate also increases and increases quite fast it’s largely now over 50% and it’s anticipated to be about 75% probably by 2050 and and and this is really making the urban environment as an per se
Concept that we we need to try to to to explore in this in this context so what are the uh vulnerabilities of of of the big cities knowing that at the moment on the planet there are 20 metropoles that have more than 15 million inhabitants
And half of them are in Middle to lwi income countries which means that the threat of course is even higher for these Metropolis so of course there is a an issue of public healthiness uh an issue of clean water an issue of safe food that is very important to be
Considered and that’s going to be a Target possibly for microbes to alter under this climate change and other changes in Behavior Uh cities of course are uh really places for possibly epidemic development and this has been addressed by Professor Hayes uh there’s many reasons for this uh of course the
Density of the population especially for air transmitted microorganisms uh public transportation Gathering cultural um Sports Gathering we’ve seen that during the covid 19 period there is also the issue of poverty which is a major driver for you know changes in in in ecosystems uh microbial ecosystems and and risk for
Infection and the complications of these infections I mean you can list all these vulnerabilities of the Cities not even speaking about the fact that these big metropoles are often home for big uh air transportation hubs and we know the role that these places have in the transmission of epidemics to the world
Planet one thing that has been addressed already is the what we call the enological risk which is the the development of vectors in urban uh situation in urban context and this is clearly a situation that we are facing at the moment in France with idad buus
Which in a matter of 20 years has basically from south to North colonized the entire country taking advantage of its better adaptation to our conditions eggs are very robust but also Transportation I mean clearly railroads and and and and and routes have been important in this colonization and we
Are starting to see now secondary or tertiary cases of dang for instance in the south of France in the area of neim for instance saying that maybe in the near future we’re going to have dangi becoming epidemic and possibly emic again on the long term as it was at the
Beginning of the 20th century so this is really a threat and and this shows in a way that we haven’t probably addressed enough this risk like by education of the population I don’t have time to get into this uh I mean all and and our cities are not really ready to cope with
Uh this situation with these new uh vectorial Cycles uh there are some wh projection say that uh in in the the field of you know Public Health I mean there will be probably by 5 to 10 years an increase of about 10 20% of food and and and water born
Infections okay so I think there is one issue that is very important when you give the sort of global pictures is is there a way to sort of acquire it’s been done with tan a sort of global picture of the of the urban microbiome it’s you
Know it’s bit of a provocative term but it’s something that is currently developed by the help of you know Big Data uh New Generation sequencing and bioinformatics of course give you Fantastic Tools to study uh some Urban ecosystems question is very often these ecosystems present a very low biomass of
Microorganisms like air for instance or like Handles in the subway I mean these are sites where you know you would like to know exactly what’s going on at one particular time but this opened the way to contaminations of these samples and and so this is a very subtle and and
Delicate approach that has to be conducted with a lot of controls but still this is on the way it has been developed for instance in Singapore in housing systems uh to detect new emerging microbes in the environment of these places and like Asus or or other of these microorganisms are now
Detecting using this kind of of approach that’s the the the work of stepan Schuster for instance but there are some different angle under which these new technologies are now used to identify or Define some of these Urban microbiome aspects and uh for instance there has
Been a paper a few couple of years ago dealing with 60 different cities on the planet and and during this approach in some hotpots I was talking about you know Handles in the in in the subway I mean these kind of places where lots of people meets on on on an everyday basis
But other hotpots of course exist that you can imagine and and each of the city has some sort of different signatures that are marked of their you know identity in a way depending upon you know many factors that you can imagine you can also follow the there there are
Lots of new species that are detected lot of new viruses that are circulating for which we had no idea before again it’s a bit the world of Silence that is revealed at this scale by these approaches and this is of course the beginning of a proactive way of of
Surveying surveillance of this of this Urban ecos systems in in the future of course there are uh you know approaches that look at uh the uh impact of high temperature this was done in China for instance showing before and after a canicule that the air composition in
Terms of micro had change with a switch toward firmicutes which are Grand positive anerobic microorganisms very much porating microorganisms how much of this may have impact on health it’s not known yet but it’s on the way and we have to continue these studies Nairobi Kenya they’ve done studies on hotspots
Where humans domestic animals and and and wild birds meet in some you know areas of the city 90 or 99 places different hotpots in the cities and they have shown very well that there were a permanent exchange of microorganisms between these three different population and that these exchanges especially from
Wild birds were kind of structuring these microbial populations so this is very important for instance to sort of anticipate on the occurrence and development of possible zootic infection and these tools are increasingly of course used I would also like to mention some new approaches this new few years
Ago now but it’s been crystallized during the co covid-19 period Obin in France but in different other countries in Europe and in other places in the world which look at the composition of the West Water um before the purification stations and and this is a way giving you an angle on on
The again on this Urban microbiome because all this FAL material that we are basically sorry before the lunch but defecating in the in in in in these West water pipes is is basically a reflection of us of our m mobes virus bacteria but also now of our drugs the the medication
That we use it it allows to look at the antibiotic consumption for instance on on psychotrop consumptions hormone consumption and and this is much more sensitive in a way than just looking at the pharmacist registers and and and trying to see how much of these medications have been sold so there is
Kind of Revolution here which has I think is important to to measure what this could be so to sort of cover some some one of this vulnerability it’s obviously water and I will go fast on this but this is very important issue it’s clear that we need
Clear water but the increase in the world population the restriction on water availability uh the increased and legitimate demand for good drinking water for instance as well as the changes in climatic conditions is going to be like an explosive cocktail with regard to availability of safe and and
And and and high quality water in in in big cities in big metropoles in our Metropolis in industrialized country uh the purification of water is based on on your good Technologies sedimentation uh the microb filtering the uh isue ALS of reverse osmosis all this is is is is carried out and at the
End of this pipeline after the purification usually the the microbial you know is is all several order of magnitudes and and below and and sometimes zero Colony forming units so the water is bacteriologically absolutely pure but this is unfortunately not shared by more than half of the world populations in these
Metropoles where the standards of quality are not the same but it’s not just to clean up this waste water it’s also to you know ensure that the distribution is not you know again contaminating and it’s clear that there are bacterial ecosystems in the water distribution system this huge network of
Pipes flavobacteria for instance is a kind of proteobacteria that is dominant in this system and it’s clear that even if these microbes are not pathogenic they might be pathogenic for imuno compromis people so this is a very sensitive marker that has to be surveyed and and clearly one big issue that
Emerged from all this is biofilms and biofilms is is a very important uh element which shows that microbes in any ecosystem uh live in communities it might be single communities or it might be multi- specious communities and and and this is very essential because it’s a way for the bacteria to
Survive basically in the environment in many many places uh initial there are there are pioneers microbes that start to adhere to a surface whatever it is a biotic on abiotic surface and then they start growing and they develop regulatory mechanisms which allow them both to reduce their metabolic activity
And survive as well as to produce massive amounts of of polysaccharides of proteins releasing DNA and all this forms this kind of you know protective layer that allows them to survive in the environment whatever uh you know aggression they could undergo can be antibiotics for instance they are resistant to
Antibiotic in this in these systems but it can be also chlorination for instance that is used uh in uh the uh cleaning of of of water so it it is clear that this is going to be an issue so let’s look at two examples one which is the the how
The the the the waste water is conducted to the purification station it goes through these big you know pipes that are made of concrete and and it’s clear that microorganisms are not good for concrete they tend to colonize the the surface and and and The Matrix and what
They do is because they are essentially anerobic microbes they they acidify and we heard acidification about ocean uh it’s not good for ocean it’s not good for pipes what it does is to induce cracking and and and and and the crumbling of of of the concrete Matrix
And and this leads to a destruction and it’s clear that these microbial population these biofilms in experimental models they increase in size size they increase in microbial density they change their microbial density according to increases in temperature so this is going to be one of the vulnerabilities and one of the
Major microorganism family is tus they are anerobic uh they they produce uh by fermentation there are nutrients of course in these West Waters uh they they produce acetate they produce lactate they produce berate these are organic acid but they also produce anorganic acid uh the these microbes are are
Involved in the sulfur cycle so they they basically uh they they basically um o oxidize the sulfur and and and and they reduce the sulfat and and all this leads to production of acids like sulfuric acid which is very aggressive for for concrete in fact the the the the major
Protective element in terms of chemistry of concrete is the pH it’s very high pH 11 and within hours of development of these biofilms you might see that the pH goes down towards sometimes ph3 which is pretty acidic and and and destructive again for for the for the concrete
Matrix so all this is is an issue that has to be taken into account of course we we see similar situations uh in the distrib bution system where this flavo bacteria also have this capacity to decrease the ph and this interestingly is is of course altering the qu the
Quality of water because the the microbial composition increases it also increases in diversity uh there are some ecological succession that are induced by this uh chemical elements and and and basically the when you look especially using this uh Big Data analyz this you see that it’s not just this L bacteria
It’s a lot of new microorganisms that were present in the sample at very low density which are now uh developing and this also includes uh you know the fungi and and and and moles and and and so on and so forth so it’s there is a whole
Ecology of this that has to be studied because it is essential if we wish for instance to keep water quality and to keep uh these uh de the distribution system from from corrosion uh one big issue again is biofilm uh the way we we clean up this distribution system we
Would say is very archaic what we do is Flushing and and and and and also you know chlorination but these biops make microbes resistant to chlorination so there is nearly really a need for good science here uh for Innovation uh in terms of of treating uh these elements I
Would just like to finish up on two slides and and make it very short I’ve been talking about uh the climate changes and and global warming in term for instance of facilitating bofilm developments and corrosion uh of water distrib collection or Distribution Systems but we’re also living in a world
Where we are ourself by our Behavior altering microbial composition of of these ecosystems and this is the crisis of antibiotic resistance uh the situation created by anthropocene is that we are exaggerating in using you know my antibiotics in in the medical and Veterinary environment of course but
A lot have been done here to educate the doctors but still more than 50% of the antibiotics that are used in the world are not used for medical or veterin purpose they are using for um for cattle breeding uh for two reasons why for sort of prevention of infections and the
Other one is but because there are good growth factors and this goes also for Fisheries for instance where tons of antibiotics are released in waters every year in many places of of the world fortunately it’s prohibited in in the European Union but basically we think that about 300,000 tons of antibiotics
Are released intact on the planet uh in many many different places but Urban sites of course are very essential as providers of these antibiotics as well as the breeding intensive breeding facilities in some places of the world so this causes the antibiotic resistance crisis because these low concentration
Of antibiotics that we can even find in the river now uh they maintain selective pressure on What’s called the resistor of these microorganisms in the environment that facilitates the survival of those that are resistant to antibiotics especially to threo and to Fons for instance which are not necessarily well degraded because they
Are chemical elements they are not produced by plants or or by microorganisms themselves and so my last Point je Marie I apologize is that uh I mean maybe this antibiotic resistance crisis which is clearly linked to human behavior has hidden another crisis which is the crisis of microbial
Biodiversity and it seems that this crisis of microbi diversity in in association with with humans is something that now needs to be really put on the on on on the table uh for the reason that I say because our microbiome which is sensitive to these antibiotics and and
Other stressors uh that you can think of in the environment that the anthropo has created our microbiome are suffering from this and it’s sort of developing what we now call A disbiosis A change in microbial composition a change in microbial diversity which tends to reduce this Lees space for what we call
Pathion which play a role and we can see a lot of now correlation but also experimental proof of demonstration that this this biotic situation that this created by the anthropos scene is probably the cause of this uh famous now epidemic non-communicable postmodern diseases like allergy atopy obesity diabetes cancer colon cancer for
Instance not necessarily the essential cause but at least factors that facilitate the development of these pathological status so we really need to take all these elements into account because again this all changes that is prepared by you know the aggravation of human behaviors with regard to bad eating habits and all this is
Concentrated is cities for instance uh of course pollution and other elements are impacting a lot on on this microbiome and this is really a new science that is emerging which is important to consider so I will stop here sorry about the some minutes that I took that I didn’t deserve uh uh thank
You very [Applause] Much