Résumé
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.
Factors favouring urban epidemic risks are: (1) Deterioration in water and food hygiene. (2) Urban air pollution. (3) Movement towards urban areas of mosquito vectors establishing vectorial systems allowing the introduction or return of pathologies linked to this entomological risk, such as dengue fever. These entomological factors are particularly influenced by climate change. (4) Population density facilitating human-to-human transmission, accentuated by large gatherings (cultural, sporting, etc.). (5) Urban and peri-urban poverty, a major vulnerability that climate change will exacerbate. (6) Finally, large cities are also major air transport hubs, facilitating the spread of the pandemic.
Given the limited time available, the water risk will be taken as an example of the impact of climate change, in particular global warming, on water quality, both in terms of wastewater treatment and distribution. The formation and development of biofilms, which are highly sensitive to global warming, will be developed in particular.
Finally, major cities are also at risk from the human behaviour that characterises the Anthropocene. One example is the immoderate and often unjustified use of antibiotics, which is causing a pandemic of antibiotic resistance due to the dissemination of antibiotics in the environment. It also seems to be leading to a reduction in the richness and diversity of microbial ecosystems, and in particular human microbiota, which is linked to the emergence of so-called "epidemic, post-modern, non-communicable" diseases whose incidence is increasing at a worrying rate, such as allergy/atopy, autoimmune diseases, chronic inflammatory bowel diseases and colorectal cancer.
