Human societies have seen a significant decrease in mortality from infectious diseases over the past century. However, we must still struggle with ongoing pathologies we once thought were under control (cholera, tuberculosis, plague, etc.) as well as the new ones that have emerged over the last 30 years (HIV/AIDS, Ebola, dengue, West Nile virus, H1N1, etc). The vast scale of the global epidemics provoked by these viruses forces us to look more closely at the territories where they emerge.
In India, there has been an accelerated spread of dengue and chikungunya, both transmitted by the Aedes mosquito, which is particularly well adapted to urbanised areas. For example, the annual number of new dengue cases is estimated at more than 30 million, while the number of chikungunya cases is believed to have increased by 390% over the last three years. Recent estimates indicate that India is the country with the highest prevalence of these two diseases.
Cities, and disease, on the rise
The rise of these infectious diseases is often described in terms of biological processes, but they cannot be reduced to just this dimension. A range of factors play a role, in particular increasing urbanisation and human mobility. The trains connecting Mumbai to its periphery move more than seven million travellers a day, and New Delhi’s metro system caters to 2.5 million daily commuters.
The growing attention paid to the epidemiology of these viruses can hence be clearly seen as a direct result of the urban transition taking place in India over the last 30 years.