Scientific evidence validating spiritual beliefs for controlling pathogenic microbes in the Ganga river

During the Kumbh, the Ganga at the Sangam in Prayagraj, where it meets the Yamuna, showed greater microbial diversity than either river before their confluence. Mass bathing altered the density and diversity of archaea, bacteria, phages and viruses, while fungi, protozoans, cyanobacteria, green algae and diatoms remained largely unaffected. Notably, this study was the first to report archaeal phages, cyanophages and mycophages in the river system. Archaea species richness was higher in the Yamuna (127 spp. during Pre Kumbh), whereas bacterial diversity was greater in the Ganga (2764 spp.). The Ganga exhibited a higher relative abundance of skin, oral and gut archaea and bacteria, except for gut bacteria, which were more prevalent in the Yamuna. Skin and gut archaea showed strong positive correlations with the number of devotees (r = 0.818 and r = 0.870, respectively), while oral archaea were less affected. Pathogenic microbes with high fatality rates were more common in the Yamuna. Variations in archaeal, bacterial, phage and viral communities were influenced by physico-chemical parameters, ion levels, nutrient content and devotee's load. The Ganga exhibited higher phage diversity and a greater phage-to-bacteria ratio than the Yamuna. Hence, phages regulate the pathogenic bacteria through predator-prey dynamics, consequently reducing infection risks. Despite mass bathing by over 100 million devotees, which sharply increased nutrient and pollution levels, no endemic or epidemic outbreaks were reported.