A study published on May 20 in the journal Cell Reports reveals that even minimal exposure to modern medicine can rapidly alter the human microbiome. Researchers, led by Maria G. Dominguez-Bello from Rutgers University, examined Indigenous communities in the Amazon rainforest who had limited prior exposure to medical care. Following the introduction of a World Health Organization-supported program for treating river blindness, the gut microbiota of these communities began to resemble that of urban populations after just a few medical visits. Over a four-month period, the diversity of gut microbes declined, with significant reductions in bacteria linked to fiber digestion, such as Prevotella and Treponema. Conversely, bacteria more common in industrialized societies, like Bacteroidota and Verrucomicrobia, increased. The study also found shifts in microbial communities in the mouth, nose, and skin, with children showing the most pronounced changes. Dominguez-Bello emphasizes that while medical interventions are crucial for health, strategies to protect gut microbiome diversity should be integrated into public health initiatives to mitigate potential risks associated with these changes.