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Tropical forests have the greatest biodiversity in macroorganisms on the planet, and they are also the richest in myriads of microorganisms for which so little is known today. Over the last 50 years, many of these microbial forms, that are naturally embedded into wildlife or the environment, e.g. soil, water, have revealed to be more or less dangerous pathogens for people exposed to these new natural threats, i.e. emerging infectious diseases. Here, we discuss about the extraordinary diversity of microorganisms that are present in tropical rainforests. We first present the main global distribution patterns for microbial forms at the interface between tropical wildlife and human, and second we provide an epidemiological picture on how microbial transmission from wild animals or the environment to people operates in tropical areas through four case-studies. We examine the animal hosts or environment, and transmission mechanisms involved in spillover of zoonotic or environmentally-persistent microbes, and identify land-use changes through deforestation for the development of agriculture, and contacts with wildlife notably through bush meat hunting as major drivers that facilitate mixing of diverse animal hosts and their microbial communities with human during practices. With an increase of deforestation in the tropics and more contacts between wildlife and people, new emerging disease events with high epidemic and pandemic potential will happen, that should guide new health policies and strategies at the global scale.