Today approximately 70% of all diseases that affect humans are the result of zoonotic spillover. Zoonotic diseases are those that originated in a different species, and through contact with humans have mutated so that they can infect humans. Modern examples include the Zika and Ebola viruses, both of which originated in nature but did not infect humans. Deforestation and climate change have led to many encounters with disease causing agents that lead to spill over. Climate change is affecting the ranges that species inhabit. For example Zika carrying mosquitos are migrating farther north into North America, outside of their historical ranges. Deforestation causes species that historically inhabit jungles or forests to venture into towns and cities which brings them into contact with humans. Diseases that have historically only existed in remote parts of nature are now being exposed to heavily populated and connected villages, towns, and cities. Globalization allows these diseases to spread more rapidly and infect a larger amount of people. Battling diseases that traditionally would kill 90% of a village and then fail to spread anymore in a globalized world poses a serious challenge to health agencies around the globe. Today, early detection, and exhaustive efforts by healthcare workers to prevent the spread of infectious disease is becoming the most important factor in the fight against the next global pandemic.