In the 15th century, modern shipbuilding and seamanship began to develop gradually. Most countries in the world started to explore the world, not only trading for good, but also for trading slaves, which created connections with other countries. This activity caused several diseases, like smallpox, measles, and bubonic plague, to spread easily in tropical environments in Asia and North America. There are several diseases that still exist today, even more and more types appeared, like Ebola. Moreover, modern transportation transmits those illnesses faster. When people discover a new, highly infectious disease, often times, it has already been spread, through one of the five major modes of disease transmission: airborne, waterborne, blood borne,
