Where did Disease originate?

Disease has likely existed since the very first life forms evolved on Earth. Microorganisms such as bacteria and viruses are thought to have originated from early pre-cellular life forms, and as life evolved, so did these microorganisms, leading to the emergence of various diseases. As life diverged into different species and colonized new habitats, so too did the diseases they carried. Some of the earliest evidence of disease in humans dates back to around 3000 BC, when Egyptian texts described symptoms and treatments for various illnesses.