People often consider the term ‘disease’ as referring to an illness which is acquired, such as pneumonia or a sexually-transmitted disease such as HIV , but in fact, any accepted medical condition with its own set of signs and symptoms can be classified as a disease. Moreover, while diseases are often the result of an attack of pathogens, they can also come about less aggressively as in the cases of alcoholism or depression.
When doctors diagnose disease, they need to be extra cautious as so many diseases share the same symptoms. According to pathologists (scientists who study diseases) at the Centers for Disease Control, a government organization based in Atlanta, Georgia, there are more than 13,000 known human diseases, spread across four general categories of risk and origin. An interesting fact: across the last 5,000 years, just two diseases have been completely eradicated – rinderpest, and smallpox.