Natural causes of death refer to internal factors that cause the body to shut down, such as diseases or internal malfunctions. Some examples of natural causes of death include heart disease, cancer, stroke, pneumonia, and HIV/AIDS. These causes of death are not directly caused by external forces, other than infectious diseases. Natural deaths are the most common type of death globally and in the United States. Medical doctors classify deaths into five different manners of death: natural, accident, suicide, homicide, or unknown. The specific cause of death plus the circumstances surrounding the death influence the designation. Determining a natural versus an accidental death can sometimes be challenging. For example, someone who used illicit drugs for much of their life may die of natural causes related to that lifestyle choice.