A disease is chronic (as opposed to acute) when it is either persistent or long lasting - generally for a period of at least three months. It does not have to be terminal, but many chronic diseases such as cancer and AIDS are terminal.
A disease is not described as chronic when it is long lasting but has lengthy periods of remission or latency. As such, herpes, although incurable, is not chronic, but instead has numerous acute phases.
Most chronic diseases are not contagious, but there are exceptions such as AIDS.
Chronic diseases result in more deaths from disease than acute diseases. However, this includes diseases such as heart disease which, for the most part, do not interfere with daily activities and are often relatively asymptomatic. About half of all Americans have at least one chronic condition, and the odds of having a chronic condition rise to over 90% for those over the age of 65.
The majority of chronic diseases are the result of lifestyle and diet, with most of the rest being due to other metabolic risk factors. In addition, social and economic conditions also put a person at risk for chronic conditions. However, many chronic conditions are not due to these factors and include Alzheimer's disease, Parkinson's disease and arthritis.