Symptoms are the feelings or changes experienced by an organism when it is ill. These may be caused by a pathogen, the environment, lifestyle, or a mixture of these.
Diseases can be grouped into two types:
communicable, which are caused by pathogens and can be transferred from one person to another, or from one organism to another – in humans these include measles, food poisoning and malaria
non-communicable, which are not transferred between people or other organisms
Non-communicable diseases include:
cancer
diabetes
genetic diseases and conditions
heart disease, which is also called cardiovascular disease neurological disorders
Other factors that can have major effects on physical and mental health include:
diet
lifestyle factors such as the use of alcohol and other drugs
stress
situations that may occur in a person’s life