Health can be defined as a person's physical, mental and social condition.
Good health is more than being free from disease; it is having a positive outlook on life and feeling good physically. To enjoy good health, a person needs proper shelter, nutrition, exercise, sleep and rest. Good hygiene and the access to medical and social care are also important.
Epidemiology is the study of patterns of diseases and the factors affecting its spread. Incidence, prevalence and mortality for a disease may be determined. Collecting information on the distribution of disease helps to identify the underlying causes and if it turns out to be infectious, may point to how it is transmitted.
Disease is a disorder or malfunction of the mind or body, which destroys good health.
Disease may have a single cause - for example, malaria or be multifactorial, such as heart disease. Diseases have characteristic symptoms, which may be physical, mental or both. Those that have a sudden onset with rapid changes, but only last for a short time are called acute, while the effects of chronic disease may continue for months or years.
An infectious disease, which is always present in a population, is called endemic.
An epidemic occurs when a disease suddenly spreads rapidly and affects many people. If a disease spreads over a continent or even the world it will be termed pandemic.
Categories of Disease
There are nine main categories of disease but some diseases are more difficult to classify and fit into more than one of them.
- Physical Disease
- Infectious disease
- Non-infectious diseases
- Deficiency diseases
- Inherited diseases
- Degenerative diseases
- Mental disorders
- Social diseases
- Self-inflicted diseases
Categories of Disease 2
Physical disease - These diseases involve temporary or permanent damage to the body and include all the other categories except mental disease where there is no sign of physical damage to the brain. An example would be leprosy.
Infectious disease - Pathogens are organisms living in or on our bodies, causing disease. Infectious diseases are caused by pathogens such as viruses, bacteria, fungi, protoctists, worms and insects, which can be transmitted from person to person. This may be via normal social contact - for example, chicken pox, or via food and water, sexual contact or an animal bite. Carriers are people who can transmit the pathogen but do not have the disease symptoms.
Non-infectious diseases - These are all diseases, which are not caused by pathogens and cannot be passed on by physical contact. An example would be sickle cell anaemia.
Deficiency diseases- These are nutritional diseases caused by an inadequate or unbalanced diet. One or more essential nutrient is missing or in short supply - for example, a shortage of Vitamin C causes scurvy.
Categories of Disease 3
Inherited diseases - These diseases are caused by genes and can therefore be passed from parent to child. They are also sometimes called genetic diseases or disorders.
Degenerative diseases - These diseases are characterised by a gradual loss of function, in one or several organs or tissues. In old age, this is often the result of the failure of the bodies repair mechanisms - for example, loss of mobility due to worn joints.
Mental disorders - These disorders affect a person's mind, but may be accompanied by physical symptoms. Emotions, thoughts, memories and personal and social behaviour can be affected.
Social diseases - This is a very wide category that can include almost all infectious diseases and multifactorial diseases, which are influenced by people's living conditions and their personal behaviour. For example, deficiency diseases may be the result of lack of choice of food, due to shortage of money.
Self-inflicted diseases - These diseases are caused by damage to a person's health by their own decisions and behaviour. Included in this category would be the choice to smoke or misusing drugs, sunbathing or eating a high fat diet. Deliberate self-harm, such as attempted suicide, could also be placed here although it is often an indication of poor mental health.