A disease is an abnormal condition affecting the body of an organism. It is often construed to be a medical condition associated with specific symptoms A symptom is a departure from normal function or feeling which is noticed by a patient, indicating the presence of disease or abnormality. A symptom is subjective, observed by the patient, and not measured and signs A medical sign is an objective indication of some medical fact or characteristic that may be detected by a physician during a physical examination of a patient.^[1][2][3] It may be caused by external factors, such as infectious disease An infectious disease is a clinically evident illness resulting from the presence of pathogenic microbial agents, including pathogenic viruses, pathogenic bacteria, fungi, protozoa, multicellular parasites, and aberrant proteins known as prions. These pathogens are able to cause disease in animals and/or plants. Infectious pathologies are also, or it may be caused by internal disfunctions, such as autoimmune diseases Autoimmune diseases arise from an overactive immune response of the body against substances and tissues normally present in the body. In other words, the body actually attacks its own cells. The immune system mistakes some part of the body as a pathogen and attacks it. This may be restricted to certain organs or involve a particular tissue in.

In humans, "disease" is often used more broadly to refer to any condition that causes pain Pain is an unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage. It is the feeling common to such experiences as stubbing a toe, burning a finger, putting iodine on a cut, and bumping the "funny bone", dysfunction, distress, social problems Social issues are matters which directly or indirectly affect many or all members of a society and are considered to be problems, controversies related to moral values, or both, and/or death Death is the termination of the biological functions that define a living organism. The word refers both to a particular process and to the condition that results thereby. The nature of the latter has been for millennia a central concern of the world's religious traditions and of philosophical enquiry. Belief in some kind of afterlife or rebirth to the person afflicted, or similar problems for those in contact with the person. In this broader sense, it sometimes includes injuries Injury is damage or harm caused to the structure or function of the body caused by an outside agent or force, which may be physical or chemical, and either by accident or intentional. Personal Injury also refers to damage caused to the reputation of another rather than physical harm to the body. A severe and life-threatening injury is referred to, disabilities The World Health Organization defines Disability as follows: "Disabilities is an umbrella term, covering impairments, activity limitations, and participation restrictions. An impairment is a problem in body function or structure; an activity limitation is a difficulty encountered by an individual in executing a task or action; while a, disorders A disease or medical condition is an abnormal condition of an organism that impairs bodily functions, associated with specific symptoms and signs. It may be caused by external factors, such as infectious disease, or it may be caused by internal dysfunctions, such as autoimmune diseases, syndromes In medicine and psychology, a syndrome is the association of several clinically recognizable features, signs , symptoms (reported by the patient), phenomena or characteristics that often occur together, so that the presence of one feature alerts the physician to the presence of the others. In recent decades, the term has been used outside medicine, infections An infection is the detrimental colonization of a host organism by a foreign species. In an infection, the infecting organism seeks to utilize the host's resources to multiply, usually at the expense of the host. The infecting organism, or pathogen, interferes with the normal functioning of the host and can lead to chronic wounds, gangrene, loss. Isolated symptoms A symptom is a departure from normal function or feeling which is noticed by a patient, indicating the presence of disease or abnormality. A symptom is subjective, observed by the patient, and not measured, deviant behaviors Behavior, or behaviour , refers to the actions of an organism or system, usually in relation to its environment, which includes the other organisms or systems around as well as the physical environment. It is the response of the organism or system to various stimuli or inputs, whether internal or external, conscious or subconscious, overt or, and atypical variations Human variability, or human variation, is the range of possible values for any measurable characteristic, physical or mental, of human beings. Differences can be trivial or important, transient or permanent, voluntary or involuntary, congenital or acquired, genetic or environmental. This article discusses variabilities that characterize a person of structure and function, while in other contexts and for other purposes these may be considered distinguishable categories. A diseased body is quite often not only because of some dysfunction of a particular organ In biology and anatomy, an organ is a collection of tissues joined in structural unit to serve a common function but can also be because of a state of mind Mind is the aspect of intellect and consciousness experienced as combinations of thought, perception, memory, emotion, will and imagination, including all unconscious cognitive processes. The term is often used to refer, by implication, to the thought processes of reason. Mind manifests itself subjectively as a stream of consciousness of the affected person who is not at ease with a particular state of its body.

Death due to disease is called death by natural causes In medicine, death by natural causes is a loosely defined term used by coroners to describe death when the cause was disease instead of violence or drug use. It is also used when the cause is unknown. It may also refer to death by multiple organ dysfunction syndrome.

Terminology

In many cases, the terms disease, disorder, morbidity and illness are used interchangeably.^[4] In some situations, specific terms are considered preferable.

Infection

This term broadly refers to any abnormal condition that impairs normal function. Commonly, this term is used to refer specifically to infectious diseases An infectious disease is a clinically evident illness resulting from the presence of pathogenic microbial agents, including pathogenic viruses, pathogenic bacteria, fungi, protozoa, multicellular parasites, and aberrant proteins known as prions. These pathogens are able to cause disease in animals and/or plants. Infectious pathologies are also, which are clinically evident diseases that result from the presence of pathogenic A pathogen, (from Greek πάθος pathos "suffering, passion", and γἰγνομαι gignomai (gen-) "I give birth to") an infectious agent, or more commonly germ, is a biological agent that causes disease to its host. There are several substrates and pathways whereby pathogens can invade a host; the principal pathways have microbial agents, including viruses, bacteria, fungi, protozoa, multicellular parasites, and aberrant proteins known as prions. An infection An infection is the detrimental colonization of a host organism by a foreign species. In an infection, the infecting organism seeks to utilize the host's resources to multiply, usually at the expense of the host. The infecting organism, or pathogen, interferes with the normal functioning of the host and can lead to chronic wounds, gangrene, loss that does not produce clinically evident impairment of normal functioning is not considered a disease. Non-infectious diseases Non-infectious diseases are those diseases that are not caused by a pathogen and cannot be shared from one person to another. Diseases caused by these organisms are infectious diseases. There are many kinds of non-infectious diseases are all other diseases, including most forms of cancer Cancer /ˈkænsər/ (medical term: malignant neoplasm) is a class of diseases in which a group of cells display uncontrolled growth (division beyond the normal limits), invasion (intrusion on and destruction of adjacent tissues), and sometimes metastasis (spread to other locations in the body via lymph or blood). These three malignant properties, heart disease Heart disease or cardiopathy is an umbrella term for a variety of different diseases affecting the heart. As of 2007, it is the leading cause of death in the United States, England, Canada and Wales, killing one person every 34 seconds in the United States alone.[verification needed], and genetic disease A genetic disorder is an illness caused by abnormalities in genes or chromosomes. While some diseases, such as cancer, are due in part to a genetic disorders, they can also be caused by environmental factors. Most disorders are quite rare and affect one person in every several thousands or millions. Some types of recessive gene disorders confer an.

Illness

Illness Illness is a state of poor health. Illness is sometimes considered a synonym for disease. Others maintain that fine distinctions exist. Some have described illness as the subjective perception by a patient of an objectively defined disease and sickness are generally used as synonyms for disease.^[5] However, this term is occasionally used to refer specifically to the patient's personal experience of his or her disease.^[6][7] In this model, it is possible for a person to be diseased without being ill, (to have an objectively definable, but asymptomatic, medical condition), and to be ill without being diseased (such as when a person perceives a normal experience as a medical condition, or medicalizes Medicalization is the process by which human conditions and problems come to be defined and treated as medical conditions and problems, and thus come under the authority of doctors and other health professionals to study, diagnose, prevent or treat. The process of medicalization can be driven by new evidence or theories about conditions, or by a non-disease situation in his or her life). Illness is often not due to infection but a collection of evolved responses Evolutionary medicine or Darwinian medicine is the application of modern evolutionary theory to understanding health and disease. It provides a complementary scientific approach to the present mechanistic explanations that dominate medical science, and particularly modern medical education. Researchers in the field of evolutionary medicine have, sickness behavior Sickness behavior is a coordinated set of adaptive behavioral changes that develop in ill individuals during the course of an infection. They usually accompany fever and aid survival. Such illness responses include lethargy, depression, anorexia, sleepiness, hyperalgesia, reduction in grooming and failure to concentrate. Sickness behavior is a, by the body aids the clearing of infection. Such aspects of illness can include lethargy Fatigue is a state of awareness. It can describe a range of afflictions, varying from a general state of lethargy to a specific work-induced burning sensation within one's muscles. It can be both physical and mental. Physical fatigue is the inability to continue functioning at the level of one's normal abilities. It is ubiquitous in everyday life,, depression Depression is a state of low mood and aversion to activity. The Diagnostic and Statistical Manual of Mental Disorders defines a depressed person as experiencing feelings of sadness, helplessness and hopelessness. In traditional colloquy, feeling "depressed" is often synonymous with feeling "sad", but both clinical depression, anorexia Anorexia (deriving from the Greek "α-" (a(n)-, a prefix that denotes absence) + "όρεξη" (orexe) = appetite) is the decreased sensation of appetite. While the term in non-scientific publications is often used interchangeably with anorexia nervosa, many possible causes exist for a decreased appetite, some of which may be, sleepiness Somnolence is a state of near-sleep, a strong desire for sleep, or sleeping for unusually long periods (c.f. hypersomnia). It has two distinct meanings, referring both to the usual state preceding falling asleep, and the chronic condition referring to being in that state independent of a circadian rhythm. The disorder characterized by the latter, hyperalgesia Hyperalgesia is an increased sensitivity to pain, which may be caused by damage to nociceptors or peripheral nerves. Temporary increased sensitivity to pain also occurs as part of sickness behavior, the evolved response to infection, and inability to concentrate Attention is the cognitive process of selectively concentrating on one aspect of the environment while ignoring other things. Attention has also been referred to as the allocation of processing resources.^[8][9][10]

Disorder

In medicine, a disorder is a functional abnormality or disturbance.^[11] Medical disorders can be categorized into mental disorders A mental disorder or mental illness is a psychological or behavioral pattern associated with distress or disability that occurs in an individual and is not a part of normal development or culture. The recognition and understanding of mental health conditions has changed over time and across cultures, and there are still variations in the, physical disorders A physical disorder is often used as a term in contrast to a mental disorder, in an attempt to differentiate medical disorders that have an available objective mechanical test (such as chemical tests or brain scans), from those disorders which have no objective laboratory or imaging test, and are diagnosed only by behavioral syndrome (such as, genetic disorders A genetic disorder is an illness caused by abnormalities in genes or chromosomes. While some diseases, such as cancer, are due in part to a genetic disorders, they can also be caused by environmental factors. Most disorders are quite rare and affect one person in every several thousands or millions. Some types of recessive gene disorders confer an, emotional and behavioral disorders Emotional and behavioral disorders is a broad category which is used commonly in educational settings, to group a range of more specific perceived difficulties of children and adolescents. Both general definitions as well as concrete diagnosis of EBD may be controversial as the observed behavior may depend on many factors, and functional disorders A functional disorder is a medical condition that impairs the normal function of a bodily process. Definitions vary between fields of medicine, with orthopedics using it to describe a structural defect, such as a misshapen bone, and psychiatry and neurology using it to mean an emotional disorder. Sometimes, the term functional disorder is used to.

The term disorder is often considered more value-neutral and less stigmatizing than the terms disease or illness, and therefore is preferred terminology in some circumstances. In mental health, the term mental disorder A mental disorder or mental illness is a psychological or behavioral pattern associated with distress or disability that occurs in an individual and is not a part of normal development or culture. The recognition and understanding of mental health conditions has changed over time and across cultures, and there are still variations in the is used as a way of acknowledging the complex interaction of biological, social, and psychological factors The biopsychosocial model is a general model or approach that posits that biological, psychological (which entails thoughts, emotions, and behaviors), and social factors, all play a significant role in human functioning in the context of disease or illness. Indeed, health is best understood in terms of a combination of biological, psychological, in psychiatric Psychiatry is the medical specialty devoted to the study and treatment of mental disorders—which include various affective, behavioural, cognitive and perceptual disorders. The term was first coined by the German physician Johann Christian Reil in 1808. It literally means the 'medical treatment of the mind' . A medical doctor specializing in conditions. However, the term disorder is also used in many other areas of medicine, primarily to identify physical disorders that are not caused by infectious organisms, such as organic brain syndrome Organic brain syndrome is an older and nearly obsolete general term from psychiatry, referring to many physical disorders that cause impaired mental function. It usually does not include psychiatric disorders. Originally, the term was created to distinguish physical (termed "organic") causes of mental impairment from psychiatric (termed &.

Medical condition

A medical condition is a broad term that includes all diseases and disorders, but can include [injuries] and normal health situations, such as pregnancy Pregnancy is the carrying of one or more offspring, known as a fetus or embryo, inside the womb of a female. In a pregnancy, there can be multiple gestations, as in the case of twins or triplets. Human pregnancy is the most studied of all mammalian pregnancies. Childbirth usually occurs about 38 weeks after conception; i.e., approximately 40 weeks, that might affect a person's health, benefit from medical assistance, or have implications for medical treatments. While the term medical condition generally includes mental illnesses, in some contexts the term is used specifically to denote any illness, injury, or disease except for mental illnesses. The Diagnostic and Statistical Manual of Mental Disorders The Diagnostic and Statistical Manual of Mental Disorders is published by the American Psychiatric Association and provides a common language and standard criteria for the classification of mental disorders. It is used in the United States and in varying degrees around the world, by clinicians, researchers, psychiatric drug regulation agencies, (DSM), the widely used psychiatric manual that defines all mental disorders A mental disorder or mental illness is a psychological or behavioral pattern associated with distress or disability that occurs in an individual and is not a part of normal development or culture. The recognition and understanding of mental health conditions has changed over time and across cultures, and there are still variations in the, uses the term general medical condition to refer to all diseases, illnesses, and injuries except for mental disorders A mental disorder or mental illness is a psychological or behavioral pattern associated with distress or disability that occurs in an individual and is not a part of normal development or culture. The recognition and understanding of mental health conditions has changed over time and across cultures, and there are still variations in the.^[12] This usage is also commonly seen in the psychiatric literature. Some health insurance Health insurance, like other forms of insurance, is a form of collectivism by means of which people collectively pool their risk, in this case the risk of incurring medical expenses. The collective is usually publicly owned or else is organized on a non-profit basis for the members of the pool, though in some countries health insurance pools may policies also define a medical condition as any illness, injury, or disease except for psychiatric illnesses.^[13]

As it is more value-neutral A value judgment is a judgment of the rightness or wrongness of something, or of the usefulness of something, based on a personal view. As a generalization, a value judgment can refer to a judgment based upon a particular set of values or on a particular value system. A related meaning of value judgment is an expedient evaluation based upon than terms like disease, the term medical condition is sometimes preferred by people with health issues that they do not consider to be deleterious, such as pregnancy. On the other hand, by emphasizing the medical nature of the condition, this term is sometimes rejected, such as by proponents of the autism rights movement.

The term medical condition is used as a synonym for medical state, where it describes a patient's current state, as seen from a medical standpoint. This usage is seen in statements that describe a patient as being "in critical condition", for example.

Morbidity

Morbidity (from Latin morbidus: sick, unhealthy) refers to a diseased state, disability, or poor health due to any cause.^[14] The term may be used to refer to the existence of any form of disease, or to the degree that the health condition affects the patient. Among severely ill patients, the level of morbidity is often measured by ICU scoring systems.

Comorbidity is the simultaneous presence of two medical conditions, such as a person with schizophrenia and substance abuse.

In epidemiology and actuarial science, the term morbidity rate can refer to either the incidence rate, or the prevalence of a disease or medical condition. This measure of sickness is contrasted with the mortality rate of a condition, which is the proportion of people dying during a given time interval.

Stages

In an infectious disease, the incubation period is the time between infection and the appearance of symptoms. The latency period is the time between infection and the ability of the disease to spread to another person, which may precede, follow, or be simultaneous with the appearance of symptoms. Some viruses also exhibit a dormant phase, called viral latency, in which the virus hides in the body in an inactive state. For example, varicella zoster virus causes chickenpox in the acute phase; after recovery from chickenpox, the virus may remain dormant in nerve cells for many years, and later cause herpes zoster (shingles).

A cure is the end of a medical condition or a treatment that is very likely to end it, while remission refers to the disappearance, possibly temporarily, of symptoms. Complete remission is the best possible outcome for incurable diseases.

A flare-up can refer to either the recurrence of symptoms or an onset of more severe symptoms.

A refractory disease is a disease that resists treatment, especially an individual case that resists treatment more than is normal for the specific disease in question.

Scope

A localized disease is one that affects only one part of the body, such as athlete's foot or an eye infection.

A disseminated disease has spread to other parts; with cancer, this is usually called metastatic disease.

A systemic disease is a disease that affects the entire body, such as influenza or high blood pressure.

Disease transmission

Only some diseases such as influenza are contagious and commonly believed to be infectious. The micro-organisms that cause these diseases are known as pathogens and include varieties of bacteria, viruses, protozoa and fungi. Infectious diseases can be transmitted, e.g. by hand-to-mouth contact with infectious material on surfaces, by bites of insects or other carriers of the disease, and from contaminated water or food (often via faecal contamination), etc. In addition, there are sexually transmitted diseases. In some cases, micro-organisms that are not readily spread from person to person play a role, while other diseases can be prevented or ameliorated with appropriate nutrition or other lifestyle changes. It is being found lately that some diseases are more common in some geographical locations (Cities) only. All people in an epidemic zone are not equally affected with the infectious disease. Also it is not really understood why a person starts suffering from a disease at a particular point in time, often immunity is invoked as the reason, but it is quite possible that the microbial population which differs from person to person may be responsible.^[15]

Some diseases, such as most (but not all) forms of cancer, heart disease and mental disorders, are non-infectious diseases. Many non-infections diseases have a partly or completely genetic basis (see genetic disorder) and may thus be transmitted from one generation to another.

Social significance of disease

A condition may be considered to be a disease in some cultures or eras but not in others. Conditions such as attention-deficit hyperactivity disorder and obesity are considered to be diseases by some developed countries, but have been regarded differently in other cultures. For example, obesity can also represent wealth and abundance, and is a status symbol in famine-prone areas and some places hard-hit by HIV/AIDS.^[17]

Sickness confers the social legitimization of certain benefits, such as illness benefits, work avoidance, and being looked after by others. In return, there is an obligation on the sick person to seek treatment and work to become well once more. As a comparison, consider pregnancy, which is not usually interpreted as a disease or sickness by the individual. On the other hand, it is considered by the medical community as a condition requiring medical care.

The identification of a condition as a disease, rather than as simply a variation of human structure or function, can have significant social or economic implications. The controversial recognitions as diseases of post-traumatic stress disorder, also known as "Soldier's heart", "shell shock", and "combat fatigue;" repetitive motion injury or repetitive stress injury (RSI); and Gulf War syndrome has had a number of positive and negative effects on the financial and other responsibilities of governments, corporations and institutions towards individuals, as well as on the individuals themselves. The social implication of viewing aging as a disease could be profound, though this classification is not yet widespread. Lepers were a group of afflicted individuals who were historically shunned and the term "leper" still evokes social stigma. Fear of disease can still be a widespread social phenomenon, though not all diseases evoke extreme social stigma.

Social standing and economic status affect health. Diseases of poverty are diseases that are associated with poverty and low social status; diseases of affluence are diseases that are associated with high social and economic status. Which diseases are associated with which states varies according to time, place, and technology. Some diseases, such as diabetes mellitus, may be associated with both poverty (poor food choices) and affluence (long lifespans and sedentary lifestyles), through different mechanisms. The term diseases of civilization describes diseases that are more common among older people. For example, cancer is far more common in societies in which most members live until they reach the age of 80 than in societies in which most members die before they reach the age of 50.

See also

• List of acronyms on diseases and disorders
• List of cutaneous conditions
• Lists of diseases
• Progressive disease
• Rare disease
• Epidemiology

References

1. ^ eMedicine/Stedman Medical Dictionary Lookup!
2. ^ Disease at Dorland's Medical Dictionary
3. ^ WordNet Search - 3.0
4. ^ "Mental Illness—Glossary". Science.education.nih.gov. http://science.education.nih.gov/supplements/nih5/mental/other/glossary.htm. Retrieved 2010-04-18.
5. ^ Illness at Dorland's Medical Dictionary
6. ^ Emson HE (April 1987). "Health, disease and illness: matters for definition". CMAJ 136 (8): 811–3. PMID 3567788.
7. ^ McWhinney IR (April 1987). "Health and disease: problems of definition". CMAJ 136 (8): 815. PMID 3567791.
8. ^ Hart, B. L. (1988) "Biological basis of the behavior of sick animals". Neurosci Biobehav Rev. 12: 123-137. PubMed
9. ^ Johnson, R. (2002) "The concept of sickness behavior: a brief chronological account of four key discoveries". Veterinary Immunology and Immunopathology. 87: 443-450 PubMed
10. ^ Kelley, K. W., Bluthe, R. M., Dantzer, R., Zhou, J. H., Shen, W. H., Johnson, R. W. Broussard, S. R. (2003) "Cytokine-induced sickness behavior". Brain Behav Immun. 17 Suppl 1: S112-118 PubMed
11. ^ eMedicine/Stedman Medical Dictionary
12. ^ American Psychiatric Association. (2000). Diagnostic and statistical manual of mental disorders, (4th ed., text revision). Washington, DC: American Psychiatric Association.
13. ^ "Expat Insurance Glossary by The Insurance Page". http://www.theinsurancepage.co.uk/expat-insurance-glossary.html. Retrieved 2008-11-20.
14. ^ Dorland's Medical Dictionary: morbidity, Dorland's Medical Dictionary, MerckSource
15. ^ http://www.scribd.com/doc/34140453/Disease-Immunity-and-Microbes
16. ^ Carol Gerten-Jackson. "The Tuscan General Alessandro del Borro". http://www.cab.u-szeged.hu/cgfa/m/m-12.htm.
17. ^ Haslam DW, James WP (2005). "Obesity". Lancet 366 (9492): 1197–209. doi:10.1016/S0140-6736(05)67483-1. PMID 16198769.

External links

• Health Topics, MedlinePlus descriptions of most diseases, with access to current research articles.
• OMIM Comprehensive information on genes that cause disease at Online Mendelian Inheritance in Man
• CTD The Comparative Toxicogenomics Database is a scientific resource connecting chemicals, genes, and human diseases.
• NLM Comprehensive database from the US National Library of Medicine
• Health Topics A-Z, fact sheets about many common diseases at Center for Disease Control
• The Merck Manual containing detailed description of most diseases
• Report: The global burden of disease from World Health Organization (WHO), 2004
• What is in the Diseases Database? Diseases Database

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