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Encyclopedia > Transmission (medicine)

In medicine, transmission is the passing of a disease from an infected individual or group to a previously uninfected individual or group. The microorganisms (bacteria and viruses) that cause disease may be transmitted from one person to another by one or more of the following means: Medicine is the branch of health science and the sector of public life concerned with maintaining or restoring human health through the study, diagnosis, treatment and possible prevention of disease and injury. ... A disease or medical condition is an abnormality of the body or mind that causes discomfort, dysfunction, distress, or death to the person afflicted or those in contact with the person. ... Phyla/Divisions Actinobacteria Aquificae Bacteroidetes/Chlorobi Chlamydiae/Verrucomicrobia Chloroflexi Chrysiogenetes Cyanobacteria Deferribacteres Deinococcus-Thermus Dictyoglomi Fibrobacteres/Acidobacteria Firmicutes Fusobacteria Gemmatimonadetes Nitrospirae Omnibacteria Planctomycetes Proteobacteria Spirochaetes Thermodesulfobacteria Thermomicrobia Thermotogae Bacteria (singular, bacterium) are a major group of living organisms. ... Groups I: dsDNA viruses II: ssDNA viruses III: dsRNA viruses IV: (+)ssRNA viruses V: (-)ssRNA viruses VI: ssRNA-RT viruses VII: dsDNA-RT viruses A virus (Latin, poison) is a microscopic particle that can infect the cells of a biological organism. ...

  • droplet contact - coughing or sneezing on another person
  • direct physical contact - touching an infected person, including sexual contact
  • indirect contact - usually by touching soil contamination or a contaminated surface
  • airborne transmission - if the microorganism can remain in the air for long periods
  • fecal-oral transmission - usually from contaminated food or water sources
  • vector borne transmission - carried by insects or other animals

Microorganisms vary widely in the length of time that they can survive outside the human body, and so vary in how they are transmitted. This page meets Wikipedias criteria for speedy deletion. ...

Contents

Transmission, symptoms and survival

In order to survive, microorganisms that require human hosts must have a way to be transmitted from one host to another. Infectious agents are generally specialised for a particular method of transmission. Taking an example from the respiratory route, from an evolutionary perspective a virus or bacteria that causes its host to develop coughing and sneezing symptoms has a great survival advantage - it is much more likely to be ejected from one host and carried to another. This is also the reason that many microorganisms cause diarrhea. Diarrhea or diarrhoea (see American and British English spelling differences) is a condition in which the sufferer has frequent watery, loose bowel movements (from the ancient Greek word διαρροή = leakage; literally meaning to run through). Acute infectious diarrhea is a common cause of death in developing countries (particularly among infants), accounting...


Routes of transmission

Droplet contact

Also known as the respiratory route, it is a typical mode of transmission among many infectious agents. If an infected person coughs or sneezes on another person the microorganisms, suspended in warm, moist droplets, may enter the body through the nose, mouth or eye surfaces. Diseases that are commonly spread by coughing or sneezing include (at least):

Meningitis is the inflammation of the membranes (meninges) covering the brain, usually due to bacterial or viral infections elsewhere in the body that has spread into the blood and into the cerebrospinal fluid (CSF). ... For the South Park episode, see Chickenpox (South Park episode). ... Acute viral nasopharyngitis, often known as the common cold, is a mild viral infectious disease of the upper respiratory system (nose and throat). ... Influenza, commonly known as the flu, is an infectious disease that infects birds and mammals (primarily of the upper airways and lungs in mammals) and is caused by an RNA virus of the Orthomyxoviridae family (the influenza viruses). ... Strep throat (or Streptococcal pharyngitis, or Streptococcal Sore Throat) is a form of Group A streptococcal infection that affects the pharynx. ... Tuberculosis (abbreviated as TB for Tubercle Bacillus) is a common and deadly infectious disease caused by the bacterium Mycobacterium tuberculosis, which most commonly affects the lungs (pulmonary TB) but can also affect the central nervous system, lymphatic system, circulatory system, genitourinary system, bones and joints. ...

Fecal-oral transmission

Direct contact is rare in this route, for humans at least. More common are the indirect routes; foodstuffs or water become contaminated (by people not washing their hands before preparing food, or untreated sewage being released into a drinking water supply) and the people who eat and drink them become infected. In developing countries most sewage is discharged into the environment or on cropland as of 2006; even in developed countries there are periodic system failures resulting in a sanitary sewer overflow. This is the typical mode of transmission for the infectious agents of (at least): A developing country is a country with low average income compared to the world average. ... A developed country is a country that has achieved (currently or historically) a high degree of industrialization, and which enjoys the higher standards of living which wealth and technology make possible. ... Decentralized wet weather overflow event Sanitary sewer overflow (SSO} is a condition whereby untreated sewage is discharged into the environment, escaping wastewater treatment. ...

Cholera (also called Asiatic cholera) is a water-borne disease caused by the bacterium Vibrio cholerae, which is typically ingested by drinking contaminated water, or by eating improperly cooked fish, especially shellfish. ... Hepatitis A is an enterovirus transmitted by the orofecal route, such as contaminated food. ... Poliomyelitis (polio), or infantile paralysis, is a viral paralytic disease. ... Species Rotavirus A (RV-A) Rotavirus B (RV-B) Rotavirus C (RV-C) Rotavirus D (RV-D) Rotavirus E (RV-E) Rotavirus F (RV-F) Rotavirus G (RV-G) Rotaviruses are a genus of viruses belonging to the Reoviridae family. ...

Sexual transmission

This refers to any disease that can be caught during sexual activity with another person, including vaginal or anal sex or (less commonly) through oral sex (see below). Transmission is either directly between surfaces in contact during intercourse (the usual route for bacterial infections and those infections causing sores) or from secretions (semen or the fluid secreted by the excited female) which carry infectious agents that get into the partner's blood stream through tiny tears in the penis, vagina or rectum (this is a more usual route for viruses). In this second case, anal sex is considerably more hazardous since penis opens more tears in the rectum than the vagina, as the vagina is stretchier and more accommodating. Coition of a Hemisected Man and Woman (c. ... Roman men having anal sex. ... Oral sex (from Latin os, oris mouth) consists of all the sexual activities that involve the use of the mouth and tongue, to stimulate genitalia. ... Phyla/Divisions Actinobacteria Aquificae Bacteroidetes/Chlorobi Chlamydiae/Verrucomicrobia Chloroflexi Chrysiogenetes Cyanobacteria Deferribacteres Deinococcus-Thermus Dictyoglomi Fibrobacteres/Acidobacteria Firmicutes Fusobacteria Gemmatimonadetes Nitrospirae Omnibacteria Planctomycetes Proteobacteria Spirochaetes Thermodesulfobacteria Thermomicrobia Thermotogae Bacteria (singular, bacterium) are a major group of living organisms. ... Human semen Horse semen being collected for breeding purposes. ... The penis (plural penises, penes) is an external male sexual organ. ... The vagina, (from Latin, literally sheath or scabbard ) is the tubular tract leading from the uterus to the exterior of the body in female placental mammals and marsupials, or to the cloaca in female birds, monotremes, and some reptiles. ... The posterior aspect of the rectum exposed by removing the lower part of the sacrum and the coccyx. ... Groups I: dsDNA viruses II: ssDNA viruses III: dsRNA viruses IV: (+)ssRNA viruses V: (-)ssRNA viruses VI: ssRNA-RT viruses VII: dsDNA-RT viruses A virus (Latin, poison) is a microscopic particle that can infect the cells of a biological organism. ...


Some diseases transmissible by the sexual route include (at least):

Acquired Immune Deficiency Syndrome (AIDS or Aids) is a collection of symptoms and infections in humans resulting from the specific damage to the immune system caused by the human immunodeficiency virus (HIV). ... Chlamydia is a common term for infection with any bacteria belonging to the phylum Chlamydiae. ... Genital warts or (or condyloma) is a very contagious sexually transmitted disease. ... Gonorrhoea (USA spelling: gonorrhea, slang term the clap) is among the most common curable sexually transmitted diseases in the world caused by the Gram-negative bacterium called Neisseria gonorrhoeae. ... Hepatitis B is a disease of the liver caused by the Hepatitis B virus (HBV), a member of the Hepadnavirus family[1] and one of several unrelated viral species which cause viral hepatitis. ... Syphilis is a sexually transmitted infection (STI) caused by a spirochaete bacterium, Treponema pallidum. ...

Oral sexual transmission

Sexually Transmitted Diseases such as HIV and Hepatitis B are thought to not normally be transmitted through mouth-to-mouth contact, although it is possible to transmit some STDs between the genitals and the mouth, during oral sex. In the case of HIV this possibility has been established. It is also responsible for the increased incidence of herpes simplex virus 1 (which is usually responsible for oral infections) in genital infections and the increased incidence of the type 2 virus (more common genitally) in oral infections. Sexually transmitted diseases (STDs) — also known as sexually transmissible diseases, sexually transmitted infections (STIs) or (infrequently) venereal diseases (VD) or social disease — are diseases or infections that have a significant probability of transmission between humans by means of sexual contact, vaginal intercourse, oral sex, and/or anal sex. ... Human immunodeficiency virus or HIV is a retrovirus that causes Acquired Immunodeficiency Syndrome (AIDS), a condition in which the immune system begins to fail, leading to life-threatening opportunistic infections. ... Hepatitis B is a disease of the liver caused by the Hepatitis B virus (HBV), a member of the Hepadnavirus family[1] and one of several unrelated viral species which cause viral hepatitis. ... Human immunodeficiency virus or HIV is a retrovirus that causes Acquired Immunodeficiency Syndrome (AIDS), a condition in which the immune system begins to fail, leading to life-threatening opportunistic infections. ... The herpes simplex virus (HSV) is a virus that manifests itself in two common viral infections, each marked by painful, watery blisters in the skin or mucous membranes (such as the mouth or lips) or on the genitals. ...


Oral transmission

Diseases that are transmitted primarily by oral means may be caught through direct oral contact such as kissing, or by indirect contact such as by sharing a drinking glass or a cigarette. The Kiss by Francesco Hayez, 19th century. ...


Diseases that are known to be transmissible by kissing or by other direct or indirect oral contact include all of the diseases listed above as transmissible by droplet contact and also (at least):

(Notice these are all forms of herpes virus.) Species see text Cytomegalovirus (CMV), is a genus of Herpes viruses; in humans the species is known as Human herpesvirus 5 (HHV-5). ... The herpes simplex virus (HSV) is a virus that manifests itself in two common viral infections, each marked by painful, watery blisters in the skin or mucous membranes (such as the mouth or lips) or on the genitals. ... Infectious mononucleosis (also known in North America as mono, the kissing disease or Pfeiffers disease, and more commonly known as glandular fever in other English-speaking countries) is a disease seen most commonly in adolescents and young adults, characterized by fever, sore throat and fatigue. ... Genera Subfamily Alphaherpesvirinae    Simplexvirus    Varicellovirus    Mardivirus    Iltovirus Subfamily Betaherpesvirinae    Cytomegalovirus    Muromegalovirus    Roseolovirus Subfamily Gammaherpesvirinae    Lymphocryptovirus    Rhadinovirus Unassigned    Ictalurivirus The Herpesviridae is a family of DNA viruses that cause diseases in humans and animals. ...


Transmission by direct contact

Diseases that can be transmitted by direct contact are called contagious (contagious is not the same as infectious; although all contagious diseases are infectious, not all infectious diseases are contagious). These diseases can also be transmitted by sharing a towel (where the towel is rubbed vigorously on both bodies) or items of clothing in close contact with the body (socks, for example) if they are not washed thoroughly between uses. For this reason, contagious diseases often break out in schools, where towels are shared and personal items of clothing accidentally swapped in the changing rooms.


Some diseases that are transmissible by direct contact include:

Athletes foot or tinea pedis is a fungal infection of the skin of the foot, usually between the toes, caused by parasitic fungi. ... Syphilis is a sexually transmitted infection (STI) caused by a spirochaete bacterium, Treponema pallidum. ... Primary syphilis is manifested after an incubation period of 10-90 days (average 21 days) after exposure with a primary sore. ... It has been suggested that this article or section be merged with Plantar wart. ...

Vertical transmission

This is from mother to child, often in utero, as a result of the incidental exchange of bodily fluids (mostly blood) during childbirth or (rarely) through breast milk. Childbirth (also called labour, birth, partus or parturition) is the culmination of a human pregnancy with the emergence of a newborn infant from its mothers uterus. ... Wean redirects here: see #Weaning. ...


Some diseases that can be transmitted in this way include:

Acquired Immune Deficiency Syndrome (AIDS or Aids) is a collection of symptoms and infections in humans resulting from the specific damage to the immune system caused by the human immunodeficiency virus (HIV). ... Hepatitis B is a disease of the liver caused by the Hepatitis B virus (HBV), a member of the Hepadnavirus family[1] and one of several unrelated viral species which cause viral hepatitis. ... Syphilis is a sexually transmitted infection (STI) caused by a spirochaete bacterium, Treponema pallidum. ...

Iatrogenic transmission

Transmission due to medical procedures, such as injection or transplantation of infected material. An iatrogenic (pronounced , IPA) condition is a state of ill health or adverse effect caused by medical treatment, usually due to mistakes made in treatment. ... An injection is a method of putting liquid into the body with a hollow needle and a syringe which is pierced through the skin long enough for the material to be forced into the body. ... An organ transplant is the transplantation of a whole or partial organ from one body to another (or from a donor site on the patients own body), for the purpose of replacing the recipients damaged or failing organ with a working one from the donor site. ...


Some diseases that can be transmitted iatrogenically include:

  • Creutzfeldt-Jakob Disease by injection of contaminated human growth hormone.
  • MRSA infection is often acquired as a result of a stay in hospital

The route of transmission is important to epidemiologists because patterns of contact vary between different populations and different groups of populations depending on socio-economic, cultural and other features. For example, low personal and food hygiene due to the lack of a clean water supply may result in increased transmission of diseases by the fecal-oral route, such as cholera. Differences in incidence of such diseases between different groups can also throw light on the routes of transmission of the disease. For example, if it is noted that polio is more common in cities in underdeveloped countries, without a clean water supply, than in cities with a good plumbing system, we might advance the theory that polio is spread by the fecal-oral route. Creutzfeldt-Jakob disease (CJD) is a very rare and incurable degenerative neurological disorder (brain disease) that is ultimately fatal. ... Growth hormone Growth hormone (GH or somatotropin) is a polypeptide hormone synthesised and secreted by the anterior pituitary gland which stimulates growth and cell reproduction in humans and other vertebrate animals. ... MRSA, or methicillin-resistant Staphylococcus aureus, is a bacterium that has developed antibiotic resistance, first to penicillin in 1947, and later to methicillin. ... Epidemiology is the scientific study of factors affecting the health and illness of individuals and populations, and serves as the foundation and logic of interventions made in the interest of public health and preventive medicine. ... Cholera (also called Asiatic cholera) is a water-borne disease caused by the bacterium Vibrio cholerae, which is typically ingested by drinking contaminated water, or by eating improperly cooked fish, especially shellfish. ... Poliomyelitis (polio), or infantile paralysis, is a viral paralytic disease. ...


See also

In medicine, infectious disease or communicable disease is disease caused by a biological agent such as by a virus, bacterium or parasite. ...

External links

  • Oral HIV Infection

  Results from FactBites:
 
Medicine - Encyclopedia, History, Geography and Biography (4724 words)
Medicine is the branch of health science and the sector of public life concerned with maintaining or restoring human health through the study, diagnosis and treatment of disease and injury.
Medicine as it is practiced now developed largely in the late eighteenth century and early nineteenth century in England (William Harvey, seventeenth century), Germany (Rudolf Virchow) and France (Jean-Martin Charcot, Claude Bernard and others).
Evidence-based medicine is a recent movement to establish the most effective algorithms of practice (ways of doing things) through the use of the scientific method and modern global information science by collating all the evidence and developing standard protocols which are then disseminated to doctors.
HIV (4025 words)
One case was reported of transmission from an HlV-infected hemophiliac to his twin hemophiliac brother, which may have resulted from a shared razor." A second case was documented of transmission of the HIV from an HlV-infected child to an HIVseronegative child.
This absence of documented cases of transmission during athletic activity is significant in view of the known prevalence of HIV infection.
The HIV transmission is documented to occur in approximately 1 of 300 needle-stick injuries involving infected blood.
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