Editing Pathogen transmission (section)

===Direct contact===
{{Further|Contagious disease}}
Direct contact occurs through skin-to-skin contact, kissing, and sexual intercourse. Direct contact also refers to contact with soil or vegetation harboring infectious organisms.<ref name=":1">{{Cite web|date=2019-02-18|title=Principles of Epidemiology: Chain of Infection|url=https://www.cdc.gov/csels/dsepd/ss1978/lesson1/section10.html|access-date=2020-07-21|website=U.S. Centers for Disease Control and Infection|language=en-us}} {{PD-inline}}</ref>  Additionally, while fecal–oral transmission is primarily considered an indirect contact route, direct contact can also result in transmission through feces.<ref name=":2">{{Cite web| vauthors = LaMorte WW |date=2016-01-06|title=Common Vehicle Spread|url=https://sphweb.bumc.bu.edu/otlt/MPH-Modules/PH/PH709_Transmission/PH709_Transmission5.html|access-date=2020-07-21|website=Boston University School of Public Health}}</ref><ref name=":3">{{cite encyclopedia | vauthors = Whittier CA |title=Fecal-Oral Transmission|date=2017-04-16|encyclopedia=The International Encyclopedia of Primatology|pages=1| veditors = Bezanson M, MacKinnon KC, Riley E, Campbell CJ |place=Hoboken, NJ, USA|publisher=John Wiley & Sons, Inc.|language=en|doi=10.1002/9781119179313.wbprim0193|isbn=978-1-119-17931-3 }}</ref>

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.{{cn|date=June 2021}}

Some diseases that are transmissible by direct contact include [[athlete's foot]], [[impetigo]], syphilis, [[wart]]s, and [[conjunctivitis]].<ref>{{cite book |title=Jawetz, Melnick & Adelberg's Medical Microbiology |date=2019 |location=New York | publisher = McGraw-Hill Education |isbn=978-1-260-01202-6 |edition=28th| vauthors = Morse SA, Mietzner TA, Miller S, Riedel S }}</ref>

====Sexual====
{{main|Sexually transmitted infection}}
This refers to any infection that can be caught during sexual activity with another person, including [[sexual intercourse|vaginal]] or [[anal sex]], less commonly through [[oral sex]] (see below) and rarely through [[Non-penetrative sex#Manual sex|manual sex]] (see below). Transmission is either directly between surfaces in contact during intercourse (the usual route for [[bacterium|bacteria]]l 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 [[Human penis|penis]], [[vagina]] or [[rectum]] (this is a more usual route for [[virus]]es). In this second case, anal sex is considerably more hazardous since the penis opens more tears in the rectum than the vagina, as the vagina is more elastic and more accommodating.{{citation needed|date=September 2015}}

Some infections transmissible by the sexual route include [[AIDS|HIV/AIDS]], [[Chlamydia infection|chlamydia]], [[genital warts]], [[gonorrhea]], [[hepatitis B]], [[syphilis]], [[herpes]], and [[trichomoniasis]].{{cn|date=June 2021}}

====Oral sex====
[[Sexually transmitted infection]]s 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 STIs 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.{{citation needed|date=September 2015}}

====Manual sex====
While rare in regards to this sexual practice, some infections that can spread via manual sex include [[Human papillomavirus infection|HPV]], chlamydia, and syphilis.<ref>{{cite book| last1 = Hoyle | first1 = Alice | last2 = McGeeney | first2 = Ester |title=Great Relationships and Sex Education|publisher=Taylor and Francis|year=2019|access-date=July 11, 2023|isbn=978-1-35118-825-8|url=https://books.google.com/books?id=KE7ADwAAQBAJ&pg=PT261}}</ref>

====Oral====
Infections that are transmitted primarily by oral means may be caught through direct oral contact such as [[kiss]]ing, or by indirect contact such as by sharing a drinking glass or a cigarette. Infections that are known to be transmissible by kissing or by other direct or indirect oral contact include all of the infections transmissible by droplet contact and (at least) all forms of [[herpesviridae|herpes viruses]], namely [[Cytomegalovirus]] infections herpes simplex virus (especially HSV-1) and [[infectious mononucleosis]]. {{citation needed|date=September 2015}}

====Mother-to-child transmission====
[[File:Brocky, Karoly - Mother and Child (1846-50).jpg|thumb|Brocky, Karoly - Mother and Child (1846-50)]]
{{Main|Vertically transmitted disease}}
This is from mother to child (more rarely father to child), often ''in utero'', during [[childbirth]] (also referred to as [[perinatal infection]]) or during postnatal physical contact between parents and offspring. In mammals, including humans, it occurs also via [[breastfeeding|breast milk]] (transmammary transmission). [[Infectious disease]]s that can be transmitted in this way include: HIV, hepatitis B and syphilis. Many mutualistic organisms are transmitted vertically.<ref name="auto">{{cite journal| vauthors = Ebert D |date=2013|title=The Epidemiology and Evolution of Symbionts with Mixed-Mode Transmission|journal=Annual Review of Ecology, Evolution, and Systematics|volume=44|pages=623–643|doi=10.1146/annurev-ecolsys-032513-100555}}</ref>

====Iatrogenic====
Transmission [[iatrogenic|due to medical procedures]], such as touching a wound, the use of contaminated medical equipment, or an [[Injection (medicine)|injection]] or [[organ transplant|transplantation]] of infected material. Some diseases that can be transmitted [[iatrogenic]]ally include [[Creutzfeldt–Jakob disease]], [[HIV]], and many more.<ref>{{Cite web |date=2017-10-23 |title=Creutzfeldt-Jakob disease |url=https://www.nhs.uk/conditions/creutzfeldt-jakob-disease-cjd/ |access-date=2023-09-12 |website=nhs.uk |language=en}}</ref><ref>{{cite journal | vauthors = Rouet F, Nouhin J, Zheng DP, Roche B, Black A, Prak S, Leoz M, Gaudy-Graffin C, Ferradini L, Mom C, Mam S, Gautier C, Lesage G, Ken S, Phon K, Kerleguer A, Yang C, Killam W, Fujita M, Mean C, Fontenille D, Barin F, Plantier JC, Bedford T, Ramos A, Saphonn V | display-authors = 6 | title = Massive Iatrogenic Outbreak of Human Immunodeficiency Virus Type 1 in Rural Cambodia, 2014-2015 | journal = Clinical Infectious Diseases | volume = 66 | issue = 11 | pages = 1733–1741 | date = May 2018 | pmid = 29211835 | pmc = 5963970 | doi = 10.1093/cid/cix1071 }}</ref>

==== Needle sharing ====
This is the practice of intravenous drug-users by which a needle or [[syringe]] is shared by multiple individuals to administer [[intravenous drug]]s such as heroin, steroids, and hormones. This can act as a vector for [[blood-borne disease]]s, such as [[Hepatitis C]] (HCV) and [[HIV]].<ref>{{Cite web |date=2022-03-30 |title=HIV and Injection Drug Use {{!}} HIV Transmission {{!}} HIV Basics {{!}} HIV/AIDS {{!}} CDC |url=https://www.cdc.gov/hiv/basics/hiv-transmission/injection-drug-use.html |access-date=2023-09-12 |website=www.cdc.gov |language=en-us}}</ref>