Ebola

===Transmission===
[[File:EbolaCycle.png|thumb|upright=1.8|Life cycles of the ''[[Ebolavirus]]'']]
[[File:Ebola illustration- safe burial (15573264517).jpg|thumb|An illustration of safe burial practices]]
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It is believed that between people, Ebola disease spreads only by direct contact with the blood or other [[body fluid]]s of a person who has developed symptoms of the disease.<ref name="Funk2014" /><ref>{{Cite web |date=5 November 2014 |title=Ebola (Ebola Virus Disease) Transmission |url=https://www.cdc.gov/vhf/ebola/transmission/index.html |url-status=live |archive-url=https://web.archive.org/web/20141106022141/https://www.cdc.gov/vhf/ebola/transmission/index.html |archive-date=6 November 2014 |access-date=7 November 2014 |publisher=[[Centers for Disease Control and Prevention]] (CDC)}}</ref><ref name="Drazen2014">{{Cite journal |vauthors=Drazen JM, Kanapathipillai R, Campion EW, Rubin EJ, Hammer SM, Morrissey S, Baden LR |date=November 2014 |title=Ebola and quarantine |journal=N Engl J Med |volume=371 |issue=21 |pages=2029–2030 |doi=10.1056/NEJMe1413139 |pmid=25347231|doi-access=free }}</ref> Body fluids that may contain Ebola viruses include saliva, mucus, vomit, feces, sweat, tears, breast milk, urine and [[semen]].<ref name=cdc9months/><ref name=CDC2014QAT/> The WHO states that only people who are very sick are able to spread Ebola disease in [[saliva]], and the virus has not been reported to be transmitted through sweat. Most people spread the virus through blood, [[feces]] and vomit.<ref>{{Cite news | vauthors = McNeil Jr DG |author-link=Donald McNeil Jr. |name-list-style=vanc |date=3 October 2014 |title=Ask Well: How Does Ebola Spread? How Long Can the Virus Survive? |work=[[The New York Times]] |url=http://well.blogs.nytimes.com/2014/10/03/ebola-ask-well-spread-public-transit/ |url-status=live |access-date=24 October 2014 |archive-url=https://web.archive.org/web/20141024061521/http://well.blogs.nytimes.com/2014/10/03/ebola-ask-well-spread-public-transit/ |archive-date=24 October 2014 }}</ref> Entry points for the virus include the nose, mouth, eyes, open wounds, cuts and abrasions.<ref name="CDC2014QAT">{{Cite web |date=September 2014 |title=Q&A on Transmission, Ebola |url=https://www.cdc.gov/vhf/ebola/transmission/qas.html |url-status=live |archive-url=https://web.archive.org/web/20141002210702/https://www.cdc.gov/vhf/ebola/transmission/qas.html |archive-date=2 October 2014 |access-date=3 October 2014 |publisher=[[Centers for Disease Control and Prevention]] (CDC)}}</ref> Ebola may be spread through large [[Transmission (medicine)#Droplet|droplets]]; however, this is believed to occur only when a person is very sick.<ref name="CDCNOV2014">{{Cite web |date=1 November 2014 |title=How Ebola Is Spread |url=https://www.cdc.gov/vhf/ebola/pdf/infections-spread-by-air-or-droplets.pdf |url-status=live |archive-url=https://web.archive.org/web/20170708092027/https://www.cdc.gov/vhf/ebola/pdf/infections-spread-by-air-or-droplets.pdf |archive-date=8 July 2017 |publisher=[[Centers for Disease Control and Prevention]] (CDC)}}</ref> This contamination can happen if a person is splashed with droplets.<ref name=CDCNOV2014/> Contact with surfaces or objects contaminated by the virus, particularly needles and syringes, may also transmit the infection.<ref name=CDC2014T/><ref name="Chowell2014" /> The virus is able to survive on objects for a few hours in a dried state, and can survive for a few days within body fluids outside of a person.<ref name=CDC2014QAT/><ref name=Ost2015/>

The Ebola virus may be able to persist for more than three months in the semen after recovery, which could lead to infections via [[sexual intercourse]].<ref name=cdc9months/><ref>{{Cite web |date=4 April 2015 |title=Sexual transmission of the Ebola Virus : evidence and knowledge gaps |url=https://www.who.int/reproductivehealth/topics/rtis/ebola-virus-semen/en/ |url-status=live |archive-url=https://web.archive.org/web/20150414084657/https://www.who.int/reproductivehealth/topics/rtis/ebola-virus-semen/en/ |archive-date=14 April 2015 |access-date=16 April 2015 |publisher=[[World Health Organization]] (WHO)}}</ref><ref>{{Cite news | vauthors = Wu B |date=2 May 2015 |title=Ebola Can Be Transmitted Through Sex |work=Science Times |url=http://www.sciencetimes.com/articles/6000/20150502/ebola-transmitted-through-sex.htm |url-status=live |access-date=3 May 2015 |archive-url=https://web.archive.org/web/20150502222419/http://www.sciencetimes.com/articles/6000/20150502/ebola-transmitted-through-sex.htm |archive-date=2 May 2015}}</ref> Virus persistence in semen for over a year has been recorded in a national screening programme.<ref>{{Cite journal |display-authors=6 |vauthors=Soka MJ, Choi MJ, Baller A, White S, Rogers E, Purpura LJ, Mahmoud N, Wasunna C, Massaquoi M, Abad N, Kollie J, Dweh S, Bemah PK, Christie A, Ladele V, Subah OC, Pillai S, Mugisha M, Kpaka J, Kowalewski S, German E, Stenger M, Nichol S, Ströher U, Vanderende KE, Zarecki SM, Green HH, Bailey JA, Rollin P, Marston B, Nyenswah TG, Gasasira A, Knust B, Williams D |year=2016 |title=Prevention of sexual transmission of Ebola in Liberia through a national semen testing and counselling programme for survivors: an analysis of Ebola virus RNA results and behavioural data |journal=Lancet Global Health |volume=4 |issue=10 |pages=e736–e743 |doi=10.1016/S2214-109X(16)30175-9 |pmid=27596037 |doi-access=free}}</ref> Ebola may also occur in the breast milk of women after recovery, and it is not known when it is safe to breastfeed again.<ref name=CDCBreast2014/> The virus was also found in the eye of one patient in 2014, two months after it was cleared from his blood.<ref>{{Cite journal |display-authors=6 |vauthors=Varkey JB, Shantha JG, Crozier I, Kraft CS, Lyon GM, Mehta AK, Kumar G, Smith JR, Kainulainen MH, Whitmer S, Ströher U, Uyeki TM, Ribner BS, Yeh S |date=7 May 2015 |title=Persistence of Ebola Virus in Ocular Fluid during Convalescence |journal=The New England Journal of Medicine |volume=372 |issue=25 |pages=2423–227 |doi=10.1056/NEJMoa1500306 |pmc=4547451 |pmid=25950269 |hdl=2328/35704}}</ref> Otherwise, people who have recovered are not infectious.<ref name=CDC2014T/>

The potential for [[pandemics|widespread infections]] in countries with medical systems capable of observing correct medical isolation procedures is considered low.<ref name="CDCPress2014">{{Cite web |date=28 July 2014 |title=CDC Telebriefing on Ebola outbreak in West Africa |url=https://www.cdc.gov/media/releases/2014/t0728-ebola.html |url-status=live |archive-url=https://web.archive.org/web/20140802025607/https://www.cdc.gov/media/releases/2014/t0728-ebola.html |archive-date=2 August 2014 |access-date=3 August 2014 |publisher=[[Centers for Disease Control and Prevention]] (CDC)}}</ref> Usually when someone has symptoms of the disease, they are unable to travel without assistance.<ref name="WHO2014T">{{Cite web |date=14 August 2014 |title=Air travel is low-risk for Ebola transmission |url=https://www.who.int/mediacentre/news/notes/2014/ebola-travel/en/ |url-status=dead |archive-url=https://web.archive.org/web/20150119231747/https://www.who.int/mediacentre/news/notes/2014/ebola-travel/en/ |archive-date=19 January 2015 |publisher=[[World Health Organization]] (WHO)}}</ref>

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Dead bodies remain infectious; thus, people handling human remains in practices such as traditional burial rituals or more modern processes such as [[embalming]] are at risk.<ref name=CDCPress2014/> Of the cases of Ebola infections in Guinea during the 2014 outbreak, 69% are believed to have been contracted via unprotected (or unsuitably protected) contact with infected corpses during certain Guinean burial rituals.<ref name="Chan2014">{{Cite journal |vauthors=Chan M |date=September 2014 |title=Ebola virus disease in West Africa – no early end to the outbreak |journal=N Engl J Med |volume=371 |issue=13 |pages=1183–1185 |doi=10.1056/NEJMp1409859 |pmid=25140856|doi-access=free }}</ref><ref>{{Cite web |title=Sierra Leone: a traditional healer and a funeral |url=https://www.who.int/csr/disease/ebola/ebola-6-months/sierra-leone/en/ |url-status=dead |archive-url=https://web.archive.org/web/20141006082559/https://www.who.int/csr/disease/ebola/ebola-6-months/sierra-leone/en/ |archive-date=6 October 2014 |access-date=6 October 2014 |publisher=[[World Health Organization]] (WHO) }}</ref>

<!-- Hospitals -->
Health-care workers treating people with Ebola are at greatest risk of infection.<ref name="CDC2014T">{{Cite web |date=17 October 2014 |title=Transmission |url=https://www.cdc.gov/vhf/ebola/transmission/ |url-status=live |archive-url=https://web.archive.org/web/20141019024316/https://www.cdc.gov/vhf/ebola/transmission/ |archive-date=19 October 2014 |access-date=18 October 2014 |publisher=[[Centers for Disease Control and Prevention]] (CDC)}}</ref> The risk increases when they do not have appropriate protective clothing such as masks, gowns, gloves and eye protection; do not wear it properly; or handle contaminated clothing incorrectly.<ref name=CDC2014T/> This risk is particularly common in parts of Africa where the disease mostly occurs and health systems function poorly.<ref>{{Cite web | vauthors = Salaam-Blyther T |date=26 August 2014 |title=The 2014 Ebola Outbreak: International and U.S. Responses |url=https://fas.org/sgp/crs/row/R43697.pdf |url-status=live |archive-url=https://web.archive.org/web/20140903122230/http://fas.org/sgp/crs/row/R43697.pdf |archive-date=3 September 2014 |access-date=9 September 2014}}</ref> There has been transmission [[nosocomial|in hospitals]] in some African countries that reuse hypodermic needles.<ref>{{Cite book |url=https://books.google.com/books?id=fsaWlKQ4OjcC&pg=PA141 |title=Emerging infectious diseases trends and issues |date=2007 |publisher=Springer |isbn=978-0826103505 | veditors = Lashley FR, Durham JD |edition=2nd |location=New York |page=141 |archive-url=https://web.archive.org/web/20160509224252/https://books.google.com/books?id=fsaWlKQ4OjcC&pg=PA141 |archive-date=9 May 2016 |url-status=live}}</ref><ref>{{Cite book |url=https://books.google.com/books?id=x15umovaD08C&pg=PA170 |title=Hunter's tropical medicine and emerging infectious disease |publisher=Elsevier |year=2013 |isbn=978-1455740437 | veditors = Magill AJ, Strickland GT, Maguire JH, Ryan ET, Solomon T |edition=9th |location=London; New York |pages=170–172 |oclc=822525408  |archive-url=https://web.archive.org/web/20160520120141/https://books.google.com/books?id=x15umovaD08C&pg=PA170 |archive-date=20 May 2016 |url-status=live}}</ref> Some health-care centres caring for people with the disease do not have running water.<ref name="CDCQA2014">{{Cite web |date=22 May 2018 |title=Questions and Answers on Ebola Hemorrhagic Fever |url=https://www.cdc.gov/vhf/ebola/outbreaks/guinea/qa.html |url-status=live |archive-url=https://web.archive.org/web/20170728032458/https://www.cdc.gov/vhf/ebola/outbreaks/guinea/qa.html |archive-date=28 July 2017 |publisher=[[Centers for Disease Control and Prevention]] (CDC)}}</ref> In the United States the spread to two medical workers treating infected patients prompted criticism of inadequate training and procedures.<ref name="NBC-ebolaTX">{{Cite web |date=15 October 2014 |title=Ebola in Texas: Second Health Care Worker Tests Positive |url=https://www.nbcnews.com/storyline/ebola-virus-outbreak/ebola-texas-second-health-care-worker-tests-positive-n226161 |url-status=live |archive-url=https://web.archive.org/web/20141015211852/http://www.nbcnews.com/storyline/ebola-virus-outbreak/ebola-texas-second-health-care-worker-tests-positive-n226161 |archive-date=15 October 2014 |website=NBC News}}</ref>

<!-- Air, water, insects -->
Human-to-human transmission of EBOV through the air has not been reported to occur during EVD outbreaks,<ref name=WHOAir2014/> and airborne transmission has only been demonstrated in very strict laboratory conditions, and then only from pigs to [[primates]], but not from primates to primates.<ref name="Funk2014" /><ref name="Chowell2014" /> Spread of EBOV by water, or food other than bushmeat, has not been observed.<ref name=CDC2014T/><ref name="Chowell2014" /> No spread by mosquitos or other insects has been reported.<ref name=CDC2014T/> Other possible methods of transmission are being studied.<ref name="Ost2015">{{Cite journal |display-authors=6 |vauthors=Osterholm MT, Moore KA, Kelley NS, Brosseau LM, Wong G, Murphy FA, Peters CJ, LeDuc JW, Russell PK, Van Herp M, Kapetshi J, Muyembe JJ, Ilunga BK, Strong JE, Grolla A, Wolz A, Kargbo B, Kargbo DK, Sanders DA, Kobinger GP |date=19 February 2015 |title=Transmission of Ebola viruses: what we know and what we do not know |journal=mBio |volume=6 |issue=2 |pages=e00137 |doi=10.1128/mBio.00137-15 |pmc=4358015 |pmid=25698835}}</ref>

Airborne transmission among humans is theoretically possible due to the presence of Ebola virus particles in saliva, which can be discharged into the air with a cough or sneeze, but observational data from previous epidemics suggests the actual risk of airborne transmission is low.<ref name="Jones2015">{{Cite journal |vauthors=Jones RM, Brosseau LM |date=May 2015 |title=Aerosol transmission of infectious disease |journal=Journal of Occupational and Environmental Medicine |type=Review |volume=57 |issue=5 |pages=501–508 |doi=10.1097/JOM.0000000000000448 |pmid=25816216 |s2cid=11166016}}</ref> A number of studies examining airborne transmission broadly concluded that transmission from pigs to primates could happen without direct contact because, unlike humans and primates, pigs with EVD get very high ebolavirus concentrations in their lungs, and not their bloodstream.<ref name="virology1">{{Cite web |date=27 September 2014 |title=Transmission of Ebola virus |url=http://www.virology.ws/2014/09/27/transmission-of-ebola-virus/ |url-status=live |archive-url=https://web.archive.org/web/20160129111738/http://www.virology.ws/2014/09/27/transmission-of-ebola-virus/ |archive-date=29 January 2016 |access-date=22 January 2016 |website=virology.ws}}</ref> Therefore, pigs with EVD can spread the disease through droplets in the air or on the ground when they sneeze or cough.<ref name="sb1">{{Cite journal |vauthors=Weingartl HM, Embury-Hyatt C, Nfon C, Leung A, Smith G, Kobinger G |date=2012 |title=Transmission of Ebola virus from pigs to non-human primates |journal=Scientific Reports |volume=2 |page=811 |bibcode=2012NatSR...2E.811W |doi=10.1038/srep00811 |pmc=3498927 |pmid=23155478}}</ref> By contrast, humans and other primates accumulate the virus throughout their body and specifically in their blood, but not very much in their lungs.<ref name="sb1" /> It is believed that this is the reason researchers have observed pig to primate transmission without physical contact, but no evidence has been found of primates being infected without actual contact, even in experiments where infected and uninfected primates shared the same air.<ref name="virology1" /><ref name="sb1" />