Ebola

==Cause==
EVD in humans is caused by four of six viruses of the genus ''[[Ebolavirus]]''. The four are [[Bundibugyo virus]] (BDBV), [[Sudan virus]] (SUDV), [[Taï Forest virus]] (TAFV) and one simply called [[Ebola virus]] (EBOV, formerly Zaire Ebola virus).<ref name="Hoenen2012" /> EBOV, species ''[[Zaire ebolavirus]]'', is the most dangerous of the known EVD-causing viruses, and is responsible for the largest number of outbreaks.<ref name="KuhnArch">{{Cite journal |display-authors=6 |vauthors=Kuhn JH, Becker S, Ebihara H, Geisbert TW, Johnson KM, Kawaoka Y, Lipkin WI, Negredo AI, Netesov SV, Nichol ST, Palacios G, Peters CJ, Tenorio A, Volchkov VE, Jahrling PB |date=December 2010 |title=Proposal for a revised taxonomy of the family Filoviridae: Classification, names of taxa and viruses, and virus abbreviations |journal=Archives of Virology |volume=155 |issue=12 |pages=2083–2103 |doi=10.1007/s00705-010-0814-x |pmc=3074192 |pmid=21046175}}</ref> The fifth and sixth viruses, [[Reston virus]] (RESTV) and [[Bombali ebolavirus|Bombali virus]] (BOMV),<ref>{{Cite web | vauthors = Branswell H |date=27 July 2018 |title=New Ebola species is reported for first time in a decade |url=https://www.statnews.com/2018/07/27/ebola-virus-discovery/ |access-date=8 July 2022 |website=[[Stat (website)|Stat]] |language=en-US}}</ref> are not thought to cause disease in humans, but have caused disease in other primates.<ref name="Spickler">{{Cite web | vauthors = Spickler A |title=Ebolavirus and Marburgvirus Infections |url=http://www.cfsph.iastate.edu/Factsheets/pdfs/viral_hemorrhagic_fever_filovirus.pdf |url-status=live |archive-url=https://web.archive.org/web/20150430165458/http://www.cfsph.iastate.edu/Factsheets/pdfs/viral_hemorrhagic_fever_filovirus.pdf |archive-date=30 April 2015}}</ref><ref>{{Cite web |title=About Ebola Virus Disease |url=https://www.cdc.gov/vhf/ebola/about.html |url-status=live |archive-url=https://web.archive.org/web/20141016080233/https://www.cdc.gov/vhf/ebola/about.html |archive-date=16 October 2014 |access-date=18 October 2014 |publisher=[[Centers for Disease Control and Prevention]] (CDC)}}</ref> All five viruses are closely related to [[marburgvirus]]es.<ref name="Hoenen2012" />

===Virology===
{{Main|Ebolavirus|l1=''Ebolavirus'' (taxonomic group)|Ebola virus|l2=Ebola virus (specific virus)}}
[[File:Ebola virus virion.jpg|thumb|[[Electron micrograph]] of an Ebola virus [[virion]]]]

Ebolaviruses contain single-stranded, non-infectious [[RNA]] [[genome]]s.<ref name="Fauquet2005">{{Cite book | vauthors = Pringle CR |title=Virus Taxonomy – Eighth Report of the International Committee on Taxonomy of Viruses |publisher=Elsevier/Academic Press |year=2005 |isbn=978-0-12-370200-5 | veditors = Fauquet CM, Mayo MA, Maniloff J, Desselberger U, Ball LA  |location=San Diego |pages=609–614 |chapter=Order Mononegavirales }}</ref> ''Ebolavirus'' genomes contain seven [[gene]]s including [[Three prime untranslated region|3'-UTR]]-''NP''-''VP35''-''VP40''-''GP''-''VP30''-''VP24''-''L''-[[Five prime untranslated region|5'-UTR]].<ref name="Feldmann2011" /><ref name="Stahelin2014">{{Cite journal |vauthors=Stahelin RV |date=June 2014 |title=Membrane binding and bending in Ebola VP40 assembly and egress |journal=Front Microbiol |volume=5 |page=300 |doi=10.3389/fmicb.2014.00300 |pmc=4061899 |pmid=24995005 |doi-access=free}}</ref> The genomes of the five different ebolaviruses (BDBV, EBOV, RESTV, SUDV and TAFV) differ in [[nucleic acid sequence|sequence]] and the number and location of gene overlaps. As with all [[filovirus]]es, ebolavirus virions are filamentous particles that may appear in the shape of a shepherd's crook, of a "U" or of a "6," and they may be coiled, toroid or branched.<ref name="Stahelin2014" /><ref>{{Cite journal |display-authors=6 |vauthors=Ascenzi P, Bocedi A, Heptonstall J, Capobianchi MR, Di Caro A, Mastrangelo E, Bolognesi M, Ippolito G |date=June 2008 |title=Ebolavirus and Marburgvirus: insight the Filoviridae family |url=https://air.unimi.it/retrieve/handle/2434/53604/1077822/Ebola_2008%29_Proofs.pdf |journal=Mol Aspects Med |volume=29 |issue=3 |pages=151–185 |doi=10.1016/j.mam.2007.09.005 |pmid=18063023 |hdl-access=free |hdl=2434/53604}}</ref> In general, ebolavirions are 80 nanometers (nm) in width and may be as long as 14,000&nbsp;nm.<ref name="Chippaux2014">{{Cite journal |vauthors=Chippaux JP |date=October 2014 |title=Outbreaks of Ebola virus disease in Africa: the beginnings of a tragic saga |journal=J Venom Anim Toxins Incl Trop Dis |volume=20 |issue=1 |page=44 |doi=10.1186/1678-9199-20-44 |pmc=4197285 |pmid=25320574 |doi-access=free }}</ref>

Their [[Biological life cycle|life cycle]] is thought to begin with a virion attaching to specific [[Cell surface receptor|cell-surface receptors]] such as [[C-type lectin]]s, [[DC-SIGN]], or [[integrin]]s, which is followed by fusion of the [[Pinocytosis|viral envelope with cellular membranes]].<ref name="Misasi2014">{{Cite journal |vauthors=Misasi J, Sullivan NJ |date=October 2014 |title=Camouflage and Misdirection: The Full-On Assault of Ebola Virus Disease |journal=Cell |volume=159 |issue=3 |pages=477–486 |doi=10.1016/j.cell.2014.10.006 |pmc=4243531 |pmid=25417101}}</ref> The virions taken up by the cell then travel to acidic [[endosome]]s and [[lysosome]]s where the viral envelope glycoprotein GP is cleaved.<ref name="Misasi2014" /> This processing appears to allow the virus to bind to cellular proteins enabling it to fuse with internal cellular membranes and release the viral [[nucleocapsid]].<ref name="Misasi2014" /> The ''Ebolavirus'' structural glycoprotein (known as GP1,2) is responsible for the virus' ability to bind to and infect targeted cells.<ref name="Kuhl2012">{{Cite journal |vauthors=Kühl A, Pöhlmann S |date=September 2012 |title=How Ebola virus counters the interferon system |journal=Zoonoses Public Health |volume=59 |issue=Supplement 2 |pages=116–131 |doi=10.1111/j.1863-2378.2012.01454.x |pmc=7165950 |pmid=22958256}}</ref> The viral [[RNA-dependent RNA polymerase|RNA polymerase]], encoded by the ''L'' gene, partially uncoats the nucleocapsid and [[Transcription (genetics)|transcribes]] the genes into positive-strand [[mRNA]]s, which are then [[translation (biology)|translated]] into structural and nonstructural proteins. The most abundant protein produced is the nucleoprotein, whose concentration in the host cell determines when L switches from gene transcription to genome replication. Replication of the viral genome results in full-length, positive-strand antigenomes that are, in turn, transcribed into genome copies of negative-strand virus progeny.<ref name="Olejnik2011" /> Newly synthesised structural proteins and genomes self-assemble and accumulate near the inside of the [[cell membrane]]. Virions [[Budding|bud]] off from the cell, gaining their envelopes from the cellular membrane from which they bud. The mature progeny particles then infect other cells to repeat the cycle. The genetics of the Ebola virus are difficult to study because of EBOV's virulent characteristics.<ref name="Feldmann2005">{{Cite book | vauthors = Feldmann H, Geisbert TW, Jahrling PB, Klenk H, Netesov SV, Peters CJ, Sanchez A, Swanepoel R, Volchkov VE |title=Virus Taxonomy – Eighth Report of the International Committee on Taxonomy of Viruses | publisher=Elsevier/Academic Press |year=2005 |isbn=978-0123702005 | veditors = Fauquet CM, Mayo MA, Maniloff J, Desselberger U, Ball LA  }}</ref>

===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]]
<!-- Between people -->
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>

<!-- Dead bodies -->
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" />

===Initial case===
<!-- Animals to humans -->
[[File:Bushmeat - Buschfleisch Ghana.JPG|thumb|[[Bushmeat]] having been smoked in [[Ghana]]. In Africa, wild animals including fruit bats are hunted for food and are referred to as bushmeat.<ref name="CDC2014Bush">{{Cite web |date=12 October 2014 |title=Risk of Exposure |url=https://www.cdc.gov/vhf/ebola/exposure/index.html |url-status=live |archive-url=https://web.archive.org/web/20141016205158/https://www.cdc.gov/vhf/ebola/exposure/index.html |archive-date=16 October 2014 |access-date=18 October 2014 |publisher=[[Centers for Disease Control and Prevention]] (CDC)}}</ref><ref>{{Cite web |date=21 July 2014 |title=FAO warns of fruit bat risk in West African Ebola epidemic |url=http://www.fao.org/news/story/en/item/239123/icode/ |url-status=live |archive-url=https://web.archive.org/web/20141013151812/http://www.fao.org/news/story/en/item/239123/icode/ |archive-date=13 October 2014 |access-date=22 October 2014 |website=fao.org}}</ref> In equatorial Africa, human consumption of bushmeat has been linked to animal-to-human transmission of diseases, including Ebola.<ref name="urlAfrican monkey meat that could be behind the next HIV – Health News – Health & Families – The Independent">{{Cite news | vauthors = Williams E |title=African monkey meat that could be behind the next HIV |work=[[The Independent]] |url=https://www.independent.co.uk/life-style/health-and-families/health-news/african-monkey-meat-that-could-be-behind-the-next-hiv-7786152.html |url-status=live |archive-url=https://web.archive.org/web/20170622133307/http://www.independent.co.uk/life-style/health-and-families/health-news/african-monkey-meat-that-could-be-behind-the-next-hiv-7786152.html |archive-date=22 June 2017 |quote=25 people in Bakaklion, Cameroon killed due to eating of ape }}</ref>]]

Although it is not entirely clear how Ebola initially spreads from animals to humans, the spread is believed to involve direct contact with an infected wild animal or fruit bat.<ref name=CDC2014T/> Besides bats, other wild animals that are sometimes infected with EBOV include several species of monkeys such as [[baboon]]s, [[great apes]] ([[chimpanzee]]s and [[gorilla]]s), and [[duikers]] (a species of [[antelope]]).<ref name="urlEbolavirus – Pathogen Safety Data Sheets">{{Cite web |date=17 September 2001 |title=Ebolavirus – Pathogen Safety Data Sheets |url=http://www.phac-aspc.gc.ca/lab-bio/res/psds-ftss/ebola-eng.php |url-status=live |archive-url=https://web.archive.org/web/20140820211755/http://www.phac-aspc.gc.ca/lab-bio/res/psds-ftss/ebola-eng.php |archive-date=20 August 2014 |access-date=22 August 2014 |publisher=Public Health Agency of Canada }}</ref>

Animals may become infected when they eat fruit partially eaten by bats carrying the virus.<ref name=Gon2007/> Fruit production, animal behavior and other factors may trigger outbreaks among animal populations.<ref name="Gon2007">{{Cite book |title=Wildlife and Emerging Zoonotic Diseases: The Biology, Circumstances and Consequences of Cross-Species Transmission |vauthors=Gonzalez JP, Pourrut X, Leroy E |work=Current Topics in Microbiology and Immunology |year=2007 |isbn=978-3540709619 |series=Ebolavirus and other filoviruses |volume=315 |pages=363–387 |chapter=Ebolavirus and Other Filoviruses |doi=10.1007/978-3-540-70962-6_15 |pmc=7121322 |pmid=17848072}}</ref>

Evidence indicates that both domestic dogs and pigs can also be infected with EBOV.<ref name="Weingartl_2013">{{Cite book |title=Vaccines and Diagnostics for Transboundary Animal Diseases |vauthors=Weingartl HM, Nfon C, Kobinger G |chapter=Review of Ebola Virus Infections in Domestic Animals |date=May 2013 |work=Dev Biol |isbn=978-3318023657 |series=Developments in Biologicals |volume=135 |pages=211–218 |doi=10.1159/000178495 |pmid=23689899 |author-link3=Gary Kobinger}}</ref> Dogs do not appear to develop symptoms when they carry the virus, and pigs appear to be able to transmit the virus to at least some primates.<ref name="Weingartl_2013" /> Although some dogs in an area in which a human outbreak occurred had antibodies to EBOV, it is unclear whether they played a role in spreading the disease to people.<ref name="Weingartl_2013" />

===Reservoir===
The [[natural reservoir]] for Ebola has yet to be confirmed; however, [[bat]]s are considered to be the most likely candidate.<ref name="Chowell2014">{{Cite journal |vauthors=Chowell G, Nishiura H |date=October 2014 |title=Transmission dynamics and control of Ebola virus disease (EVD): a review |journal=BMC Med |volume=12 |issue=1 |page=196 |doi=10.1186/s12916-014-0196-0 |pmc=4207625 |pmid=25300956 |doi-access=free }}</ref> Three types of fruit bats (''[[Hypsignathus monstrosus]]'', ''[[Epomops franqueti]]'' and ''[[Myonycteris torquata]]'') were found to possibly carry the virus without getting sick.<ref>{{Cite journal |vauthors=Laupland KB, Valiquette L |date=May 2014 |title=Ebola virus disease |journal=Can J Infect Dis Med Microbiol |volume=25 |issue=3 |pages=128–129 |doi=10.1155/2014/527378 |pmc=4173971 |pmid=25285105 |doi-access=free}}</ref> {{As of|2013}}, whether other animals are involved in its spread is not known.<ref name="Weingartl_2013" /> Plants, [[arthropod]]s, [[rodent]]s, and birds have also been considered possible viral reservoirs.<ref name=WHO2014/><ref name="Sharma2015" />

Bats were known to roost in the cotton factory in which the [[index case|first case]]s of the 1976 and 1979 outbreaks were observed, and they have also been implicated in Marburg virus infections in 1975 and 1980.<ref name="Pourrut2005" /> Of 24&nbsp;plant and 19&nbsp;vertebrate species experimentally inoculated with EBOV, only bats became infected.<ref>{{Cite journal |display-authors=6 |vauthors=Swanepoel R, Leman PA, Burt FJ, Zachariades NA, Braack LE, Ksiazek TG, Rollin PE, Zaki SR, Peters CJ |date=October 1996 |title=Experimental inoculation of plants and animals with Ebola virus |journal=Emerg. Infect. Dis. |volume=2 |issue=4 |pages=321–325 |doi=10.3201/eid0204.960407 |issn=1080-6040 |pmc=2639914 |pmid=8969248}}</ref> The bats displayed no clinical signs of disease, which is considered evidence that these bats are a reservoir species of EBOV. In a 2002–2003 survey of 1,030&nbsp;animals including 679&nbsp;bats from [[Gabon]] and the [[Republic of the Congo]], immunoglobulin G (IgG) immune defense molecules indicative of Ebola infection were found in three bat species; at various periods of study, between 2.2 and 22.6% of bats were found to contain both RNA sequences and IgG molecules indicating Ebola infection.<ref>{{Cite journal |display-authors=6 |vauthors=Leroy EM, Kumulungui B, Pourrut X, Rouquet P, Hassanin A, Yaba P, Délicat A, Paweska JT, Gonzalez JP, Swanepoel R |date=December 2005 |title=Fruit bats as reservoirs of Ebola virus |journal=Nature |volume=438 |issue=7068 |pages=575–576 |bibcode=2005Natur.438..575L |doi=10.1038/438575a |pmid=16319873 |s2cid=4403209}}</ref> Antibodies against Zaire and Reston viruses have been found in fruit bats in [[Bangladesh]], suggesting that these bats are also potential hosts of the virus and that the filoviruses are present in Asia.<ref name="Olival2013">{{Cite journal |display-authors=6 |vauthors=Olival KJ, Islam A, Yu M, Anthony SJ, Epstein JH, Khan SA, Khan SU, Crameri G, Wang LF, Lipkin WI, Luby SP, Daszak P |date=February 2013 |title=Ebola virus antibodies in fruit bats, Bangladesh |journal=Emerg. Infect. Dis. |volume=19 |issue=2 |pages=270–273 |doi=10.3201/eid1902.120524 |pmc=3559038 |pmid=23343532}}</ref>

Between 1976 and 1998, in 30,000&nbsp;mammals, birds, reptiles, amphibians and [[arthropod]]s sampled from regions of EBOV outbreaks, no Ebola virus was detected apart from some genetic traces found in six rodents (belonging to the species ''[[Mus setulosus]]'' and ''[[Praomys]]'') and one [[shrew]] (''[[Sylvisorex ollula]]'') collected from the [[Central African Republic]].<ref name="Pourrut2005">{{Cite journal |display-authors=6 |vauthors=Pourrut X, Kumulungui B, Wittmann T, Moussavou G, Délicat A, Yaba P, Nkoghe D, Gonzalez JP, Leroy EM |date=June 2005 |title=The natural history of Ebola virus in Africa |journal=Microbes Infect |volume=7 |issue=7–8 |pages=1005–1014 |doi=10.1016/j.micinf.2005.04.006 |pmid=16002313|doi-access=free }}</ref><ref name="Morvan1999">{{Cite journal |display-authors=6 |vauthors=Morvan JM, Deubel V, Gounon P, Nakouné E, Barrière P, Murri S, Perpète O, Selekon B, Coudrier D, Gautier-Hion A, Colyn M, Volehkov V |date=December 1999 |title=Identification of Ebola virus sequences present as RNA or DNA in organs of terrestrial small mammals of the Central African Republic |journal=Microbes and Infection |volume=1 |issue=14 |pages=1193–1201 |doi=10.1016/S1286-4579(99)00242-7 |pmid=10580275}}</ref> However, further research efforts have not confirmed rodents as a reservoir.<ref name="Groseth2007">{{Cite journal |vauthors=Groseth A, Feldmann H, Strong JE |date=September 2007 |title=The ecology of Ebola virus |journal=Trends Microbiol |volume=15 |issue=9 |pages=408–416 |doi=10.1016/j.tim.2007.08.001 |pmid=17698361}}</ref> Traces of EBOV were detected in the carcasses of gorillas and chimpanzees during outbreaks in 2001 and 2003, which later became the source of human infections. However, the high rates of death in these species resulting from EBOV infection make it unlikely that these species represent a natural reservoir for the virus.<ref name="Pourrut2005" />

[[Deforestation in the Democratic Republic of the Congo|Deforestation]] has been mentioned as a possible contributor to recent outbreaks, including the [[West African Ebola virus epidemic]]. Index cases of EVD have often been close to recently deforested lands.<ref>{{Cite web |date=10 April 2018 |title=Did deforestation cause the Ebola outbreak? |url=https://newint.org/features/web-exclusive/2018/04/10/deforestation-ebola-outbreak |access-date=10 July 2018 |website=New Internationalist}}</ref><ref>{{Cite journal |display-authors=6 |vauthors=Olivero J, Fa JE, Real R, Márquez AL, Farfán MA, Vargas JM, Gaveau D, Salim MA, Park D, Suter J, King S, Leendertz SA, Sheil D, Nasi R |date=30 October 2017 |title=Recent loss of closed forests is associated with Ebola virus disease outbreaks |journal=Scientific Reports |volume=7 |issue=1 |pages=14291 |bibcode=2017NatSR...714291O |doi=10.1038/s41598-017-14727-9 |issn=2045-2322 |pmc=5662765 |pmid=29085050}}</ref>