Ebola virus disease

1. Ebola Virus Disease
EbolaVirusDisease (EVD) Also Ebolahemorrhagicfever(EHF). Ebolavirusdisease(EVD),isa
severe,oftenfatal illnessinhumans.The virusistransmittedtopeople fromwildanimalsand
spreadsinthe humanpopulationthrough human-to-humantransmission.The average EVDcase
fatalityrate isaround50% (WHO | Ebolavirusdisease).Itisone of the type of Filoviruses.
History of Ebola Virus
African Ebola Virus
Ebolaviruswas firstisolatedduringa1976 epidemicof severe hemorrhagicfeverinZaire andSudanand
namedfora riverinthe region.Duringthisepidemic,the more than600 casesresultedin430 deaths
and asymptomaticinfectionappearedtobe rare.One case of Ebola occurredin1977, and in1979 there
were 34 cases with22 deathsinthe Sudan. Afterthis,Eboladisease inAfricadisappeareduntil1994. In
late 1994, a Swissethologistworkinginthe IvoryCoastperformednecropsiesonchimps. Then,inMay
1995, there wasan epidemicinKikwit,Zaire,thatresultedin atleast315 caseswith>75% mortality.This
was followedbyseveral deathsinwesternAfricathatresultedfromconsumptionof amonkeythathad
diedof Ebola.Thenthere wasa prolongedseriesof smalleroutbreaksinGabonfrom1995 through
1997. In2000, Ebola appearedinUgandafor the firsttime andcaused an epidemicof more than425
cases.There have beenfurtheroutbreaksin2002, 2003, 2004, and 2005 invariouscountriesincluding
Gabon,the DemocraticRepublicof Congo,andSudan. A map showingthese variousfiloviral outbreaksis
showninFig.

2. Strains of Ebola virus
Three strainsor speciesof AfricanEbolavirusesare now recognizedwhichdifferintheirvirulence.
 Zaire ebolavirusisthe mostvirulentwithacase fatalityrate approaching90%.
 Sudanebolavirusislessvirulent.
 IvoryCoast ebolavirusisthe leastvirulent.
Reston Ebola Virus
A fourthstrainof Ebolavirusoriginatingfromthe Philippines(or,perhaps,anotherregionof
Asia) firstappearedasthe causative agentof an epidemicof hemorrhagicfeverinmonkeys
importedfromthe Philippines.ThisepidemicoccurredinReston,Virginia,nearWashington,
D.C.,in 1989. The deathswere atfirstattributedtosimianhemorrhagicfevervirus(SHFV),but
investigationbythe U.S.ArmyMedical ResearchInstitute forInfectiousDiseasesandthe
CentersforDisease Control andPreventionfoundthatbothSHFV andEbolaviruswere present
inthe monkeys.Believingthatthe communitywasatrisk forEbola,made eventhe more
alarmingbecause the epidemicwasoccurringinthe neighborhoodof the central governmentof
the UnitedStates,the army teamquicklydecidedtoeuthanize the monkeysanddecontaminate
the facility.Follow-upstudiesshowedthatfouranimal handlersatthe facilityhadbeeninfected
by the virusbuthad sufferednoillness.Thusthe strainof Ebolapresentinthe Restonmonkeys,

3. calledRestonebolavirus,seemstobe nonpathogenicforhumansalthoughitremains
pathogenicformonkeys.
Are Filoviruses a Major Threat?
To date,the filoviruseshave causedonlyalimitednumberof humaninfections.However,if a
filoviruswereto adaptto humanssuch that human-to-humantransmissionoccurredreadily,it
couldbecome a majorproblem.The probabilityof suchan eventisunknown
WHO – Key Facts of Ebola
• Ebolavirusdisease (EVD),formerlyknownasEbolahaemorrhagicfever,isasevere,often
fatal illnessinhumans.•The virusistransmittedtopeople fromwildanimalsandspreadsin
the humanpopulationthroughhuman-to-humantransmission.
• The average EVD case fatalityrate is around50%. Case fatalityrateshave variedfrom25%
to 90% inpast outbreaks.•The firstEVD outbreaksoccurredinremote villagesinCentral
Africa,neartropical rainforests,butthe mostrecentoutbreakinWestAfricahasinvolved
majorurban as well asrural areas.
• Communityengagementiskeyto successfullycontrollingoutbreaks.Goodoutbreakcontrol
reliesonapplyingapackage of interventions,namelycase management,surveillance and
contact tracing,a goodlaboratoryservice,safe burialsandsocial mobilization.
• Earlysupportive care withrehydration,symptomatictreatmentimprovessurvival.There is
as yetno licensedtreatmentproventoneutralize the virusbutarange of blood,
immunological anddrugtherapiesare underdevelopment.•There are currentlynolicensed
Ebolavaccinesbut 2 potential candidatesare undergoingevaluation
Signs & Symptoms
• Humansare notinfectiousuntil theydevelopsymptoms.
• Firstsymptomsare the suddenonsetof feverfatigue,muscle pain,headache andsore
throat.

4. • Thisisfollowedbyvomiting,diarrhea,rash,symptomsof impairedkidneyandliverfunction,
and insome cases,bothinternal andexternal bleeding
• Laboratoryfindingsincludelow whitebloodcellandplateletcountsandelevatedliver
enzymes.
What are Causes for Ebola
• EVDin humansiscausedby one of the five strainsof the Ebolavirus – Bundibugyovirus
(BDBV) – Sudanvirus(SUDV) – Taï Forestvirus(TAFV) – Ebolavirus(EBOV) – Restonvirus
(RESTV) All five virusesare closelyrelatedtomarburgviruses
How is Ebola Spread?
• Ebolaisnot an airborne virus.Unlike some otherviruses,the Ebolaviruscanonlybe spread
by bodyfluids.
• Ebolaisintroducedintothe humanpopulationthroughclose contactwiththe blood,
secretions,organsorotherbodilyfluidsof infectedanimalssuchaschimpanzees,gorillas,fruit
bats,monkeys,forestantelope andporcupines
• Ebolathenspreadsthroughhuman-to-humantransmissionviadirectcontact(through
brokenskinor mucousmembranes) withthe blood,secretions,organsorotherbodilyfluidsof
infectedpeople •Andwithsurfacesandmaterials(e.g.bedding,clothing) contaminatedwith
these fluids.

5. •Health-care workershave frequentlybeeninfectedwhiletreatingpatientswithsuspectedor
confirmed EVD.
• Thishas occurredthroughclose contact withpatientswheninfectioncontrol precautions
are notstrictlypracticed.
• Burial ceremoniesinwhichmournershave directcontactwiththe bodyof the deceased
personcan alsoplaya role in the transmissionof Ebola.•People remaininfectiousaslongas
theirbloodcontainsthe virus
• Noformal evidence existsof sexual transmission,butsexual transmissionfromconvalescent
patientscannotbe ruledout.• There is evidence thatlive Ebolaviruscanbe isolatedin
seminal fluidsof convalescentmenfor82 daysafteronsetof symptoms• Evidence isnot
available yetbeyond82 days.There isno evidence of liveEbolavirusinvaginal secretions.
Diagnosis
• Antibody-capture enzyme-linkedimmunosorbentassay(ELISA)
• Antigen-capture detectiontests
• Serumneutralizationtest
• Reverse transcriptase polymerasechainreaction(RT-PCR) assay
• Electronmicroscopyand Virusisolationbycell culture.

6. Prevention & Control
• Most people outsideof WestAfricadonotneedto worryabout Ebolaprevention.Only
those wholive inan area affectedbyEbolaand medical professionalsare indangerof
contractingthe virus
• For those individuals,the CDChasa tip sheetonwaysto preventinfection.
Treatment & Vaccines
• There isno cure for Ebola,nor are there anyvaccinesthatcan preventthe disease.Those
whorecoverfromthe disease dosothroughthe strengthof theirownimmune system
• The incubationperiod,thatis,the time intervalfrominfectionwiththe virustoonsetof
symptomsis2 to 21 days.
• However,arange of potential treatmentsincludingbloodproducts,immune therapiesand
drug therapiesare currentlybeingevaluated.Nolicensedvaccinesare available yet,but2
potential vaccinesare undergoinghumansafetytesting.
• Early,aggressive,intensivecare support:Monitorfluidandelectrolyte balanceandrenal
function,bloodpressure,oxygenation,careful rehydration.
• Supportive drugtherapyincluding:painkillers,antiemeticforvomiting,anxiolyticfor
agitation,+/-antibioticsand/orantimalarialdrugs
• Psycho-socialsupportandservices

7. References
 Virusesandhumandisease byJamesH.Strauss,EllenG.Strauss
 Bats and virusesbyWileyBlackwell
 WHO Report