Filoviridae is a family of viruses that includes some of the most virulent human pathogens known, such as Ebola virus and Marburg virus. These viruses are responsible for severe hemorrhagic fevers in humans, with case fatality rates that can exceed 90%. The name Filoviridae comes from the Latin filum, meaning thread, referring to the characteristic filamentous shape of these viruses.
Filoviruses are negative-strand RNA viruses and members of the order Mononegavirales. They are enveloped viruses with a non-segmented genome ranging in size from 18 to 34 kilobases. The viral genome encodes seven proteins: nucleoprotein (NP), VP35, VP40, glycoprotein (GP),VP30, VP24, and L protein. The NP forms the helical scaffold around which the other proteins assemble to form the virion core. GP is a type I membrane protein that is responsible for attachment of the virus to host cells and entry into those cells. It also serves as a receptor for antibodies during infection.
Ebola virus (EBOV) and Sudan virus (SUDV) are members of the genus Ebolavirus; Marburg virus (MARV) is the sole member of the genus Marburgvirus. There are five identified species within Ebolavirus: Zaire ebolavirus (the most studied and most virulent), Bundibugyo ebolavirus (BDBV), Sudan ebolavirus (SUDV), Tai Forest ebolavirus (TAFV; also called Cote d’Ivoire ebolavirus), and Reston ebolavirus (RESTV). However, only three – Zaire, Sudan, and Reston – have caused disease in humans. EBOV was first identified in 1976 in outbreaks of hemorrhagic fever in Sudan and Democratic Republic of Congo; SUDV was identified in an outbreak in Sudan in 1979; MARV was first identified during outbreaks of hemorrhagic fever in Germany and Yugoslaviain 1967; TAFVEBOV emergedin 1994in Ivory Coast; finally RESTVEBOVDid not cause any human cases until it was discovered accidentallyin 1989during importationof infected monkeysinto Virginiafrom Philippinesfor research purposes(hence its name).
The natural reservoirsfor Ebolaand Marburgvirusesremain unknownalthough batshave been incriminatedas likely hostsbased on studiesdetectingthe presenceof these virusesin various speciesof African batswithout any apparent signsor symptoms ofthedisease(termed asymptomatic or subclinical infections). It is hypothesizedthat infected animals shed live virusthrough their bodily fluidswhich could then contaminate either other animalsor humanscoming intocontactwith themdirectlyor indirectly through contaminated food or water sourcesresulting innosocomial transmission chains particularlyinthe settingsof poor hygieneand sanitation conditions especially prevalent insub-Saharan Africa wheremost outbreaks have occurredto date . Oncehumans becomeinfected they can furthertransmitthe disease tothenosexually throughsemen evenafterrecovery fromtheacutephaseofthe illnesshas resolved orverticallyfrom motherto child person-to-person through contactwith blood bodyfluidsor tissuesof infectedsubjects orobjectsthat have beentaintedwith these fluids including beddingclothingor medicalequipment . nosocomialtransmissioncanalso occurwhen healthcareworkerscome intocontactwith patientswho havenot yet been diagnosed resultinginnumerousoutbreakswith highmorbidityand mortalityparticularly among healthcarestaff caringforthe patientsdirectly .
Thereis currently no specific therapyordrugavailablefor treatmentof infectionby anyfiloviruselicensingproceduresfor investigationalnew drugsare ongoing butno product hasyet reached clinicaltrial stage . Treatmentis thus mainlysupportiveconsistingoffluid replacementmaintainingelectrolyte balance addressingany secondarycomplicationsas theyariseand providing psychologicalsupporttopatientsandi their families . Preventionrelies on identifyingcases early topreventfurtherspreadsthrough promptisolationofthe patient contacttracingandsupportivecare offamily membersandalso on educating communitiesabout risk factors Transmissioncanbe reducedby practicinggoodhandhygiene usinguniversalprecautionswearingprotective clothing when exposedto potentiallyinfectiousmaterialsand by avoiding closecontactwith sick individuals particularlythose withsymptoms suggestiveoffeverbleedingorpainfululcerations .