PERSPECTIVEn engl j med 371;12 nejm.org september 18, 20141084An outbreak of Ebola virus disease (EVD) has jolted West Africa, claiming more than 1000 lives since the virus emerged in Guinea in early 2014 (see figure). The rapidly increas-ing numbers of cases in the Af-rican countries of Guinea, Libe-ria, and Sierra Leone have had public health authorities on high alert throughout the spring and summer. More recent events including the spread of EVD to Nigeria (Africa’s most populous country) and the recent evacua-tion to the United States of two American health care workers with EVD have captivated the world’s attention and concern. Health professionals and the general public are struggling to comprehend these unfolding dy-namics and to separate misinfor-mation and speculation from truth.EVD, originally identified in 1976 in Yambuku, Zaire (now the Democratic Republic of Congo), and Nzara, South Sudan, is caused by an RNA virus in the filovirus family. “Ebola” (named after a river in Zaire) encompass-es five separate species — Zaire ebolavirus, Bundibugyo ebolavirus, Taï Forest ebolavirus, Sudan ebolavirus, and Reston ebolavirus. Reston ebolav-irus is not known to cause dis-ease in humans, but the fatality rates in outbreaks of the other four species have ranged from 25 to 90%.1 The strain currently cir-culating in West Africa bears 97% homology to Zaire ebolavirus samples found in the Democratic Republic of Congo and Gabon.2 This strain has historically result-ed in the highest mortality (90%), although the estimated case fatal-ity rate in the current outbreak is less than 60%.3Outbreaks probably originate from an animal reservoir and possibly involve additional inter-mediary species. The most likely reservoir appears to be a fruit bat, although that linkage has not been confirmed.1 Transmission to humans may have occurred through direct contact with tissue or bodily fluids from an infected animal. Notably, Ebola virus is a zoonotic pathogen, and its circu-lation among humans is uncom-mon, which explains the intermit-tent and unpredictable nature of outbreaks. In fact, although the virus has caused more than 20 outbreaks since its identification in 1976, it had caused fewer than 1600 deaths before 2014, with case counts ranging from a hand-ful to 425 in the Ugandan out-break of 2000 and 2001.3 In most instances, the virus emerged in geographically restricted, rural regions, and outbreaks were con-tained through routine public health measures such as case iden-tification, contact tracing, patient isolation, and quarantine to break the chain of virus transmission.Ebola — Underscoring Global Disparities2000CasesDeaths100050001500April 2014No. of Cases and DeathsMay 2014 June 2014 July 2014A BGuinea506 cases/373 deathsLiberia599 cases/323 deathsSierra Leone730 cases/315 deathsNigeria13 cases/2 deathsEbola Virus Cases and Deaths in West Africa (Guinea, Liberia, Nigeria, and Sierra Leone), as of August 11, 2014 (Panel A), and Over Time (Panel B).Data are from the World Health Organization (www.who.int/csr/don/archive/disease/ebola/en).Ebola — Underscoring the Global Disparities in Health Care ResourcesAnthony S. Fauci, M.D.The New England Journal of Medicine Downloaded from nejm.org at WEILL CORNELL MEDICAL LIBRARY on November 10, 2014. For personal use only. No other uses without permission. Copyright © 2014 Massachusetts Medical Society. All rights reserved.n engl j med 371;12 nejm.org september 18, 2014PERSPECTIVE1085Ebola — Underscoring Global DisparitiesIn early 2014, EVD emerged in a remote region of Guinea near its borders with Sierra Leone and Liberia. Since then, the epidemic has grown dramatically, fueled by several factors. First, Guinea, Sierra Leone, and Liberia are re-source-poor countries already cop-ing with major health challenges, such as malaria and other endem-ic diseases, some of which may be confused with EVD. Next, their borders are porous, and movement between countries is constant. Health care infrastructure is in-adequate, and health workers and essential supplies including per-sonal protective equipment are scarce. Traditional practices, such as bathing of corpses before buri-al, have facilitated transmission. The epidemic has spread to cities, which complicates tracing of con-tacts. Finally, decades of conflict have left the populations dis-trustful of governing officials and authority figures such as health professionals. Add to these prob-lems a rapidly spreading virus with a high mortality rate, and the scope of the challenge becomes clear.Although the regional threat of Ebola in West Africa looms large, the chance that the virus will estab-lish a foothold in the United States or another high-resource country remains extremely small. Al-though global air transit could, and most likely will, allow an infected, asymptomatic person to board a plane and unknow-ingly carry Ebola virus to a higher-income country, contain-ment should be readily achiev-able. Hospitals in such countries generally have excellent capacity to isolate persons with suspected cases and to care for them safely should they become ill. Public health authorities have the re-sources and training necessary to trace and monitor contacts. Protocols exist for the appropri-ate handling of corpses and dis-posal of biohazardous materials. In addition, characteristics of the virus itself limit its spread. Nu-merous studies indicate that di-rect contact with infected bodily fluids — usually feces, vomit, or blood — is necessary for trans-mission and that the virus is not transmitted from person to per-son through the air or by casual contact. Isolation procedures have been clearly outlined by the Cen-ters for Disease Control and Pre-vention (CDC). A high index of suspicion, proper infection-con-trol practices, and epidemiologic investigations should quickly lim-it the spread of the virus.Recognizing the signs of EVD can be challenging, however, since early symptoms are nonspecific (see box). It is essential to obtain a careful and prompt travel his-tory. The incubation period typi-cally lasts 5 to 7 days, although it can be as short as 2 days and as long as 21 days. Blood specimens usually begin to test positive on polymerase-chain-reaction–based diagnostics 1 day before symp-toms appear. Typical symptoms include fever, profound weak-ness, and diarrhea. A maculo-papular rash has been described, as have laboratory abnormalities including elevated aminotrans-ferase
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