Ebola--underscoring the global disparities in health care resources.

n engl j med 371;12 nejm.org september 18, 2014 1084 A 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 increasing numbers of cases in the African countries of Guinea, Liberia, 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 evacuation 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 dynamics and to separate misinformation 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) encompasses five separate species — Zaire ebolavirus, Bundibugyo ebolavirus, Taï Forest ebolavirus, Sudan ebolavirus, and Reston ebolavirus. Reston ebolavirus is not known to cause disease in humans, but the fatality rates in outbreaks of the other four species have ranged from 25 to 90%.1 The strain currently circulating in West Africa bears 97% homology to Zaire ebolavirus samples found in the Democratic Republic of Congo and Gabon.2 This strain has historically resulted in the highest mortality (90%), although the estimated case fatality rate in the current outbreak is less than 60%.3 Outbreaks probably originate from an animal reservoir and possibly involve additional intermediary 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 circulation among humans is uncommon, which explains the intermittent 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 handful to 425 in the Ugandan outbreak of 2000 and 2001.3 In most instances, the virus emerged in geographically restricted, rural regions, and outbreaks were contained through routine public health measures such as case identification, contact tracing, patient isolation, and quarantine to break the chain of virus transmission. Ebola — Underscoring Global Disparities