Chapter 24: Ebola and Marburg Virus

INTRODUCTION

Ebola virus disease is caused by infection with the filovirus Ebolavirus. Five different species have been identified, and the vast majority of cases and outbreaks have been caused by the Zaire species. The Ebola virus was first recognized during outbreaks in Sudan and Zaire in 1976.¹ Since then, intermittent outbreaks caused by the virus have occurred mostly in sub-Saharan Africa. The largest known outbreak occurred between 2013 and 2016, producing an epidemic in West Africa with nearly 29,000 known or suspected cases and over 11,000 deaths.¹ Ebola virus disease has also proven to be highly contagious, and appropriate infection control measures have been essential in managing epidemics in Africa as well as in preventing spread where cases have been identified and managed in the United States and Europe.¹ Early diagnosis and prompt initiation of supportive care are essential to decreasing both mortality and transmission of the virus. This chapter will also discuss the closely related Marburg virus, which was the first identified filovirus, but has been much less commonly encountered in recent years.

EBOLA

Epidemiology and Risk Factors

The Ebola virus has caused more than 20 outbreaks in sub-Saharan Africa since it was first identified in 1976 (Figure 24-1). Most Ebola virus disease outbreaks have occurred in small and isolated regions of central Africa or Sudan. While often devastating to the local populations, these outbreaks have generally not caused widespread epidemics, likely due to low population density and limited travel by infected populations. The largest outbreak occurred in West Africa from 2013 to 2016, primarily in Guinea, Sierra Leone, and Liberia, causing more than 11,000 deaths, though due to under-reporting the toll could have been considerably higher.^1–3 This recent epidemic showed that the virus has a potential for wide and rapid spread both in urban areas and across international borders. A few secondary infections were noted in the nurses of Spain and the United States, who had cared domestically for infected patients returning from endemic areas.³ Since 2018, there have been multiple outbreaks in the Democratic Republic of the Congo as well, with over 2,000 deaths reported.^1–3

Ebola virus disease is thought to be a zoonotic disease, possibly residing in fruit bats though this has not been rigorously proven. Initial human infection is likely caused by either the handling of infected wild animals such as chimpanzees and gorillas for meat, or by exposure to infected bats. Human-to-human transmission occurs via contact with mucous membranes or broken skin with infected body fluids, primarily blood, feces, and vomit. Sexual transmission has also been reported. The potential for aerosol and airborne transmission is debated.²

Treating infected patients ...