Ebola Virus Disease (EVD)
Ebola Virus Disease (EVD) is a highly contagious disease that is caused by five different strains of the Ebola virus;
these viruses have affected humans and animals such as pigs, monkeys, chimpanzees, and gorillas. First
discovered in 1976, the ebola virus has been a cause of several outbreaks in Africa where it also reached other
countries including Italy, Spain, Russia, Philippines, USA, and United Kingdom.
What is Ebola Virus Disease (EVD)?
Ebola Virus Disease (EVD) is a highly contagious disease that causes fever, weakness,
diarrhea, and unexplained bleeding.
● It was previously called ‘Ebola Hemorrhagic Fever’ because the virus circulates
throughout the body and harms the immune system and organs. Eventually, it leads
to severe uncontrollable bleeding.
● Ebola virus was first discovered in 1976 near the Ebola River in what is now the
Democratic Republic of Congo.
● The viruses that cause EVD are located mainly in sub-Saharan Africa.
● In patients who have Ebola virus infection, exposure to the virus may be either
primary (involving presence in an Ebola Virus -endemic area) or secondary (involving
human-to-human or primate-to-human transmission).
Classification
The five ebolavirus species were named for the locations where they caused documented human
or animal disease.
● Sudan ebolavirus & Zaire ebolavirus. Two African species, Sudan ebolavirus and
Zaire ebolavirus (most lethal of all species of the ebola virus) have been responsible
for most of the reported deaths.
● Ivory Coast ebola virus. Clinical disease due to African-derived Ebola virus is
severe and, with the exception of a patient who survived infection with a third African
species, Ivory Coast ebola virus, is associated with a mortality ranging from 65%
(Sudan, 1979) to 89% (Democratic Republic of the Congo [DRC], December 2002 to
April 2003).
● Reston ebolavirus. A fourth Ebolavirus species, Reston ebolavirus, was first
isolated in 1989 in monkeys imported from a single Philippine exporter; a virtually
identical isolate imported from the same Philippine exporter was detected in 1992 in
Siena, Italy.
● Bundibugyo ebolavirus. The fifth Ebolavirus species, also of African lineage, is
Bundibugyo ebolavirus, which caused an outbreak in Uganda in 2007-2008, with a
mortality of 25%.
, Pathophysiology
Ebola virus has a nonsegmented negative-stranded RNA genome containing 7 structural and
regulatory genes.
● After infection, human and nonhuman primates experience an early period of rapid
viral multiplication that, in lethal cases, is associated with an ineffective immunologic
response.
● Viral replication is accompanied by widespread and severe focal necrosis.
● The most severe necrosis occurs in the liver, and this is associated with the
formation of Councilman-like bodies similar to those seen in yellow fever.
● In fatal infections, the host’s tissues and blood contain large numbers of Ebola
virions, and the tissues and body fluids are highly infectious.
Causes
Scientists think people are initially infected with Ebola virus through contact with an infected
animal, such as a fruit bat or nonhuman primate; this is called a spillover event; after that, the
virus spreads from person to person, potentially affecting a large number of people.
● Contaminated blood or body fluids. Blood or body fluids (urine, saliva, sweat,
feces, vomit, breast milk, and semen) of a person who is sick with or has died from
Ebola virus disease (EVD).
● Contaminated objects. Objects (such as clothes, bedding, needles, and medical
equipment) contaminated with body fluids from a person who is sick with or has died
from EVD.
● Vectors. Infected fruit bats or nonhuman primates (such as apes and monkeys).
● Contaminated semen. Semen from a man who recovered from EVD (through oral,
vaginal, or anal sex). The virus can remain in certain body fluids (including semen) of
a patient who has recovered from EVD, even if they no longer have symptoms of
severe illness. There is no evidence that Ebola can be spread through sex or other
contact with vaginal fluids from a woman who has had Ebola.
Statistics and Incidences
Ebola virus disease (EVD), one of the deadliest viral diseases, was discovered in 1976 when two
consecutive outbreaks of fatal hemorrhagic fever occurred in different parts of Central Africa.
Ebola Virus Disease (EVD) is a highly contagious disease that is caused by five different strains of the Ebola virus;
these viruses have affected humans and animals such as pigs, monkeys, chimpanzees, and gorillas. First
discovered in 1976, the ebola virus has been a cause of several outbreaks in Africa where it also reached other
countries including Italy, Spain, Russia, Philippines, USA, and United Kingdom.
What is Ebola Virus Disease (EVD)?
Ebola Virus Disease (EVD) is a highly contagious disease that causes fever, weakness,
diarrhea, and unexplained bleeding.
● It was previously called ‘Ebola Hemorrhagic Fever’ because the virus circulates
throughout the body and harms the immune system and organs. Eventually, it leads
to severe uncontrollable bleeding.
● Ebola virus was first discovered in 1976 near the Ebola River in what is now the
Democratic Republic of Congo.
● The viruses that cause EVD are located mainly in sub-Saharan Africa.
● In patients who have Ebola virus infection, exposure to the virus may be either
primary (involving presence in an Ebola Virus -endemic area) or secondary (involving
human-to-human or primate-to-human transmission).
Classification
The five ebolavirus species were named for the locations where they caused documented human
or animal disease.
● Sudan ebolavirus & Zaire ebolavirus. Two African species, Sudan ebolavirus and
Zaire ebolavirus (most lethal of all species of the ebola virus) have been responsible
for most of the reported deaths.
● Ivory Coast ebola virus. Clinical disease due to African-derived Ebola virus is
severe and, with the exception of a patient who survived infection with a third African
species, Ivory Coast ebola virus, is associated with a mortality ranging from 65%
(Sudan, 1979) to 89% (Democratic Republic of the Congo [DRC], December 2002 to
April 2003).
● Reston ebolavirus. A fourth Ebolavirus species, Reston ebolavirus, was first
isolated in 1989 in monkeys imported from a single Philippine exporter; a virtually
identical isolate imported from the same Philippine exporter was detected in 1992 in
Siena, Italy.
● Bundibugyo ebolavirus. The fifth Ebolavirus species, also of African lineage, is
Bundibugyo ebolavirus, which caused an outbreak in Uganda in 2007-2008, with a
mortality of 25%.
, Pathophysiology
Ebola virus has a nonsegmented negative-stranded RNA genome containing 7 structural and
regulatory genes.
● After infection, human and nonhuman primates experience an early period of rapid
viral multiplication that, in lethal cases, is associated with an ineffective immunologic
response.
● Viral replication is accompanied by widespread and severe focal necrosis.
● The most severe necrosis occurs in the liver, and this is associated with the
formation of Councilman-like bodies similar to those seen in yellow fever.
● In fatal infections, the host’s tissues and blood contain large numbers of Ebola
virions, and the tissues and body fluids are highly infectious.
Causes
Scientists think people are initially infected with Ebola virus through contact with an infected
animal, such as a fruit bat or nonhuman primate; this is called a spillover event; after that, the
virus spreads from person to person, potentially affecting a large number of people.
● Contaminated blood or body fluids. Blood or body fluids (urine, saliva, sweat,
feces, vomit, breast milk, and semen) of a person who is sick with or has died from
Ebola virus disease (EVD).
● Contaminated objects. Objects (such as clothes, bedding, needles, and medical
equipment) contaminated with body fluids from a person who is sick with or has died
from EVD.
● Vectors. Infected fruit bats or nonhuman primates (such as apes and monkeys).
● Contaminated semen. Semen from a man who recovered from EVD (through oral,
vaginal, or anal sex). The virus can remain in certain body fluids (including semen) of
a patient who has recovered from EVD, even if they no longer have symptoms of
severe illness. There is no evidence that Ebola can be spread through sex or other
contact with vaginal fluids from a woman who has had Ebola.
Statistics and Incidences
Ebola virus disease (EVD), one of the deadliest viral diseases, was discovered in 1976 when two
consecutive outbreaks of fatal hemorrhagic fever occurred in different parts of Central Africa.
