Ebola Virus Outbreak
2014
What is a Virus?
• Viruses are microscopic particles (10 – 400 nm).
• Viruses are made of genetic material (DNA or
RNA) surrounded by a protein coating and
sometimes an outer layer containing lipids.
• Viruses are not made of cells.
• Viruses must infect cells to make more copies of
themselves.
• A virus cannot reproduce without infecting a
cell and using the components of a host cell to
make more copies of itself.
• The new virus particles then infect other cells to
continue to make more virus particles.
• Antibiotics are not effective against viruses.
What is Ebola Virus?
Credit: NIAID
• Ebola virus is a member of a family of
viruses called Filoviridae.
• Ebola virus particles form long filaments.
• The virus particles contain single-stranded
RNA surrounded a lipid (fatty) membrane.
• The new virus particles bud from the
surface of the host cell.
• Ebola virus was first discovered in 1976
near the Ebola River in Zaire (now the
Democratic Republic of Congo).
• There are four species of Ebola virus that
cause disease in humans. The one causing
the outbreak is a strain of the Zaire species.
What is Ebola Virus Disease?
• The disease caused by Ebola virus is called Ebola Virus
Disease (EVD).
• Ebola Virus Disease is considered a hemorrhagic fever
disease, a type of disease caused by Ebola and other
viruses that is characterized by bleeding and fever.
• The symptoms of EVD include
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Fever
Headache
Vomiting
Diarrhea
stomach pain
muscle pain
bleeding
Credit: Wikimedia Commons
How do you get Ebola?
• It is not easy to catch Ebola virus.
• An infected person is contagious only while they have
symptoms.
• To become infected, a person must have direct contact
with blood or another body fluid, such as feces or vomit,
from an infected person, or with an object that is
contaminated with infected body fluids.
• Following contact, the virus must enter an opening in the
body, like a break in the skin or the eyes, nose, or mouth.
• Ebola virus does not spread through the air, unlike flu.
• In Africa, some people have become infected by handling
bushmeat or through contact with infected bats.
• Family members or healthcare workers are at highest risk
of becoming infected.
How does Ebola make you sick?
Credit: CDC
• Ebola virus infects certain cells of the immune
system, so that they do not function properly.
Instead of protecting a person from infection,
they produce chemicals that cause harm.
• Ebola virus also infects endothelial cells which
line blood vessels.
• Blood leaks out of damaged blood vessels.
• Patients develop very low blood pressures and
go into shock.
• Patients usually die from shock due to fluid loss
rather than actual blood loss.
• Between 25 and 90 percent of patients with
EVD die of the disease. In the current outbreak,
slightly less than half of Ebola victims survive.
What is the treatment for EVD?
Credit: NIAID
• There is no cure for EVD.
• There is no licensed vaccine for EVD.
• There are experimental drugs and vaccines, but
they have not been tested in humans, so it is
not known how effective or safe they are.
• The supply of experimental drugs is very
limited, so there is an ethical dilemma
regarding who should receive the drugs.
• A few patients are receiving blood plasma from
patients who have recovered from Ebola
infection that contains antibodies to Ebola.
• Patients in hospitals are given supportive care
to maintain body fluids, salt levels , and blood
pressure. This improves survival rates.
Where does Ebola come from?
Credit: WHO
• Many viruses that infect humans emerged
from animals.
• A virus can be present in a host animal and not
make them ill, but the virus can be passed to
another animal or a person and make them
sick.
• The natural host of Ebola virus is thought to be
the fruit bat, which in found in regions of
Africa where outbreaks have occurred.
• The first person in an outbreak becomes
infected through contact with an infected
animal.
• The virus can then spread from person to
person.
Why is EVD called an emerging disease?
Credit: NIAID
Credit: CDC
• EVD is considered an emerging infectious
disease.
• An emerging infectious disease is one that
has recently been detected, or a known one
that has appeared in a new place, or one that
is spreading rapidly.
• Emerging infections can be caused by
previously unknown viruses (or other
infectious agents such as bacteria) or viruses
that spread to new locations.
• Other examples of emerging viruses are SARS,
MERS, flu, HIV, and Chikungunya virus.
When and where was Ebola discovered?
Credit: CDC
Credit: Wikimedia Commons
• Ebola was first recognized in 1976 when it
caused two separate outbreaks – one in
Zaire (now the Democratic Republic of
Congo) and the other in southern Sudan.
• The outbreaks were caused by different
species. The Zaire virus caused deaths in
90% of infected people; the Sudan virus
caused deaths in 50%.
• Since then, there have been about 20
outbreaks of Ebola in central Africa with a
total of around 2400 cases and 1600
deaths.
• Because the prior outbreaks occurred in
remote areas, they were easier to contain.
How did the current outbreak begin?
• The first person to become infected was a two
year old boy living in Guinea in December
2013.
• The Ebola outbreak was officially recognized in
March 2014 in Guinea and then quickly spread
to Liberia and Sierra Leone.
• There have been a small number of cases in
Nigeria, Senegal, and Mali, but almost all cases
have been in Liberia, Guinea, and Sierra Leone.
• Ebola transmission has stabilized in Liberia and
Guinea, but remains intense in Sierra Leone.
• By the beginning of December, there have
been in total more than 17,000 cases and
6,000 deaths.
Map showing case numbers in West Africa
The most cases and deaths have occurred in Liberia,Credit: Wikimedia Commons
followed by Sierra Leone, and then Guinea. The rate of new
infections is slowing in Liberia and Guinea but still increasing
in Sierra Leone.
How did Ebola spread to the U.S.?
• Ebola spread to the United States when a Liberian man
who had contact with an Ebola victim flew to Dallas,
Texas. He developed symptoms after arriving in the U.S.
• The hospital did not recognize his illness as Ebola and sent
him home. He returned three days later, was admitted to
the hospital, and died ten days later.
• A nurse who treated this patient tested positive for the
virus. This was the first transmission within the U.S. A
second nurse was also diagnosed with Ebola.
• Both nurses recovered. No further transmission occurred.
• A few patients who became infected in West Africa have
been treated in several locations in the United States and
Europe. In one case, a healthcare worker became
infected in Spain, but no other new infections occurred.
Why is this outbreak so bad?
Credit: CDC
• It started near the borders of three countries
where there is a lot of travel.
• It started in countries where Ebola had not
been seen before, so it had a chance to
spread before it was recognized.
• It went into very densely populated cities
where the virus could spread easily.
• It began in countries with weak healthcare
systems that did not have enough hospital
beds or isolation equipment, and many
healthcare workers became ill and died.
• Response from governments and other
agencies was too slow.
• It spread to new countries by air travel.
How will the outbreak be stopped?
Credit: CDC
• Tracing of all people who had close contact with
an infected person while they were showing
symptoms
• Isolation of all infected people with symptoms
• Improved personal safety procedures and
training for healthcare workers and complete
compliance with these safety procedures
• Implementation of safe burial procedures
• Production of drugs and vaccines
• Containment of the Ebola outbreak in West
Africa to prevent further spread to other
countries
• Learning from this outbreak how to limit future
outbreaks of Ebola or other emerging viruses