March 2014 marked the starting point of the largest outbreak of Ebola virus disease in history. Although the disease seems to be on a decrease, we are not there yet and new outbreaks will surely emerge. New efforts to combat the outbreak are necessary. This is why we developed this online course about Ebola, targeted at health professionals across the world. In this course you will cover the fundamental knowledge any health professional should have with expected or confirmed cases or a general interest in the Ebola disease. You will discuss the epidemiology of the disease, its pathophysiology and transmission, the clinical presentation including differential diagnosis and confirmation of disease. You will also discuss the general therapeutic approach to the care of Ebola suspected or confirmed patients and discuss the novel vaccine and drug developments. As the Ebola crisis continues to rage through the affected areas, we need health professionals like yourself to be informed and involved. This course is developed in collaboration with colleagues at the University of Amsterdam, the University Medical Center Utrecht (Julius Center/Julius Global Health), Elevate Health, Médecins Sans Frontières and the Lion Heart Foundation.
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Ebola: Essential Knowledge for Health Professionals
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Transmission and natural reservoirs
This learning unit describes the probable transmission routes and reservoir(s) of Ebola viruses, which can cause a wide array of symptoms and are often fatal.
Meet the Instructors
Martin P. Grobusch
Joyce L. BrowneMD, PhD
UMC Utrecht, Utrecht University
Welcome to our learning unit on the transmission of the Ebola virus.
During this session, we would like to achieve the following learning objectives.
Firstly, we will discuss the established and suspected natural animal reservoirs
of the disease of the virus actually, then we will describe the possible modes
of transmission of the virus from animal to person in the first zoonotic step and
then from human to human or person to person in due course.
And we will discuss the various bodily fluids,
which may lead to transmission due to the containment of the virus and
we will also briefly discuss the possibility of an airborne
transmission mechanism of the Ebola virus actually.
So 1976 was the year where two Ebola virus outbreaks occurred in Uganda and
in what was then Zaire and now the Democratic Republic of Congo and
the outbreak which led to the identification of the virus or
the outbreak in a small mission hospital.
Where an initial case surfaced in a very small village close to the Ebola River,
which in the end gave the virus its name, actually or
was meant to give its name to the virus more precise and correct.
And where after the first case, which surfaced in this hospital and
also spread from patient to patient through unsterile
Injection techniques led to the propagation of the virus within
the hospital environment at the hospital community actually.
Now since then, we have seen more outbreaks, of course and we are now
telling about 40 and we refer to that already now epidemiological teaching unit.
Now what are the animal reservoirs?
Actually, what does the natural reservoir of the virus.
For long, actually, we thought that the natural reservoir was big apes.
Actually, because that was what we learned how the virus was transmitted of,
from whom and the first persons in the initial outbreaks
contracted the virus actually, but we now know better.
Because the big apes, or great antelopes, which were hunted down by people,
butchered on the place where they were hunted deep in
the rainforest actually and then brought back to the village.
Actually, where for the cases occurred.
We learned that these animals actually are also diseased by the virus.
So by definition,
it became clear that they couldn't be the main reservoir actually.
It took quite a while and a long,
long search to identify the natural reservoir holes.
The host actually, which carries the virus,
which contains the virus without falling ill and
what happened is that it turned out that this natural reservoir is the or
is the group of fruit bats actually.
These are several species, which do live in spread out of [INAUDIBLE]
areas of central West Africa, the parts of Africa actually.
Now how do we contract actually the virus?
First of all, the first step is zoonosi.
The virus reaches us through contact with bodily
fluids with blood of infected animals,
usually big apes or great antelopes actually.
Which as I said already will be boot shot somewhere deep in the rainforest,
then eaten in part and
then carried back the rest of the meat being carried back to the village.
Now this is how we knew that the virus was transmitted or
initiated small outbreaks in the past, but we learned the hard
way during the outbreak in West Africa that other mechanisms might play a roll.
This is an information leaflet on bush meat actually, and
that one should avoid contact with bush meat or eating bush meat actually,
particularly during such an outbreak, of course.
But of course, as we have learned here in the West African outbreak,
the mechanisms play a role, namely in direct transmission
of the virus through contaminated fruit actually,
where fruit bats may have fed on before.
Actually, this is one of the possible explanations why this
outbreak took root in a large area outside dense,
prime rainforest, now in the West African setting.
Now once the initial transmission has taken place from a reservoir
animal to man, how is the disease transmitted then from person to person?
So the transmission between humans occurs via direct contact with infected bodily
fluids.
The risk of transmission increases once a patient
have massive diarrhea or is bleeding, of course.
But also contact with other bodily fluids, semen, breast milk,
possibly sweat may transmit the disease from one human to another.
As a risk factor of concern, traditional burial
practices have been identified where families,
next family members, friends, next of kin come in close
contact with the body of the deceased individual actually.
What is not entirely clear is whether there is a possibility or
a real risk of ergogenic transmission and
we'll capitalize a bit on this, elaborate a bit on this in due course.
What is important actually is the question of what constitutes risks for
healthcare workers, as we've seen during this actual outbreak.
T here is a fair amount of healthcare workers, which got infected during
the delivery of healthcare even in settings where it was clear that
they were dealing with an Ebola patient or a highly suspect patient.
Of course, needle stick injuries.
Pose a risk that may happen.
There are usually lots of measures in place to reduce this risk,
but also, of course, the non-availability or
the inadequate use of protective clothing plays a big role.
And what has evolved during the outbreak is the knowledge about
the really crucial points, where transmission may occur and
most people would agree that the biggest risk consists in or
occurs in the situation, where the probably exhausted healthcare
worker who has been working in full protective clothing for
a period of time with patients is coming to the exit area of the isolation ward and
starts undressing or taking off the clothing.
We have learned actually that this is a situation of particular risk.
This is where help is needed,
where the body system is applied, where usually,
at least one or two supervisors who do help the person to
get rid of the possibly infected clothing actually.
Delayed diagnosis, of course, or
misdiagnosis of the disease poses a risk factor.
Inadequate training is a problem, actually.
And yeah, these are factors, which are now well understood and most protocols.
All the protocols, which are now applied, and really take these risks
into account and try to minimize the risk for the health care workers actually.
Now back very briefly to the question whether Ebola viruses are airborne.
The beginning of this latest outbreak, the question, yeah,
occurred, because one saw that the virus apparently spread rapidly.
There was large concern about an unusually high number of healthcare workers
getting infected, so the question of Ebola having become airborne arose actually.
Now experimentally in macaque experiments, etc.
It has been shown that indeed, it is possible to create an aerosol,
which contains high numbers of Ebola viruses.
In practical situations in the current outbreak situation,
there is little evidence if at all, that the virus has spread airborne.
We can envisage intensive care settings, actually where
a difficult incubation situation with a patient coughing or
so creates a situation where an aerosol is formed.
And where in theory,
if the protective clothing is not adequate airborne transmission can occur.
But as far as it stands, there is very little evidence for
displaying a significant role at least up to the time point
of creating slide section actually.
Now what are our conclusion?
Fruit beds are the most likely natural reservoir actually, matter-of-factly.
There is very little doubt that they are the natural reservoir.
We know that the virus is transmitted actually,
then later from infected big animals.
Apes, big antelopes, actually, which are butchered and slaughtered.
And then following contact with the bodily fluids or blood and
meat of these butchered animals, the disease transmission changes
from zoonotic transmission to a human to human transmission and
we have briefly discussed which bodily fluids lead to an infection risk.
Actually, in the living and in deceased people actually.
Now we are coming to an end of this teaching unit and
I'll see you in the next unit, actually.
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