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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From the course by University of Amsterdam
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'll describe the possible modes of
transmission of the virus from animal to person,
and the first zoonotic step and then from human to human or person to person,
and your course and we will discuss
the various bodily fluids
which may lead to transmission due to the containment of the virus.
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 both 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 it's name actually,
or was meant to give it's name to the virus to be more precise and correct.
Where after a first case which surfaced in this hospital,
nosocomial 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're now telling about 40 and we
refer to that already in our epidemiological teaching unit.
Now, what are the animal reservoirs actually?
What is 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
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 rain forest actually,
and then brought back to the village actually where further cases occurred.
We learned that these animals actually are also disease 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 host.
The host actually, which carries the virus,
which contains the virus without falling ill. 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 Abide areas of Central,
West Africa, other parts of Africa, actually.
Now, how do we contract actually the virus?
First of all, the first step is a zoonosis.
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 butchered somewhere deep in the rainforest then eaten
barred 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 role.
This is information leaflet on bushmeat actually and
that one should avoid contact with bushmeat or eating bush meat actually,
particularly during such an outbreak, of course.
But of course as we have learned here and the West African outbreak,
other mechanisms play a role,
Namely: 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 primary rainforest,
now in the West African setting.
Now, once the initial transmission has taken place from a reservoir animal to men,
how is the disease transmitted then from person to person?
So, the transmission between humans occurs
via a direct contact with infected bodily fluids.
The risk of transmission increases once the
patient whom it's has 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 iatrogenic 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 health care workers?
As we have seen during this actual outbreak,
there is a fair amount of health care workers which got infected during the delivery of
health care even in settings where it was clear that they
were dealing with an Ebola patient or a highly suspect patients.
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.
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 buddy system is applied where usually there at least one or two
supervisors who do help the person to get rid of the possibly infected clothing actually.
Delayed diagnosis, of course,
a misdiagnosis of the disease poses a risk factor.
In academic good 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 really take these risks into
account and try to minimize the risk for the healthcare workers actually.
Now, back very briefly to the question whether Ebola viruses are airborne,
at the beginning of this latest outbreak,
the question occurred because one saw that the virus apparently spread rapidly,
there was a 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 extra,
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 been 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 this playing a significant role,
at least up to the time point of creating this slide session actually.
Now, what are our conclusions?
Fruit birds are the most likely natural reservoir actually,
matter of fact 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 deceased people actually.
Now, we're coming to an end of
this teaching unit and I'll see you in the next unit actually.
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