The filoviridae viruses.
are mid-sized viruses that
contain a filamentus,
enveloped, and helical capsid.
They are linear with a single-stranded,
negative-sense RNA genome,
which means that they must carry an
RNA-dependent RNA polymerase.
The important species that
we'll talk about today
are the Ebola virus,
very recognizable from the colored
photo micrograph on the right,
and a related virus, the Marburg
virus seen here.
The Ebola and the Marburg viruses had
the same mechanism of transmission.
And this slide offered by the CDC,
sort of, shows the typical
collection of factors which ultimately,
wind up in the humans being
This starts with transmission between bats
and other animals in the local area,
typically the jungle,
and these include other primates, small
duiker, elk, etc., and so forth.
And between these animals, there's
an ongoing cycle
until an accidental exposure
to humans occurs.
Rarely is this a bite from one those
animals or exposure to urine,
although that can happen.
More often, it is the human ingesting
bushmeat or meat made from
one of these animals
that itself is infected with or
the Ebola or Marburg virus.
So, we say that it's monkey-human or
but it could be any of the
animals in the jungle
that happens to have been contaminated
with or colonized with the virus,
and then the human is the accidental host.
What happens in terms of pathogenesis?
The target cells for both of these viruses
are primarily endothelial cells, the cells
lining the small blood vessels.
But in addition, phagocytes and hepatocytes
are secondarily infected.
Once the infection occurs,
then the release or the synthesis and
release of the viral glycoprotein
causes extensive toxic damage
to all these tissues.
So, liver, lymph nodes, blood vessels,
spleen, lungs, you name it.
And, of course, because there's an
the overall effect is to have
causing failure in all those organ sites.
In addition, as this is occurring,
then, of course, there's a cytokine
storm, which is sort of like
adding insult to injury. It adds
an inflammatory picture
causing yet still disruption of blood
vessels, vascular leak, etc.
So, let's look at what the clinical
diseases are related to this,
and they're sort of umbrella diagnosed
as African hemorrhagic fever.
The Ebola virus and Marburg virus
both cause this. They're almost
The only change is the location in Africa
where one typically sees these.
So, you are probably familiar with a
fairly recent outbreak in 2014,
2015 in West Africa
that would be Ebola virus.
The Marburg virus more recently has
been found in Uganda.
So both of these, African hemorrhagic
fever, the incubation is up to 21 days.
And in terms of risk exposure,
14-21 days is the most
typical time for onset of disease
The clinical components of a
start with a flu-like illness, just
like many other,
the very nasty infections that
we've talked about.
So, fevers, malaise, headaches,
some coughing, nausea, vomiting, diarrhea,
even a rash, a maculopapular rash.
And as the disease progresses, the
fever becomes higher,
the patient has more malaise,
and they start to develop diffused
myalgias -- muscle pains.
An interesting finding from the
West Africa Ebola outbreak
was that about 15% to 20% of the patients
presented with hiccups, irritation of
the diaphragm causing hiccups.
So that plus flu-like illness plus exposure
to an endemic part of Africa for a virus
should suggest the possible
diagnosis coming up.
Ultimately, over a period of 1 week or so,
patients with the initial presentation
progress to extensive hemorrhage.
And depending on how much virus they
got and where the target was,
the hemorrhage occurred related
to those sites.
Principally, it was gastrointestinal
so extensive hematemesis,
hematochezia -- bloody stools --
absolutely disseminated intravascular
coagulopathy with DIC,
edema, hypovolemic shock, bloody
conjunctivate, you name it.
The mortality in these situations up to 90%.
Without support, 100%.
Even with medical support, the mortality
rate remained at 50%.
There's really not much that one could
do during the course of the illness.
Diagnosis currently by RT
or reverse transcriptase PCR
to be obtained shortly within the
onset, because after
a certain point, the viral RNA
is not detectable.
And treatment is with supportive
care and, of course,
strict isolation using the
approach of clean
to dirty with personal protective
equipment, the PPE,
the so-called space suits that everybody
remembers from the news.
So, these 2 viruses constitute a very
nasty chapter in viral medicine
with a very high mortality rate and,
of course, significant impact
on peoples because of the high
degree of contagiousness,
especially human-human transmission.
So Ebola and Marburg viruses,
the filoviruses, beware.