Ebola virus disease, or EVD, is one of the deadliest viral diseases out there.
Ebola was first discovered in 1976, when two back-to-back outbreaks of hemorrhagic fever
appeared in Central Africa.
In case you need a quick refresher, hemorrhagic fever illnesses usually damage blood vessels,
affect multiple organs in the body, and affect the body’s ability to regulate itself.
Some can cause mild disease, but Ebola and Marburg viruses are notorious for causing
severe disease and high mortality rates.
The first outbreak was in a village near the Ebola River in the Democratic Republic of
Congo, though it was called Zaire back then, and that’s where the virus got its name.
The second outbreak was in a remote village about 500 miles away in what is now South
Sudan.
It turns out that two genetically distinct viruses caused these two outbreaks, and scientists
later discovered that Ebola virus has actually likely existed long before these outbreaks
occurred.
Since then, most of the cases and outbreaks of Ebola virus disease have been somewhere
in Africa, and most of us have probably heard about the major outbreak in West Africa that
lasted from 2014 to 2016.
The outbreak began in a rural area of southeastern Guinea.
It then spread to more urban areas, and became an epidemic in just a few months.
The effects were devastating, with over 28,000 cases and 11,000 deaths.
All in all, the 2014-2016 Ebola epidemic is considered to be the longest lasting, most
fatal, and most geographically extensive epidemic in Ebola’s history.
Let’s dig into what makes this virus so deadly.
Ebola virus belongs to the Filoviridae family, which is a family of filamentous, enveloped,
negative sense single-stranded RNA viruses.
Filoviruses encode just seven proteins in their genome, and under an electron microscope,
the viral particles look like long, stretched filaments.
They can take different forms, either straightened out or curved, and some particles tend to
bend into the shape of the number 6.
Ebola viruses are relatively large, and they’re impressively efficient in the way they replicate.
Even with just seven genes, filoviruses are able to make large amounts of virus and cause
extensive tissue necrosis, meaning cell death, in cells of the liver, lymph nodes, spleen,
and lungs.
Their nucleocapsid is helical, enclosed in an envelope with a single glycoprotein, and
that glycoprotein plays an important role in the infection cycle, as well as all the
destruction that the virus is capable of.
The way that infection happens is this.
First, Ebola virus enters a patient through either a break in the skin or through mucous
membranes.
Depending on the method of entry, the incubation period can last for 6-10 days, and the first
symptoms that appear are usually flulike, although nausea, vomiting, and diarrhea are
also common within the first few days.
From there, the virus migrates from the original site of infection to the lymph nodes, then
gets disseminated to the adrenal gland, liver, and spleen.
As it works its way through the body, Ebola virus destroys a large number and variety
of cells, basically exploding the tissues it comes into contact with.
The virus causes such extreme damage, especially to the gastrointestinal tract, that all body
systems get severely disrupted.
It can also trigger pro-inflammatory cytokines that cause further blood vessel leakage, along
with impaired clotting abilities.
In many cases, this sequence of events results in devastating multi-organ failure and death.
When it comes to diagnosing a case of Ebola virus disease, it can be tricky at first,
since the symptoms can’t necessarily be distinguished from malaria, meningitis, or
typhoid fever in the early stages.
There are multiple lab-based tests that can be employed to get an official diagnosis,
but the samples collected from a patient have to be handled with extraordinary care and
are considered to be extreme biohazard risks.
Essentially, it takes a lot of effort to safely collect and test a suspected Ebola sample.
As far as treatment, supportive care such as intravenous fluids, oxygen therapy, or
medication to stabilize blood pressure or reduce vomiting can improve a patient’s
chances of survival.
Even though there are several experimental treatments that have helped patients with
confirmed Ebola in the past, there are currently no antiviral drugs licensed by the FDA to
treat Ebola virus disease.
There are some drugs being developed to stop the virus from making copies of itself, and
multiple potential treatments being tested, but we don’t yet have a catch-all treatment.
The best way to protect oneself from Ebola is to be aware of how it’s spread, which
is through bodily fluids of people who are ill, either through direct contact or through
items that might have come into contact with an infected person.
And for the record, a person can only spread Ebola to other people once they start to show
signs and symptoms.
This means that healthcare professionals are at an incredibly high risk of exposure, and
they typically have to take extreme measures of protection.
Funeral or burial rituals can be particularly dangerous for those who are burying a previously
infected loved one, as well.
In certain parts of the world, Ebola virus may also be spread through the handling and
consumption of wild animal meat.
As of now, there is an FDA-approved Ebola vaccine available that protects against one
species of Ebola virus, while several more vaccines are being developed and tested.
So although this remains a significant threat, it is hoped that this may change in the coming
decades.