Ebola is the worst outbreak of the haemorrhagic disease discovered in 1976, some 1 200 people have been killed by the virus from 3 147 cases with a case fatality rate of 56%.
Signs and symptoms of Ebola
Symptoms present themselves anywhere from 2 to 21 days after infection, but mostly between day 8 and 10. The symptoms are similar to the flu, cholera, typhoid and malaria.
Signs and symptoms: Fever, headache, joint and muscle aches, weakness, diarrhoea, vomiting, stomach pain and lack of appetite.
This is followed by vomiting, diarrhoea, rash, impaired kidney and liver function, and in some cases, both internal and external bleeding. Bleeding can occur from the eyes, ears, nose, mouth and anus.
The WHO reports that laboratory findings include low white blood cell and platelet counts and elevated liver enzymes.
People are infectious as long as their blood and secretions contain the virus. Ebola virus was isolated from semen 61 days after onset of illness in a man who was infected in a laboratory.
Science writer David Quammen, who has investigated the origins and spread of the virus, writes that “RNA viruses (of which Ebola is one) produce acute infections, severe for a short time and then gone. Either they soon disappear or they kill you.”
Diagnosing the disease in someone who has been infected for only a few days is difficult because early symptoms, such as eye inflammation and skin rash, resemble symptoms of several other more common conditions.
If Ebola is suspected, laboratory tests should be done promptly. Only one laboratory in South Africa (the National Institute for Communicable Diseases NICD) is equipped to perform tests for Ebola.
This laboratory serves as a World Health Organisation reference centre for haemorrhagic diseases and also provides this diagnostic test service to many other African countries.
There is no treatment or cure.
HOW DOES EBOLA ENTER THE BODY IN THE FIRST PLACE?
Ebola is not known to infect people through the air — you must come into contact with the virus somehow in order to be at risk for infection, Bhadelia said. It’s transmitted through exposure to an animal that carries the virus (such as a bat or primate), through exposure to the bodily fluids of a human who is infected and symptomatic, and through exposure to items that have been contaminated with the virus. People who are “providing care for a household member … when they’re cleaning up vomit or diarrhea, they come into contact [with the virus], and the way it’s transmitted is there’s virus in the fluids,” she said. “That virus gets into your own body through the nose, mouth and such.”
Ebola can also survive outside the host for a significant period of time — as long as a couple of days — at room temperature. “That’s why infection control is such a huge part of this,” Bhadelia said. “If you have sterilization of equipment, if you have availability of disinfectant, things like IVs … and if you’re able to clean all those environments and isolate patients effectively, the outbreak would never take a foothold.” This is why places with good infection control and medical infrastructure face absolutely no risk for outbreaks from this pathogen, she added.
WHAT HAPPENS IN THE BODY ONCE INFECTION OCCURS?
Once the Ebola virus makes its way into the body, it gets in the body’s cells and replicates itself. “Then it comes bursting out of our cells and produces this protein that wreaks havoc,” Bhadelia explained. The protein is called ebolavirus glycoprotein, and attaches to the cells on the inside of the blood vessels. This increases permeability of the blood vessels — leading to blood leaking out of the vessels. “The virus causes derangement in the body’s ability to coagulate and thicken the blood,” she said. Even people who don’t show hemorrhagic symptoms will experience this leaking of blood from the vessels — which can eventually lead to shock and, ultimately, death.
The Ebola virus is also a master of evading the body’s natural defenses: It blocks the signaling to cells called neutrophils, which are white blood cells that are in charge of raising the alarm for the immune system to come and attack. In fact, Ebola will infect immune cells and travel in those cells to other parts of the body — including the liver, kidney, spleen and brain.
Each time one of the cells is infected with the Ebola virus and bursts, spilling out its contents, the damage and presence of the virus particles activates molecules called cytokines. In a healthy body, these cytokines are responsible for provoking an inflammatory response so that the body knows it’s being attacked. But in the case of an Ebola patient, “it’s such an overwhelming release [of cytokines], that’s what’s causing the flu-like symptoms” that are the first sign of Ebola, Bhadelia said.
WHAT DO THE SYMPTOMS LOOK LIKE?
Ebola generally starts with flu-like symptoms. Though it’s known for the extreme hemorrhagic symptoms — the bleeding out of the eyes, etc. — not everyone will experience these. “In fact, only 20 percent of people will have [these extreme symptoms]” Bhadelia said. “Some people may succumb to the illness before it gets to that point, some may have minor bleeding, some may just have bleeding of the gums, or bruising.”
HOW IS IT THAT SOME PEOPLE HAVE SURVIVED THE DEADLY INFECTION?
It largely has to do with two factors. The first is the person’s health in general — his or her immune system and ability to bounce back from a viral infection. The second is the type of exposure he or she got. Recovery may be more likely if it wasn’t a severe exposure — meaning, perhaps they were exposed to someone who was only early on in the illness, and the amount of virus in the bodily fluids was not yet that high, Bhadelia said.
In addition, what is known about Ebola is that it requires a known marker on the surface of human cells themselves, which it uses to gain entry into the cells. Researchers have found in a laboratory setting that some people’s cell lines actually lack this marker, or it may be mutated somehow, so that the Ebola can’t get into the cells. However, Ebola research is still very much in its infancy, and knowledge about how the virus behaves is still evolving, Bhadelia said.
Still, findings like these do pave the way for potential treatments. Right now, she said, research is being done to develop treatments that work in several different ways. One of the ways is to block the virus from replicating itself once it’s inside the cell. “It basically provides a full stop and doesn’t let the virus copy its genetic material over and over again to create the new viruses,” Bhadelia said. Another way is to help the body’s immune system create an effective response to Ebola by exposing the immune system to an attenuated version of the virus. That way, “it can create an effective response so when the real virus comes around, the immune system doesn’t get evaded the way it does regularly.” And yet another way is to actually create antibodies specifically against the virus, so “you’re giving the immune system a boost from the outside,” she said.