What is this Ebola thing?

By Antonio Marques • Sep 13th, 2007 • Category: Diseases, Highlight, Medicine, Virus

Ebola makes a tragic return to the Democratic Republic of Congo.

Unfortunately, in the past few days it has been confirmed that the Ebola virus has killed again in the DRC (see map). At least 166 people have died from viral infection and the WHO (World Health Organization) is aware of 206 more cases. This is already considered to be the worst Ebola outbreak in the DRC for several years.

As in any deadly epidemic scenario, there has been a huge effort from Congolese and international authorities to contain the outbreak. Nonetheless, with a mortality rate that can go as high as 90%, for those infected, chances are slim.

The news about this Ebola outbreak has been popping around the web and if you are interested, you can read them in more detail in the following sites (just to name a few):

* Techyum * Health and Nursing Issues Australia * Evolution

* VitaBeat * News-Medical.net * MicrobiologyBytes * Superstrain

But what is this Ebola after all?

The common designation of Ebola virus does not include only one type of virus but is used for a group of viruses that are known for causing the Ebola hemorrhagic fever. The disease, in it’s earlier stages, shows symptoms like high fever, headaches, nausea, etc. which can be confused with more common maladies like malaria or inluenza, thus making the diagnosis harder. In later stages, infection with the Ebola virus leads to severe and bloody diarrhea, vomiting blood and internal and external hemorrhage. Although the symptoms seem quite horrific, the truth is very different. Quoting from Dr. Philippe Calain, CDC Special Pathogens Branch:

At the end of the disease the patient does not look, from the outside, as horrible as you can read in some books. They are not melting. They are not full of blood. They’re in shock, muscular shock. They are not unconscious, but you would say ‘obtunded’, dull, quiet, very tired. Very few were hemorrhaging. Hemorrhage is not the main symptom. Less than half of the patients had some kind of hemorrhage. But the ones that had bled, died.

Methods of Transmission

Ebola is normally transmitted between humans by direct contact with fluids expelled from infected patients. Airborne transmission has been seen but is almost negligent in the overall transmission methods.

So far the animal reservoir for the virus has not been discovered. Although primates are frequently infected (a scenario that is contributing to the extinction of the great apes), the virus is so lethal that prevents them from being the reservoir (the perfect animal species to act as a virus reservoir needs to carry the virus but not be affected by it, allowing for an efficient spreading). The habit of eating monkey meat in certain areas of Congo is one of the causes for transmission between animals and humans.

Ebola mechanisms

The virus’ genetic material consists of a single-stranded, negative-sense RNA. This means that for the virus to replicate, it needs to use a specific RNA polymerase that is contained within the viral particles, turning the genetic material by itself fairly safe.

As with any other virus, Ebola attaches itself to the outside of host cells using specific receptors and manages to gain entry into the cells, releasing the genetic material and other needed proteins for replication. After the RNA polymerase transcribes the viral RNA into mRNA (messenger Ribonucleic Acid), the host cell’s protein synthesis mechanisms start producing new viral particles up to the point when the cell bursts (cell lysis) and releases the newly synthesized virus, which in turn are able to infect neighboring cells. The process goes on until either the individual immune system manages to eliminate the virus or the destruction process is so massive that leads to the host’s death.

Treatments

There is no known treatment for Ebola infection besides primary supportive care. Although vaccines have been developed for monkeys, a human counterpart has not been discovered. Recently, AVI BioPharma reported some success in finding treatments that can be applied against the Ebola and Marburg viruses.

Why Ebola is considered a bad virus

Although Ebola infection is not immediately symptomatic, allowing for some spreading of the virus, the quick way in which kills the host turns it into a bad virus in an evolutionary point of view. It kills faster than it can be transmitted between hosts. Also, not being able to spread through air, reduces it’s chances of transmission. That is why, even if quarantine measures are not perfectly taken, outbreaks are usually restricted to a certain geographical area. All of this is, of course, good news for us.

The bad news are when humans start thinking too much and consider engineering new strains that may increase incubation periods while keeping the same lethality rates: the perfect weapon for biological warfare. Unfortunately….

Want to know more about the Ebola? Here are three recommendations for you: