The Ebola Virus

Ebola and a similar viruses the Marburg virus.

There is a lot of news lately regarding the Ebola virus. How it is spreading and how dangerous it is. However, this virus is similar to another virus, the Marburg that can affect the body in similar ways. For example, signs and symptoms usually begin within 5 to 10 days after the infection with Ebola or Marburg virus has occurred.

The Filoviridae virus family.

There are three virus members in the Filoviridae family. The Genus EbolaVirus, is one, and the genus Marburgvirus and genus Cuevavirus are the other two.

Genus Ebolavirus is made up of 5 distinct species:

Bundibugyo ebolavirus

Zaire ebolavirus

Reston ebolavirus 

Sudan ebolavirus

Taï Forest ebolavirus 

The Genus Marburgvirus is made up of 2 distinct species:

Marburg virus and Ravn virus

The most recent genus is the Cuevavirus addes in 2010.

In general, what are these viruses?

The Ebola and Marburg virus are related because they cause severe fevers. These are illnesses marked by severe bleeding called a hemorrhage. There is also the possibility of organ failure and, which can cause death. Both viruses occur in Africa where these outbreaks have occurred for decades. Marburg virus and Ravn virus (2), which are approximately 20% divergent from one another

What are some of the effects of these viruses?

The effects include fever, joint and muscle aches, severe headache, chills, and body weakness.

However, after a time, the symptoms become more severe and additional body impacts occur such as nausea and vomiting, chest pain and cough, diarrhea, rash, stomach pain, severe weight loss, and red eyes. In addition, other bleedings may occur. Some will come from the eyes, and also bruising can occur where people near death may bleed from other areas like ears, nose, and rectum.  

Causes of the viruses spread

Both Ebola and Marburg virus originate from animals. Both have been found inside African monkeys, and chimps in addition to non-human primates. There also has been some evidence linking the Marburg virus to fruit bats in Africa.

How does the transmission from animals to humans occur?

At this time, the science evidence points to infections that occur from both viruses, which have infected transmissions to humans through the animal's bodily fluids. Examples include:

Blood products. When people butcher or eat infected animals this can spread the viruses. While carefulness is important, and as part of their research, even scientists who have operated on infected animals have also contracted the virus.

Animal waste products also form a basis of transmission. Tourists who have entered African caves and mine workers working underground have been infected with the Marburg virus, in part because they have had contact with infected bats and their spillover like the feces or urine.

At this time, there's no evidence that either the Ebola virus or the Marburg virus can be spread from insect bites.

How does the transmission from person to person occur?

Infected people ordinarily do not become contagious until after they develop symptoms. Family members, however, can become infected as they care for sick relatives or prepare a burial for the dead.

The Death Rate

Why are these viruses are so deadly? It involves the immune system. These viruses interfere with the system's ability to protect the body. Both Ebola and Marburg can lead to a high percentage of death for infected victims. The current death rate is 90%. So what happens to people that are infected? The virus can cause multiple organ failure, severe bleeding, coma, shock, jaundice, seizures, and delirium.

One of the current science and medical mysteries is that it is not clear why some people recover from Ebola or Marburg virus but others do not.

The Evolution of the Ebola and Marburg Virus

While media attention has been focused on the deadly aspects of these viruses, another science and evolutionary aspect is present.

These viruses are relatively new.

Ebola first appeared in 1976 in simultaneous outbreaks located in Nzara, Sudan, and in Yambuku, in the Democratic Republic of Congo. Because Yambuku is a village situated near the Ebola River, the disease takes its name from there.

As these diseases originated with similar DNA sequences, what became important is how they continue to spread. It turns out that RNA is the prevailing sequence. In studying the DNA for Filoviruses, it became understood that they reproduce as RNA. The instance then showed that even though they reproduced over 20 years when they were first studied from 1976 to 1996, the original RNA format was stable.

One of the operating standards regarding these viruses is that the evolution originated with animals, but the virus found a steady and consistent approach to spreading inside the body of the animals. It didn’t change over time.

However, at the DNA level, how often is there a substitution? The following table give a general description:

The changes shown by the molecular evolutionary rate identify the rate.

Looking at the molecular evolutionary rates for viruses belonging to different species range from 0.46 × 10(-4) nucleotide substitutions/site/year for Sudan ebolavirus to 8.21 × 10(-4) nucleotide substitutions/site/year for Reston ebolavirus.

What this means is that the changes, which are the nucleotide substitutions, occur very rarely. A nucleotide mutation alters the amino acid sequence of a protein. 

So the most recent common ancestry can be traced back only within the last 50 years for two viruses the Reston ebolavirus and the Zaire ebolavirus species. What this suggests is that viruses within these species may have undergone recent genetic bottlenecks preventing them from acting. On the other hand, viruses within Marburg and Sudan ebolavirus species can be traced back further and share most recent common ancestors approximately 700 and 850 years before the present, respectively. However, scientists looking at the whole family of virus have presented suggestions that members of the Filoviridae virus share a recent common DNA ancestor originating approximately 10,000 years ago.

Summary

Both Ebola and Marburg viruses originate with animals in Africa. Contact with the animals will spread the virus to humans. Humans can spread the virus to other humans if either one encounters another person and then gets exposed to human fluids. The overall consequences can be deadly. At this time, there is no cure.

The evolution of the viruses can go back to 10,000 years for the Filorivide, and 700 to 850 years for versions of the Ebola and Marburg virus and most recently 50 years for the other versions of the Ebola virus.