The Birth of Ebola

May 1, 2015

By Medical Discovery News

Colorized micrograph of Ebola by Dr. F.A. Murphy

For most Americans, the Ebola scare seems to have come and gone, but that doesn’t mean the outbreak is over in Africa or that we’ve seen the last of the virus, especially considering its history. Scientists believed that Ebola is relatively new as far as viruses go – only 10,000 years old. However, ancient animal bones show that Ebola appeared between 16 and 23 million years ago, perhaps even earlier.

The Ebola virus was discovered in 1976 during two outbreaks in what was then called Northern Zaire (now the Democratic Republic of the Congo) and Southern Sudan. The outbreaks were actually caused by two different strains of the Ebola virus named Zaire and Sudan, with 90 and 50 percent mortality rates respectively. Since then, three other strains have been identified: Tai Forest, Bundibugyo, and Reston, which is the only one that doesn’t affect people. Overall, there have been 27 outbreaks, but the current outbreak that started in March 2014 is by far the worst, infecting almost 25,000 people and killing over 10,000, thereby making it the world’s first Ebola epidemic.

Ebola is a member of the filovirus family, which also includes the Marburg virus discovered in 1967. Filoviruses are zoonotic, meaning they replicate in other animals, their natural reservoirs, before transmitting to humans. The Ebola virus’s natural reservoir is African fruit bats, so it can transfer to humans who come into contact with an infected bat or another species that has been infected, such as chimpanzees, antelope, and porcupine. Then the virus can spread from person to person.

New research into the origins of filoviruses shows that they have evolutionary ties that go back millions of years. Scientists tracked the viruses’ origins by looking for pieces of their genetic information in fossilized animal bones. While using the bones to study the genomes of ancient voles and hamsters, they found the same pieces of the viruses’ genetic material in the same locations in both rodent species. This suggests that the viruses have existed at least as long as the two species have.

Given the billions of bases each animal has in its genome, it is highly unlikely that these fragments of viral genetic information would have been inserted in exactly the same locations during different infections. Scientists therefore concluded that the virus had infected a common ancestor of these two rodents sometime before the Miocene Epoch, 5-23 million years ago, around the time the great apes arose. Furthermore, the viral genetic elements more closely resemble Ebola than Marburg, meaning the two viruses had already diverged from each other. Sometime before then, the two viruses shared a common ancestor that has not yet been identified.

This means that these viruses have been coevolving with mammals for millions and millions of years, much longer than previously believed. An understanding of the origins and evolution of filoviruses could help us better prevent outbreaks of them and hopefully even create a vaccine that would be effective against all of them.

For a link to this story, click here.

The Bright Side of Black Death

April 17, 2015

By Medical Discovery News

Bright Side of Black Death

It’s easy to think that nothing good could come from a disease that killed millions of people. But Dr. Pat Shipman, an anthropologist at Pennsylvania State University, disputed that notion in his recent article in “American Scientist,” where he suggested the Black Death that ravaged Europe in the Middle Ages may have resulted in some positive effects on the human population. Considering that we are in the midst another significant plague (the Ebola virus in West Africa), we could certainly use more information about the role of pandemics on human populations.

The Black Death or Bubonic plague started in the mid-1300s and was caused by a bacterium called Yersinia pestis, which typically enters the body through the bite of a flea. Once inside, the bacterium concentrates in our lymph glands, which swell as the bacteria grow and overwhelm the immune system, and the swollen glands, called buboes, turn black. The bacteria can make their way to the lungs and are then expelled by coughing, which infects others who breathe in the bacteria. The rapid spread of the infection and high mortality rates wiped out whole villages, causing not only death from disease but starvation as crops were not planted or harvested. It killed somewhere between 100 million to 200 million people in Europe alone, which was one-third to one-half of the entire continent’s population at the time. The plague originated in the Far East and spread due to improved trade routes between these two parts of the world.

Today, global travel is easier than ever thanks to extensive international airline networks. Just like with the Black Death, our transportation systems could enhance the spread of a modern plague. Of course, modern healthcare is also more sophisticated and effective, but as the latest Ebola outbreak has reminded us, a pandemic is a realistic possibility.

Dr. Sharon DeWitte, a biological anthropologist at the University of South Carolina, recently made several discoveries from comparing the skeletal remains of those who died from the Black Death and those who died from other causes during the same era. First, she found that older people, who were therefore already frail, died at higher rates. Killing this group at a higher rate created a strong source of natural selection, removing the weakest part of the population.

After the plague years, she found that in general people lived longer. In medieval times, living to 50 was considered old age. But the children and grandchildren of plague survivors lived longer, probably because their predecessors lived long enough to pass on advantageous genes. Today, a genetic variant in European people called the CCR5-D32 allele, which was favored during the natural selection initiated by the plague, is associated with a higher resistance to HIV/AIDS.

Microbes have an intimate relationship with human populations and have shaped human evolution through the ages. We may see survivors of the Ebola virus passing on similarly advantageous genes through natural selection as well.

For a link to this story, click here.

Viruses Up to Bat

April 11, 2014

By Medical Discovery News


In tales, bats are feared because they could be blood-sucking vampires in disguise. Obviously, Dracula isn’t real, but science has recently uncovered a dark secret that bats have been keeping: viral reservoirs.

Reservoirs are bodies of collected water. Viral reservoirs are a collection of viruses carried by one species. Bats are an important source for a variety of viruses that can infect other animals and humans, such as deadly viruses SARS, Ebola, and MERS.

Bats are among the most abundant and diverse vertebrates on earth and are found on every continent except Antarctica. Their ability to maintain viruses may date back to ancient times. Viruses can cause persistent infections in bats or they can lay dormant. Since bats also have relatively long lifespans – up to 25 years – if they have a persistent virus they have a good chance of infecting others with it, especially since they can fly and travel long distances. Bats also live in close-knit communities, so they are likely to pass infections to other bats, thereby maintaining viruses in the population. Some viruses spread by direct contact, while others such as rabies can be spread by droplets of saliva, mucus, urine, or feces. 

While scientists have known for a while that bats are a source of the rabies virus, they have recently isolated almost 70 other viruses from bats. Most of these only infect fellow bats, not other animals or people, but they do carry some dangerous human pathogens like Japanese Encephalitis, Chikungunya, Rift Valley Fever, Nipah viruses, and Hendra viruses. 

Henipaviruses were first discovered as the cause of an outbreak of an acute respiratory illness in two humans and 22 horses in Hendra, a suburb of Brisbane, Australia, in 1994. The virus kills 75 percent of horses who are infected and 60 percent of people. That’s an especially deadly virus. Since then, there have been 39 Hendra outbreaks in horses, two of which spread to people. That virus was later found to be genetically related to another virus called the Nipah virus, which emerged in Malaysia in 1999. There have been nine more outbreaks of the Nipah virus since then, killing almost half of the people infected. Bats were probably responsible for many of these outbreaks.

In the latest study, 42 percent of the 2,000 Straw-coloured Fruit Bats from 12 African countries harbored Henipaviruses. About one-third of the bats also carried a rabies-like virus called Lagos bat virus. Since Henipaviruses can be easily transmitted, people living near bat populations could be at risk of infection.

Before mass bat hunts begin, it’s important to know that bats play essential roles in the ecosystem and cannot be eliminated without drastic consequences. Therefore people need to be cautious and vigilant about potential exposure to bat viruses. Ongoing research will hopefully create new antiviral vaccines that protect people. As humans continue to invade wildlife areas, so will the possibilities of contracting new viral infections. 

For a link to this story, click here.