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.

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When An Epidemic Becomes a Pandemic

By Medical Discovery News

July 7, 2012

For at least thousands of years, people have suffered flu epidemics and pandemics.  In 412 B.C., Hippocrates described what was likely an influenza epidemic in Ancient Greece. The term influenza comes from 15th century Italy, when people believed stars influenced the illness because it always came in cycles. Soon after, in 1580, the first clear account of a flu pandemic was written. From that point on, records show flu pandemics have been recurring every one to three decades somewhere in the world.

So what is the difference between an epidemic and pandemic? Flu epidemics occur every year because each year the virus comes back just slightly different. In a flu pandemic, a much larger geographic area is affected, sometimes worldwide, when a new strain of the virus infects people for the first time and everyone is susceptible.

The World Health Organization has defined three phases of pandemics. The first, or earliest, is called the Inter-Pandemic period. During this time, no new influenza viruses are detected in humans, but new flu viruses could be circulating in animal populations.

The next level is the Pandemic Alert period. Here, the flu virus is infecting humans but is either incapable or has limited ability for human-to-human transmission. The last is the Pandemic period where there’s widespread and rapid transmission in human populations.

The potential for a flu virus to be capable of causing pandemics lays in its ability to infect many different species including horses, pigs, and birds. As various strains of the flu virus spread from species to species, multiple viruses can infect the same animal, allowing the viruses to exchange genetic information and create a new virus. Once it can infect and efficiently transmit between humans, a pandemic starts.

The annual flu epidemic sickens 20 percent of America’s population and kills 40,000 people, creating a $10 billion loss in productivity and medical costs. Imagine the cost of a pandemic.  The largest recorded was the 1918 Spanish flu pandemic, which killed 675,000 people in America and 20 to 40 million people worldwide.

Today, health officials worry about avian flu (H5N1) and whether, or more likely when, this flu strain will start a new pandemic. The H5N1 virus was first recognized in Hong Kong in 1997.  Since then it has spread extensively throughout Asia and can now be found in the Middle East, Africa, and Europe. The virus is in the Pandemic Alert period with no means yet for extensive human-to-human transmission. As of spring 2012, approximately 600 people have been diagnosed with H5N1 and the mortality rate is an alarming 60 percent.

In order to understand how this virus may attain efficient transmission between people, American and Dutch scientists created a transmissible H5N1 in the lab. The controversial study could help other scientists create a vaccine for when an avian flu pandemic occurs. But others fear this research could provide a “blueprint” for terrorists to create a potential biological weapon.

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