Most researchers believe that the first outbreak of Ebola happened in 1976, in the Democratic Republic of Congo (then known as Zaire).
The current outbreak of the virus which began in early 2014 in West Africa has infected more than 27,000 people and killed nearly 11,200.
However, the Ebola virus may be quite old; previous research discovered remnants of identical Ebola DNA in several different species of rodents, including the mouse and the Norway rat.
This led scientists to speculate that Ebola infected the ancestors of these species at least 20 million years ago.
Kazanjian suggests that an Ebola virus may have been the culprit in the infamous Plague of Athens, a five-year epidemic that began in 430 BC, whose cause has long been a matter of conjecture among physicians and historians.
The Athenian illness began with an abrupt onset of fever, headache, fatigue, and pain in the stomach and extremities, accompanied by furious vomiting. Those who survived after seven days of illness also experienced severe diarrhea.
In the ancient world, sub-Saharan Africans migrated to Greece to work as farmers or servants, thereby providing a potential human vector for Ebola.
Kazanjian argued that the symptoms, mortality rate and origin in sub-Saharan Africa that characterise the Plague of Athens are consistent with what is known about Ebola.
He added that physicians were among the first victims of the Athenian disease, just as modern health care workers have proven especially vulnerable to Ebola, with nearly 500 dying from the virus in the current outbreak as of January.
The study was published in the journal Clinical Infectious Diseases.
