A young girl gets the smallpox vaccine, which eventually eradicated the devastating disease that killed hundreds of millions.
History has been largely defined by epidemics and pandemics that destroyed entire populations and brought down civilizations.
Because of its extreme lethality and lack of proven treatments, Ebola raises fears that such apocalyptic events could return. Ebola is also a reminder that the natural state of humanity is a struggle against infectious diseases that often are deadlier than human enemies.
Doctors and scientists have devised countermeasures such as improved hygiene, vaccination and control of animals that spread pathogens. In the past half-century, they’ve given developed countries an unprecedented break from the most deadly diseases.
But that respite is fragile. As people delve deeper into remote corners of the world, they increasingly encounter unfamiliar viruses that are typically harmless to their animal hosts but deadly in humans. This is what researchers believe happened with both HIV and Ebola.
First identified in 1976, Ebola has been traced to remote jungles in the Democratic Republic of Congo, which straddles central Africa. Every so often, the virus jumps to people.
Just how Ebola makes these periodic leaps isn’t known for sure. Fruit bats are the prime suspect; they’ve shown signs of Ebola infection. Moreover, the bats don’t seem to be harmed by Ebola, a sign that the virus may make its natural home in them.
Researchers theorize that cross-species infection happens when people eat fruit bats, and the bats also leave saliva or feces on fruit that people may consume. These body excretions are known to carry live Ebola viruses.
Warning poster in Liberia.
— CDCWarning poster in Liberia. / CDC
Major uncertainties
Ebola infection of humans is a biological mistake, said Robert Garry Jr., an Ebola researcher at Tulane University in New Orleans. Killing the host is a poor strategy for a parasite, he explained.
“We’re a dead end for this virus, basically,” Garry said. “And the fact that it has come into humans occasionally shows that it’s not really adapted to us — yet.”
That may or may not be an encouraging thought as public health workers in Western Africa, and now the United States, try to understand what they’re fighting and how to best fight it.
Dr. Thomas Frieden, director of the U.S. Centers for Disease Control and Prevention, emphasized the high stakes this month. “In the 30 years I’ve been working in public health, the only thing like this has been AIDS,” he said.
That epidemic took decades of effort to bring under control, with scientists confronting one mystery after another regarding the virus.
In this 2003 file photo, Scripps Research Institute scientists Dennis Burton, Ian Wilson, and Dan Calarese, left to right, stand behind a computer monitor displaying a rendition of the structure of a possible new AIDS antibody the group has identified.
Dan TrevanIn this 2003 file photo, Scripps Research Institute scientists Dennis Burton, Ian Wilson, and Dan Calarese, left to right, stand behind a computer monitor displaying a rendition of the structure of a possible new AIDS antibody the group has identified.
Likewise, researchers today face some major uncertainties about Ebola.
It’s unknown how two nurses at Dallas Presbyterian Hospital who cared for now-deceased Ebola patient Thomas Eric Duncan — Nancy Pham and Amber Vinson — contracted the disease. No breach in safety standards has been identified.
And a fundamental assumption of Ebola care, that those suspected of having the disease should be watched for 21 days, may be too conservative, according to a paper published Oct. 14 in the journal PLOS Current Outbreaks.