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Expert Says Airborne Ebola Transmission Is Not Impossible

Current death toll exceeds 2,000

The idea of the Ebola virus becoming airborne is not far-fetched, and its ability to enter cells that line the trachea and lungs has been shown under controlled laboratory conditions, a virus expert at Purdue University says.

Dr. David Sanders, who has studied the Zaire strain of Ebola virus that is responsible for the current outbreak in West Africa, says the possibility of the virus becoming airborne should not be discounted.

“It is not unprecedented for a virus to change its mode of transmission,” he says. “Ebola does share some of the characteristics of airborne viruses like influenza, and we should not disregard the possibility of it evolving into something that could be transmitted in this way.”

In a paper published in the Journal of Virology in 2003, a research team led by Sanders and collaborators at the University of Iowa established that the Zaire strain of Ebola virus could enter the epithelial cells that line the human airway. Their experiment used a pseudotyped virus, which was built with the Ebola virus envelope proteins, or outer shell. The inside of the virus was that of a retrovirus to prevent replication of the Ebola virus and to more easily separate the functions of the outer and inner portions of the virus, Sanders says.

“We were studying at the cellular level how the virus enters cells and showed it could enter human airway epithelial cells,” he explains. “However, there are many factors beyond its ability to enter these cells that influence how a virus is transmitted. To be airborne it must be present on tiny droplets from a cough or sneeze and must be able to live outside of the body for a certain length of time. This is not how the virus is currently known to spread, but it is evidence that it has some of the necessary components for respiratory transmission.”

Sanders, who also has expertise in the transmission of viruses from animal to animal and from animals to humans, points to the influenza virus as an example of how a virus can switch from one mode of transmission to another. In birds, its natural host, influenza virus infects the intestinal tract and is transmitted by feces. In mammals, such as humans, it is transmitted. Only a small number of mutations are required to alter the host and mode of transmission, he says.

The death toll from the current Ebola outbreak continues to rise. More than 2,200 deaths have been attributed to the virus, and there are 4,269 probable, confirmed, or suspected cases in Guinea, Liberia, and Sierra Leone, according to the World Health Organization (WHO).

It also appears that the outbreak will continue for several more months, although the estimates vary. WHO believes the outbreak will continue for 9 months, whereas scientists modeling the epidemic for the federal government estimated that it would last 12 to 18 months, the New York Times reported.

In past studies, Sanders found that the Zaire strain of Ebola virus is most similar biochemically to the bird retroviruses, suggesting that it may have at one time been associated with a bird host. His research also uncovered the first step in priming the virus for entry and has important implications for how the virus escapes the body’s adaptive immune system and causes disease.

Source: Purdue University; September 17, 2014.

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