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Uncertainties About Ebola Transmission Loom Large, U.S. Scientists Warn

Nov. 4, 2014 (EIRNS)—At a workshop at the National Academy’s Institute of Medicine, held in Washington, D.C., on Nov. 3, a number of scientists warned that there are many unanswered questions about Ebola’s transmission that are crucial to preventing an outbreak of the virus in the U.S., Reuters reported today.

Arguing that it is foolish, and even dangerous, to base policy on "weak science," a number of the speakers warned that all of the unknowns have practical consequences. Virologists, for example, believe the virus is spread when people come in contact with bodily fluids of infected individuals, and then touch eyes, nose or mouth, allowing the virus to pass through mucous membranes into the bloodstream. But Thomas Ksiarek, a hemorrhagic-fever expert at the University of Texas Medical Branch, (UTMB), who co-led a session on Ebola transmission routes, says that penetration through intact skin hasn’t been definitively ruled out. One question to be answered, he said, is "whether bleach or hand sanitizer," which are being widely used in West Africa to protect people from Ebola, "make the skin more susceptible" to being penetrated by the virus. "It’s a question that has to be asked."

Another crucial question is whether the virus can be spread by people who show no symptoms. Dr. Andrew Pavia, chief of pediatric infectious disease at the University of Utah, said that such "sub-clinical transmission" very much remains open to question. Nor do experts know whether the infectious dose of virus depends on how it enters the body, Pavia said. Another unknown is whether the time between exposure to Ebola and the appearance of symptoms depends on which bodily fluids someone contacted. If it does, then someone exposed through saliva, rather than blood, might incubate the virus for longer than the 21 days that officials insist is the limit of the incubation period.

Dr. C.J. Peters, a UTMB field virologist, noted that 21 days was the longest incubation time during the 1976 Ebola outbreak. But, he added, "I would guess that 5% of people" can transmit the virus after incubating it for more than three weeks.