Even as government officials express confidence that researchers know the key facts about Ebola, many questions crucial to preventing an outbreak in the United States remain unanswered, scientists told a workshop at the National Academy's Institute of Medicine in Washington on Monday. Virtually all the unknowns have practical consequences, participants emphasized, making it foolish and perhaps dangerous to base policy on weak science. For instance, virologists believe that Ebola is spread when people come in contact with the virus-laden bodily fluids of those who are already sick and then touch their eyes, nose or mouth, allowing the virus to pass through mucous membranes and enter the bloodstream. But penetration through intact skin has not been definitively ruled out, said hemorrhagic-fever expert Thomas Ksiazek of UTMB, who co-led a session on Ebola's transmission routes