For now, only symptoms can be treated in hopes of keeping people strong enough that their immune systems can catch up. But in the past five years, several experimental vaccines and treatments have been effective in other primates, said virologist Alexander Bukreyev of the University of Texas Medical Branch in Galveston, and he estimates that something could be approved for human use within five years. Why is Ebola so deadly? Ebola punches holes in blood vessels, causing massive bleeding and shock. It does this by killing endothelial cells, which form the blood vessels’ lining and other partitions in the body. When those cells die, blood and other fluids can leak into other organs and body parts.The virus replicates very quickly, before most people’s bodies can mount a counterattack. People often have massive bleeding seven to 10 days after infection. It effectively disables the immune system by breaking down the development of antibodies. Scientists are not certain exactly how. The virus is often spread to humans via the contaminated meat of monkeys and other animals. It spreads from human to human through contact with body fluids. Sources: Steve Monroe, deputy director of the National Center for Emerging and Zoonotic Infectious Diseases; World Health Organization BY BONNIE BERKOWITZ, DARLA CAMERON, ANNIE DANIEL, LARIS KARKLIS AND TODD LINDEMAN/THE WASHINGTON POST The deadliest strain F. A. Murphy of University of Texas Medical Branch The Zaire strain has been the most common and deadliest in humans. Fifteen outbreaks, including the first one in 1976 and this year’s, are attributable to that species of the virus. A 2003 Zaire outbreak in Congo killed 90 percent of the people infected. Locations of outbreaks since 1976 Current outbreak What can be done? How does it spread? Number of cases and types of outbreaks since 1976

Published Aug. 1, 2014.