The disease is new to West Africa, and has been flaring up intermittently for nearly five months, frustrating health care officials. Moreover, local customs encourage family members to care for the sick and personally prepare the deceased for burial, further increasing the chances of transmission. Many also express scepticism towards Western medicine, and are not particularly welcoming of doctors decked out in protective regalia, including full body suits and gloves.
In truth, there's a lot we don't know about Ebola and its effects. Quarantine methods are effective in curbing its spread, in part because its mortality rate is so high - an infected person may not live long enough to pass on the virus to many other people. Let's hope that the outbreak is contained soon, and that in the meantime we don't succumb to what some are calling an "epidemic of fear".
Update: The Economist has a very informative graphic about the outbreak here.