Several factors are contributing to the slowing of the outbreak. The virus never went airborne, to the huge relief of health officials. And it turns out that patients are most likely to infect others late in their infection, rather than early. As a result, identifying and isolating infected persons quickly and then tracking down and testing persons with whom they have been in contact has been the key to containment. Getting people to change cultural practices, such as kissing and shaking hands as greetings and washing the dead prior to burial, has slowed the spread of the disease as well.
Nevertheless, it's still too soon to declare the outbreak over. It takes a lot of manpower to find and test all the persons who may have been exposed to someone with the disease, and the three countries with the most cases lack those kinds of resources. Nearly half of all new cases are identified only post-mortem (after death), which makes containment and tracking of exposed persons more difficult.
There are still no cures or effective preventative vaccines for Ebola. Let's hope we can continue to keep this outbreak contained until cures are available.