Subtitles section Play video Print subtitles [Announcer] The current Ebola outbreak is the largest Ebola outbreak in history and the first ever in West Africa. At CDC, our mission is to prevent, detect, and stop disease outbreaks wherever they occur. And that's why CDC disease detectives are hard at work twenty-four-seven in West Africa. [Raczniak] Hi. Greg, here. I'm with Ishmael, and we're going out with our UN colleagues to train contact tracers. [Announcer] In the fight against Ebola, one of the most important tools we have to prevent spread is contact tracing. [Woman #1: speaking African dialect] [Announcer] In fact, it is the key to stopping the outbreak and saving lives. [Woman #2] She wanted to know how we are going on, anybody who has been sick, anybody who has been hospital. [Announcer] Contact tracing means finding everyone who comes in direct contact with a sick Ebola patient. We ask the Ebola patient or their family who the patient had contact with since they started their symptoms. These contacts are then found and watched for symptoms of sickness for 21 days to see if they become ill. If a contact begins to show symptoms of Ebola, he is immediately isolated, tested and provided care- and the cycle starts again. All of the new patient's contacts must be found and watched for symptoms of sickness for 21 days to see if they become ill. The process is repeated until there are no new patients. [Raczniak] That's how we're gonna stop the transmission chain of Ebola. [Announcer] Contact tracing identifies new Ebola cases quickly so they can be isolated as soon as they show symptoms, preventing spread to others. In the event someone with Ebola travels to another country, we would use contact tracing there as well. The truth is: even one missed contact can keep the outbreak going. But by carefully tracing all contacts and isolating new cases as soon as they develop symptoms, we can prevent further spread. By working together, CDC and its partners will stop the outbreak and save lives from this devastating disease.