Ebola can only be spread by infected people who show symptoms, the Centers for Disease Control and Prevention said. If an exposed person does not develop symptoms within 21 days of exposure, the person will not become sick with Ebola, according to the CDC.
Contact tracing is the process health workers use to find everyone who comes into direct contact with a sick Ebola patient. If the contact develops a fever or other Ebola symptoms within 21 days of the last day they came into contact with the Ebola patient, the person is isolated and provided care. All of the new patient’s contacts are then found and watched for 21 days.
The CDC warns that even one contact can keep the outbreak going.
Check out below a graphic the CDC prepared to explain how contact tracing works.