FREETOWN, Sierra Leone (AP) — Ebola experts are in Sierra Leone's Kambia district investigating a case that emerged less than a week after the country's last known patient was discharged from a hospital, a World Health Organization spokeswoman said Monday. Experts target contacts of the infected, and contacts of those contacts to create a buffer zone around a case to prevent its spread. The worst Ebola outbreak in history has killed nearly 4,000 people in Sierra Leone and more than 11,300 overall.