The World Health Organization on Saturday declared Sierra Leone free of Ebola virus transmission. The announcement marked 42 days (two 21-day incubation periods) since the release of the last known Ebola patient from a Sierra Leone treatment unit. The Centers for Disease Control and Prevention said U.S. government partners will continue to help the country assist survivors and rebuild its public health infrastructure. “With the support of CDC and many other partners, Sierra Leone has a stronger disease surveillance and response system in place for suspected Ebola cases, and the country remains vigilant in its efforts to stay at zero cases,” CDC said.