FREETOWN, Sierra Leone (AP) -- The World Health Organization declared Sierra Leone free from Ebola transmissions on Saturday, as West Africa battles to stamp out the deadly virus that is holding on in neighboring Guinea.
Nearly 4,000 people have died in Sierra Leone of Ebola since the outbreak began in late 2013. The organization said 42 days have passed since the last confirmed Ebola patient was discharged on Sept. 25 after two consecutive negative test results.
Hundreds of people cheered in the capital Saturday as Dr. Anders Nordstrom, Sierra Leone representative for the World Health Organization, declared the end of the Ebola outbreak in Sierra Leone.
"WHO commends the government and people of Sierra Leone for the significant achievement of ending this Ebola outbreak," he said.
A country must go 42 days --- equal to two incubation periods of 21 days --- without an Ebola case in order for WHO to declare it free of Ebola transmission. It's a benchmark that neighboring Liberia reached in May only to then experience a brief reappearance of cases before it was declared free from transmissions again in September.
Sierra Leone had at one point begun the 42 day countdown only to discover a new Ebola case. Guinea, where the epidemic began, now remains the only country struggling to rid itself of the disease. WHO has recorded seven new cases in neighboring Guinea in the past 21 days.
Sierra Leone now enters a 90-day intensive surveillance period.
"This new phase is crucial as our goal is to ensure a resilient zero and that we can detect and respond to any potential flare-ups," said Nordstrom, adding that WHO will maintain staff in Sierra Leone.
Authorities caution that vigilance must continue.
"Until the entire West African region records zero cases and Sierra Leone continues with heightened vigilance beyond 42 days, and beyond 90 days, then and only then the region can think of true recovery," said Alfred Palo Conteh, Chief Executive Officer of Sierra Leone's National Ebola Response Centre.
The United States government congratulated the government and people of Sierra Leone in a statement from the embassy.
"Ending the current outbreak is a moment for celebration, but also reflection," it said. "Experience has shown that where Ebola has occurred, it will resurface. So the United States resolves to remain vigilant and urges others to do likewise."
Weak leadership, shoddy supplies and infighting worsened the battle against the current Ebola outbreak that has killed some 11,000 people mainly in Guinea, Sierra Leone and Liberia, and WHO has been criticized for its response.