There were celebrations in Sierra Leone Saturday as the World Health Organization declared the country free of Ebola transmissions – but it remains under heightened surveillance for a further 90 days.

Nearly 4,000 people have died in Sierra Leone in the worst Ebola outbreak in history.

Weak leadership, shoddy supplies and infighting worsened the battle against this outbreak of the virus that has killed some 11,000 people mainly in Guinea, Sierra Leone and Liberia, and WHO has been criticized for its response.

Sierra Leone's health officials checking for Ebola in this March 2015 photo. ZOOM DOSSO / AFP - Getty Images

“Since Sierra Leone recorded the first Ebola case in May 2014, a total number of 8,704 people were infected and 3,589 have died, 221 of them healthcare workers, all of whom we remember on this day” said Dr Anders Nordström, WHO Representative in Sierra Leone, in a statement.

The organization said that 42 days have passed — twice the maximum incubation period — since the last confirmed Ebola patient was discharged Sept. 25.

WHO has recorded seven new cases in neighboring Guinea in the past 21 days.

In the capital Freetown, people were seen dancing and singing into the early hours of Saturday ahead of the WHO announcement.