(CNN) The Democratic Republic of Congo (DRC) officially declared the end of its 11th Ebola outbreak Wednesday, six months after the first cases of the deadly virus were reported.
"It wasn't easy, but we've done it!" tweeted Dr. Matshidiso Moeti, the World Health Organization's Regional Director for Africa. The WHO made the announcement alongside DRC Minister of Health, Eteni Longondo.
It had been 42 days since the last confirmed case tested negative, according to the WHO. No new confirmed cases have been reported since September 28.
The outbreak began on June 1 in the country's western Equateur Province, just as another outbreak was winding down in the country's east. The eastern outbreak was the world's second-deadliest Ebola outbreak on record, and was officially declared over on June 25 -- but the one in Equateur was just beginning.
By the time the Equateur outbreak ended, it had 130 confirmed cases -- 75 recoveries and 55 deaths.
The two outbreaks were geographically far apart, and genetic sequencing analysis confirmed they were unrelated.
The Equateur outbreak posed a massive logistical challenge for health and aid workers from WHO, local groups, and government agencies. Not only did it come in the middle of the Covid-19 pandemic, when resources were already strained, but the outbreak was located in communities across dense rainforests and remote villages, the WHO said in a press release.
Some places with high levels of infection were only accessible by boat or helicopter, which complicated the transportation and testing of lab samples, and delayed deployment of experts to the affected areas.
Sometimes the workers would also face resistance from the local community, said the WHO. For years, responders on the ground have struggled against extreme community mistrust and fear, worsened by simmering conflict between militant groups and government forces. Some humanitarian workers have come under attack by armed groups.
Health workers tried to counteract this fear by visiting local communities to increase their understanding of the virus. Local health workers and WHO experts visited more than 574,000 households, and vaccinated more than 40,000 people at high risk.
All the while, they had to adhere to Covid-19 restrictions and precautions such as wearing protective gear.
The WHO said it used a new cold chain freezer storage to keep the Ebola vaccine at extremely low temperatures for up to a week, allowing responders to vaccinate people in communities without electricity.
"Overcoming one of the world's most dangerous pathogens in remote and hard to access communities demonstrates what is possible when science and solidarity come together," said Moeti.
"Tackling Ebola in parallel with Covid-19 hasn't been easy, but much of the expertise we've built in one disease is transferable to another and underlines the importance of investing in emergency preparedness and building local capacity."
Ebola first appeared in 1976 in Sudan and the DRC, and gets its name from a river in the latter nation. It is one of the world's most virulent diseases and is transmitted through direct contact with blood or other bodily fluids of infected people.
Ebola causes fever, severe headaches and in some cases hemorrhaging. It spreads through direct contact with bodily fluids or objects contaminated by someone ill with the disease. In some cases, the virus is spread through contact with someone who has died from the disease.
The virus enters the body through broken skin or mucous membranes in the eyes, nose or mouth. It can also spread through sexual contact.
Though the WHO celebrated the end of the Equateur outbreak, it also warned that there's a risk the virus could re-emerge; the virus can persist in survivors' body fluids for months, and is present in animals across the region.
"While the 11th outbreak is over, there is a need for continued vigilance and maintaining strong surveillance as potential flare-ups are possible in the months to come," the organization said in the news release. "The end of this outbreak serves as a reminder that governments and partners must continue to focus attention on other emergencies, even as the fight against Covid-19 persists."