At least nine new cases of Ebola have been reported in West Africa in recent weeks, reviving fears of another deadly outbreak more than two years after the hemorrhagic fever began killing thousands in the region.
The latest case was recorded in Liberia's capital Monrovia. A sick woman was transported from a clinic in the nearby city of Paynesville to Monrovia's Redemption Hospital, the epicenter of the 2014 outbreak in the country. Health officials announced on Friday that the woman, who was said to be in her early 30s, died the previous day.
"She died on arrival and a swab was taken, analyzed in the lab, and confirmed," Tolbert Nyenswah, Liberia's assistant health minister, told the Associated Press. "We are investigating the source."
It's the first new Ebola infection in the country since January, when the World Health Organization (WHO) declared that the outbreak, which killed more than 4,800 people in Liberia alone, was officially over.
Ebola first appeared in West Africa in December 2013, when a 2-year-old boy contracted the virus in the village of Meliandou in Guinea's forest region. The disease spread through the village, and authorities officially declared an outbreak in March after it spread into neighboring Liberia and Sierra Leone, eventually killing more than 10,000 people. Transmissions came to halt last May in Liberia after the country went 42 consecutive days without a new case. Sierra Leone and Guinea followed suit later in the year.
New research has revealed that Ebola may remain in the body for up to nine months after an infected person appears to have recovered. This new timeline is a dramatic increase from previous estimates of 90 days, and semen is believed to be the most common route for reinfection.
WHO has stressed the need to keep certain precautionary measures in place to prevent another large outbreak, including heightened border surveillance, protective gear for healthcare workers, and quarantine procedures for suspected Ebola patients at medical facilities.
"Additional flare-ups of the disease are expected in the months to come, largely due to virus persistence in some survivors," WHO said in a statement on Friday. "The three countries must remain on high alert and ready to respond."
The organization plans to keep 1,000 members of its staff in the region to assist in anti-Ebola efforts.
Watch the VICE News documentary The Fight Against Ebola:
The UN's health agency downgraded the threat level of the outbreak on Thursday, but while it is no longer considered a "public health emergency of international concern," new clusters of infections continue to emerge. At least four people died of Ebola last month in Guinea, and more than 1,000 people who may have come in contact with the infected individuals have been put under quarantine. Liberia shut its border with Guinea, and health officials are trying to determine if the latest flare-ups are connected.
Expedited vaccine development is proving to be a key tool in preventing the virus from spreading out of control again. In Guinea, for example, WHO said on Friday that it had administered VSV-EBOV, a new Ebola vaccine, to hundreds of people in the southern prefectures where flare-ups have occurred.
"The VSV-EBOV vaccine currently being administered was found to be highly effective in preventing Ebola infection in a large trial conducted by Guinea's Ministry of Health, WHO and partner agencies last year," the organization explained in a statement. "The 'ring vaccination' strategy involves vaccinating anyone who has come into contact with a person infected with Ebola, as well as contacts of theirs."
The ring vaccination approach has been used in Guinea and Sierra Leone, but no plans have been announced yet for Liberia.
While several drugs and vaccines have been in development since the first Ebola outbreak in 1976, most of them were tucked away on a shelf or in funding limbo when the virus began wreaking havoc across West Africa in 2013. Public health officials have repeatedly blamed the profit-driven pharmaceutical industry for the fact that an anti-Ebola drug had never been approved. As the outbreak escalated, WHO pushed for fast-track development of the treatments and vaccines in progress. The efforts propelled VSV-EBOV into human trials in West Africa last year.
Follow Kayla Ruble on Twitter: @RubleKB