It’s been three years since the Democratic Republic of Congo faced down its last epidemic of Ebola. Now, a case of Ebola has again been confirmed in the country—and public health officials taking the threat seriously.

Starting on April 22, nine people have been stricken with hemorrhagic fever, a group of illnesses that strike multiple systems in the body and that result from a family of viruses that includes Ebola. According to Reuters, three have died from the fever so far, but only one of those cases has been confirmed as Ebola. The World Health Organization has sent specialists to the area, the Associated Press reports.

The new case suggests that Ebola is back in the Democratic Republic of Congo—raising the specter not just of the 2014 outbreak that sickened 66 and killed 49, but the much larger (unrelated) outbreak that swept through West Africa between 2014 and 2016. In the West Africa outbreak, notes the Centers for Disease Control and Prevention, over 28,000 people were infected and 11,325 of them died.

About 50 percent of people who contract Ebola virus disease die from it, writes the WHO, though that number can vary depending on the outbreak. The virus is passed from animals to humans and can spread quickly through a community via contact with an infected person’s broken skin, mucous membranes, and bodily fluids like blood.

As Smithsonian.com reported earlier this year, it’s thought that a small subsection of “superspreaders” are much more likely to transmit the disease than others, but researchers are still learning more about how the disease spreads. Since Ebola incubates so quickly—in as few as two or three days—it’s hard to track who’s spreading it and stop contagion before it stokes an epidemic.

In 2016, a trial vaccine was effective in Guinea, and Reuters reports that 300,000 doses are standing by in case of a widespread outbreak.

Both Congo and public health workers will have to spring into action to prevent a small pocket of disease from turning into a larger outbreak. Hygiene, physical contact and even burial rituals must be carefully monitored among the community to help stave off a spread of the disease, and officials will closely monitor the situation to keep a handle on the situation. A WHO official tells Reuters that since the outbreak is in a very remote area, “we are a little lucky.” Hopefully, that luck will hold and the outbreak will be an isolated one.