Yesterday, on January 14, Liberia was declared Ebola-free by the World Health Organization (WHO), an announcement that would mean the West African outbreak, the worst in history, is finally over. If you have déjà vu, that’s because this was the third time that the country has been declared free of Ebola virus transmission. Once again demonstrating that these declarations are by no means the end, a case has just been confirmed in neighboring Sierra Leone.

As reported by BBC News, the patient was a man who unfortunately died of the disease earlier this week in the Tonkolili district, northern Sierra Leone, which he had traveled to from near the Guinean border, the third major country to be ravaged by the outbreak. Following a positive diagnosis, officials from Sierra Leone made the announcement just hours after that made by the WHO yesterday. This comes just over two months after the country was declared free of disease transmission.

Efforts are now being made to track down anyone who has been in contact with the man. Those identified will likely be placed in quarantine as a preventive measure to prevent further transmission. Ebola is an infectious disease, but it is not spread through the air or water and requires contact with blood or other bodily fluids. Studies have also shown it can linger in semen for months, offering another potential route of transmission.

At this stage, it’s not clear how this man may have contracted the virus, but even during yesterday’s announcement the WHO warned that flare-ups were still likely. That’s because the virus can persist in survivors even after they have recovered. In addition, some remote communities may have cases that have not been reported to health officials. Countries must therefore stay vigilant and continue monitoring efforts to reduce the likelihood of further outbreaks.