 -- Liberian officials confirmed that Ebola has returned to the country after the death of a teenager.

The 17-year-old boy tested positive for the virus 48 days after the World Health Organization declared Liberia free of Ebola on May 9. More than 8,000 people died from the disease after the virus spread across the country in 2014.

While officials only confirmed the virus after the teenager had died, he was buried according to Ebola protocols to reduce risk of infection, according to the Liberian government.

“Although this was not the situation we were hoping for, this incident demonstrates[s] that our alert systems are working,” Liberia’s Minister of Health Dr. Bernice Dhan said in a statement. “The structures we have in place to strengthen our surveillance systems in Liberia allowed us to respond quickly. It is critical that the Liberian people remain vigilant and continue all prevention measures to stop the spread of Ebola.”

Contact tracing used to identify anyone else potentially exposed has already begun, according to the Associated Press. Government officials said the cause for the initial infection remains unknown. Dhan asked those exposed to be cooperative about quarantine and for others to speak up if they have symptoms.

“We cannot do this without the participation and support of the communities,” Dhan said on Tuesday at the a press conference.

Dr. William Schaffner, an infectious disease expert at Vanderbilt University Medical School, said it’s not surprising an Ebola case reappeared in Liberia.

“We have continuing smoldering Ebola in Guinea and Sierra Leone and it is likely once this investigation is completed there may be association with travel to those countries,” said Schaffner, who is not investigating this case.

“The good thing is this [infection] occurred in a rural village and appears to have been diagnosed rather promptly and appropriate public health responses were put into place,” he said.

Schaffner said it appears the government have taken quick and clear steps that should stop the virus from turning into an outbreak similar to the one that started last year.