(NEW YORK) -- The World Health Organization is investigating a mysterious illness in South Sudan that has killed dozens of people.
So far, 97 people have died of the unknown disease in Fangak, Jonglei State, in the northern part of the country.
Fangak County Commissioner Biel Boutros Biel told ABC News on Thursday that the latest fatality occurred in an elderly woman.
Deaths have mostly been reported among the elderly and children ages 1 to 14, according to a statement from South Sudan’s Ministry of Health.
The symptoms of the mysterious illness include cough, diarrhea, fever, headache, chest pain, joint pain, loss of appetite and body weakness, officials said.
Biel said the WHO team that traveled to Fangak has since left, but did not communicate their findings to local officials.
In a statement to ABC News, Collins Boakye-Agyemang, a spokesperson for WHO Africa, said the agency began investigating the outbreak in November but did not provide further details.
According to BBC News, because the area has recently been hit with heavy floods, the WHO tested samples from patients for cholera, which is typically contracted from infected water supplies.
However, the samples returned negative for the infectious bacterial disease, the outlet reported.
Sheila Baya, a lecturer in the College of Medicine at University of Juba in South Sudan, told BBC News that WHO scientists had to reach Fangak by helicopter due to the flooding to conduct testing.
Biel told ABC News that some nongovernmental organizations have delivered medical supplies to Fangak and are in the process of setting up mobile clinics to help treat people.
In a statement last month, international humanitarian group Médecins Sans Frontières (Doctors Without Borders) called the floods a “perfect storm” for disease outbreaks.
"People do not have enough water or options for water storage, and there is no garbage collection, while dead goats and dogs are left rotting in the drainage systems," the statement read. "With the conditions further worsened by the influx of new arrivals [at camps], people are at higher risk of outbreaks and waterborne diseases such as acute watery diarrhea, cholera and malaria."
ABC News’ Morgan Winsor contributed to this report.