A mysterious illness that is ravaging South Sudan is currently being investigated by the World Health Organization, ABC News reports.

Officials said symptoms of the illness include cough, diarrhea, fever, headache, chest pain, joint pain, loss of appetite, and body weakness. To date, 97 people have died of the unknown disease in Fangak, Jonglei State, in the northern part of the country.

According to a statement from South Sudan’s Ministry of Health, fatalities have mostly been reported among the elderly and children ages 1 to 14. Biel Boutros Biel, Fangak County Commissioner told ABC News on Thursday that the latest death was an elderly woman.

Collins Boakye-Agyemang, a spokesperson for WHO Africa, issued a statement saying that the agency has been investigating the outbreak since November but did not disclose any more details.

The BBC News reported that the area was subjected to heavy floods and the WHO tested samples from patients for cholera, which is typically contracted from infected water supplies. After testing, all samples came back negative.

Biel noted that some nongovernmental organizations have delivered medical supplies to Fangak and they are currently setting up mobile clinics to help treat people who have contracted the deadly disease

In a statement back in November, Médecins Sans Frontières (Doctors Without Borders), an international humanitarian group, described the floods as 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 refuge camps], people are at higher risk of outbreaks and waterborne diseases such as acute watery diarrhea, cholera, and malaria."