The mystery illness that has been sickening mainly malnourished children in the Democratic Republic of Congo (DRC) has been identified as Malaria. This flu-like illness is a serious disease caused by a parasite that infects a certain type of mosquito.

The disease has sickened nearly 600 people, mostly children, and killed 143 and was dubbed “disease X” for a short time before health officials declared it to be a severe form of Malaria.

Reuters reports that on Tuesday the DRC’s health ministry said that a previously unidentified disease, sometimes labeled “Disease X” in the media, found in the country’s Panzi health zone in the southwestern Kwango province, is a serious form of malaria. “The mystery has finally been solved. It’s a case of severe malaria in the form of a respiratory illness,” the health ministry stated.

Malaria is endemic in the DRC. The parasite Plasmodium is transmitted to humans primarily through the bites of infected mosquitoes. People who have malaria usually feel very sick with a high fever and shaking chills. The main symptoms reported in this particular outbreak are similar to those of influenza, with patients suffering from headaches, coughing, and shortness of breath. “Difficulty breathing” is included as a common respiratory symptom in severe cases of malaria, according to the World Health Organization. Doctors are also seeing patients with acute anemia, which can accompany malarial disease. -Forbes

The concern over this illness had been that the previously “unknown” illness was perhaps a novel or mutated respiratory viral disease of some sort that could be transmitted from human to human. But identifying malaria as the culprit should at the very least, dispel some fears of a wider epidemic.

Malaria’s mode of transmission, through mosquito bites, limits its ability to spread rapidly and widely compared to airborne viruses.

According to the Centers for Disease Control and Prevention, Malaria symptoms range from very mild to severe disease and even death. Travelers with symptoms of malaria should see a healthcare provider as soon as possible, even if still traveling.

Some people are at higher risk of having serious malaria-related problems if they get sick. Malaria is a curable disease if diagnosed and treated quickly and correctly, the CDC said.