South Sudan, the world's newest country and one of its most troubled, may be home to the world's newest disease. The World Health Organization says it is closely tracking an outbreak of a mysterious hemorrhagic fever that has killed at least 10 people in the country this year and sickened dozens of others. The disease causes Ebola-like symptoms, including bleeding, fever, and fatigue, NPR reports, but the WHO says that, unlike with Ebola, the symptoms quickly disappear when patients receive effective treatment—which can be hard to find in a country shattered by years of brutal civil war. The disease doesn't seem to spread from person to person, though investigators aren't sure exactly how it is transmitted.
The WHO says samples from 33 patients have tested negative for diseases such as Ebola, yellow fever, Rift Valley fever, the West Nile virus, and Zika. Five people did test positive for the mosquito-borne virus, though that would not explain the symptoms—or the deaths. "If I had to guess, I would think an undiagnosed mosquito- or tick-borne viral illness" was behind the outbreak, a UCSF infectious diseases expert tells NPR. He says that while the disease and others like it cause a lot of bleeding, the cause of death tends to be "multi-organ failure—especially the kidneys and liver—and shock syndrome from low blood pressure in patients with severe illness." (Researchers say Zika vaccinations could soon be routine in the US.)