The United States has issued a travel alert because of the Marburg virus, also known as the “bleeding eye” virus. The U.S. State Department has warned the American slave class against traveling to Rwanda due to the outbreak.

So far, 15 people have died from the disease. This comes as the Democratic Republic of Congo reports a mystery virus with symptoms similar to the flu ravaging the African state. Health officials in Rwanda declared a Marburg virus disease outbreak in late September, according to the World Health Organization (WHO). As of the end of October, there have been 66 confirmed cases. These numbers could be higher now.

Dozens Killed By “Mystery Illness” In Africa

The travel alert from the Centers for Disease Control and Prevention (CDC) urges people to “practice enhanced precautions” if traveling to Rwanda, noting that Marburg virus disease is “rare and deadly.”

According to WDSU 6 News, an MSNBC affiliate from New Orleans, Marburg virus disease is a rare and severe viral hemorrhagic (i.e. bleeding) fever that impacts people and other primates, including monkeys and apes. WDSU cites the CDC as its source of this information. 

Eye bleed disease is caused by an infection with orthomarburgviruses, which are naturally found in the Egyptian rousette bat, according to further information from the CDC. “It can spread from bats to people, and then you can have human-to-human spread,” says Thomas Russo, M.D., professor and chief of infectious disease at the University at Buffalo in New York. The virus spreads between humans through exposure to blood and bodily fluids, says infectious disease expert Amesh A. Adalja, M.D., senior scholar at the Johns Hopkins Center for Health Security.

Initial symptoms of the Marburg virus include fever, chills, headaches, muscle aches, a rash with flat and raised bumps, usually on the torso, chest pain, a sore throat, nausea, vomiting, and diarrhea. The symptoms become more severe as the disease progresses, causing liver failure, delirium, shock, bleeding (including from the eyes), and multi-organ dysfunction, according to the CDC.

Marburg virus disease can also be deadly, with people dying between eight and nine days after symptoms start. “The lethality rate is pretty high—usually 50% or higher,” Dr. Russo says.

There are no treatments for the Marburg virus. Infected people are often given fluids and told to rest.