Cara Lynn Shultz is a writer-reporter at PEOPLE. Her work has previously appeared in Billboard and Reader's Digest.

A warning has been issued to travelers over the spread of three diseases, including the Marburg virus. It's a close cousin of Ebola that's been dubbed the "bleeding eye" virus due to one of its symptoms.

Marburg, Mpox and Oropouch (commonly called "sloth fever") are spreading in multiple countries, according to the UK Department of Health's site, Travel Health Pro.

Marburg is a rare but "severe hemorrhagic fever that can cause serious illness and death," the U.S. Centers for Disease Control says, adding that there is no treatment or vaccine for it. But, if detected early, supportive care with rehydration and symptomatic treatment improves survival, according to the Africa CDC.

Initial symptoms, the CDC says, include fever, chills, headaches, a rash with both flat and raised bumps, and sore throat. As the Cleveland Clinic explains, because it's hemorrhagic, it "damages blood vessels and causes bleeding" -- often from the eyes, nose, mouth, or vagina.

There have been 66 illnesses and 15 deaths in Rwanda, according to the CDC, but many more may be infected. The CDC also says there are no known cases outside of Rwanda, and the risk of infection with this virus in the U.S. is low.

Marburg is spread through contact with Egyptian rousette bats, or by contact with infected individuals.

There are two kinds of viruses that spread Mpox, the CDC says: Clade I and Clade II. Clade I is spreading in Africa, Canada, Europe -- and on Nov. 15, the CDC says a case of Mpox was identified in California that was connected to the outbreak in Africa.

Since January, there have been more than 21,000 confirmed cases of both types of Mpox, the CDC says. It's transmitted by close contact with infected individuals, or by contact with contaminated objects.

Oropouch, the CDC says, is spread by "biting midges and some mosquitoes." While most people recover within a month, the CDC says 1 in 20 will develop a more serious disease.

Symptoms include "sensitivity to light, dizziness, pain behind the eyes, nausea, vomiting, and rash," the CDC says, while more serious disease includes meningitis, encephalitis, and bleeding.