On Friday, the World Health Organization (WHO), which is an United Nations health agency, has informed they were conducting an investigation into an unknown disease that had already killed three people in Johannesburg, South Africa.

The mysterious disease, which might be related to the Ebola virus, seems to be a form of hemorrhagic fever, a condition that spreads very rapidly and leads, in most cases, to shock and death.

So far, WHO have performed test for Ebola, Lassa fever, Rift Valley fever, Marburg fever and various other types of hemorrhagic fever, all of which have been negative.

The health agency has also revealed that the first person to have died from the disease on September 13 (a female tour guide) had become sick while in Zambia and she had afterwards been evacuated to South Africa.

The other two people who were killed by the unknown virus were a paramedic and a nurse, both of whom had treated the aforementioned tour guide. They died on September 30 and October 4, respectively.

The World Health Organization has stated that more than one hundred people were then under medical supervision, adding that they expected further test results on Sunday.

Viral hemorrhagic fevers are a group of diseases caused by five families of Ribonucleic Acid (RNA) viruses: the Arenaviridae, Filoviridae, Bunyaviridae, Togaviridae, and Flaviviridae, the medical condition’s symptoms including fever and bleeding disorders.