This weekend the Ebola virus was the cause of grim headlines after two Americans, including a doctor, were reported to be infected with the disease and Liberia's lead Ebola doctor died from the virus.
That news is on top of the heavy toll of 1,093 infected in the current outbreak as of July 20, according to the World Health Organization. Of those infected, 660 have died, meaning this outbreak has a fatality rate more than 60 percent.
But what exactly is this dangerous disease that kills so many? The Ebola virus is described as a group of viruses that cause a deadly kind of hemorrhagic fever.
The virus is transmitted through contact with blood or secretions from an infected person, either directly or through contaminated needles or medical equipment. The term "hemorrhagic fever" means it causes bleeding inside and outside the body. There is no cure.
The ongoing outbreak has been described as the worst ever Ebola virus outbreak, with infected people in three countries -- Sierra Leone, Liberia and Guinea.
This week officials reported an infected man may have put others at risk after flying on a commercial airliner from Liberia to Nigeria. The WHO has not yet reported any cases of people becoming infected in Nigeria.
The dangerous virus gets its name from the Ebola river in the Democratic Republic of Congo, which was situated near the site of one of the first outbreaks. The virus was first reported in 1976 in two almost simultaneous outbreaks in the Sudan and the Democratic Republic of Congo.
Certain kinds of fruit bats are thought to the be the natural host of the disease, with the initial transmission resulting from a wild animal infecting a human, according to the WHO. Once the disease infects a person it is easily transmissible between people in close contact.
Health workers are particularly at risk for the disease because they work in close contact with infected patients. In this outbreak alone 100 health workers have been infected and 50 of them have died, according to the WHO.
While the current outbreak has been extremely deadly, other outbreaks have seen fatality rates up to 90 percent according to the WHO.
What Is the Ebola Virus?