2. Ebola virus
The first known Ebola outbreaks in humans struck at the same time in the Republic of the Sudan and the Democratic Republic of Congo in 1976. As you probably know, Ebola is spread through contact with blood or other body fluids, or tissue from infected people or animals. According to Elke Muhlberger, an Ebola virus expert and associate professor of microbiology at Boston University, the known strains vary dramatically in their deadliness.
However, one strain, Ebola Reston (one of six known viruses within the genus Ebolavirus), doesn’t even make people sick. But for the Bundibugyo strain, the fatality rate is up to 50 percent and it is up to 71 percent for the Sudan strain, according to WHO. The outbreak underway in West Africa began in 2014, and it is known as the largest and most complex outbreak of the disease up until now, according to WHO.