6. HIV/AIDS
The virus that causes AIDS, or acquired immunodeficiency syndrome, known as HIV, was first discovered in 1981 and is thought to have originated in African chimpanzees before being transmitted to humans in the early 20th century.
Since its initial discovery in the Democratic Republic of the Congo in 1976, the illness has gone untreated for many years.
But today, thanks to modern medications, HIV is a much more controllable chronic illness. In fact, the number of individuals dying each year from HIV/AIDS decreased from 2.2 million to 1.6 million globally, and as of early 2020, two people had even been cured of the virus!
