20th Century (1 ene 1901 año – 31 dic 2000 año)

Descripción:

- Conjoined (Siamese) twins were separated successfully for the first time in 1953

- Acquired immune deficiency syndrome (AIDS) was identified as a disease in 1981

- Walter Reed demonstrated that mosquitoes carry yellow fever in 1900

- The human imunodeficency virus (HIV) causing AIDS was identified in 1984

Average life span was 60 to 80 years