 Why it can cause such a devastating illness in Africans is not fully understood, but reduced immunity to virus caused by malaria might be to blame.Epstein–Barr virus is important in the history of viruses for being the first virus shown to cause cancer in humans.The second half of the 20th century was the golden age of virus discovery and most of the 2,000 recognised species of animal, plant, and bacterial viruses were discovered during these years.