If you want to know about geometric expansion, try this old parable. Take a chess board (64 squares) put ONE grain of rice on the first square. On each additional square put TWO times the previous amount. 1, 2, 4 etc. You will find that by the time you got to the end there would not be enough rice in the world to fill the last square. By about 18 squares you are at over 1 Million grains. The same is true of virulent infections. 2, 4, 8, 16, 32, 64, 128, 256, 512, 1000+, 2000+, 4000+, 8000+, 16,000+ etc. doesn't take long. That's ONE infected person infecting just ONE other person.