On the far left-hand side, that bar represents a group of people who are uninfected, and as we move towards the right-hand side, these people have become infected and they're moving towards the stage that they're infectious.
Di bagian paling kiri, batang itu mewakili kelompok orang yang tidak terinfeksi, dan saat kita terus bergerak ke sebelah kanan, orang-orang ini telah terinfeksi dan bergerak ke tahap menular.