Course of the Famine, 1845-1850:
1845: Farmers noticed their potatoes were turning black with a smell. They brushed it off because they had many potatoes in storage.
1846: Two thirds of potatoes were lost to the blight, the potatoes in storage was used up. Disease such as measles and tuberculosis spread rapidly.
1847: The potato fungus was mostly gone, however there were very few potato seeds to grow, leading to a shortage.
1848-50: Starvation and disease worsened, even though there were very few potatoes. Roughly 50k people more died than in 1846.