Their scarcity resulted in malnutrition, which increases susceptibility to infections due to weakened immune systems. In the autumn of 1314, heavy rains began to fall, which were the start of several years of cold and wet winters. The already weak harvests of the north suffered and the seven-year famine ensued. In the years 1315 to 1317 a catastrophic famine, known as the Great Famine, struck much of North West Europe. It was arguably the worst in European history, perhaps reducing the population by more than 10%.