 Contemporary accounts suggest cases of plague occurred through the winter of 1664/5, some of which were fatal but a number of which did not display the virulence of the later epidemic.The winter was cold, the ground frozen from December to March, river traffic on the Thames twice blocked by ice, and it may be that the cold weather held back its spread.This outbreak of bubonic plague in England is thought to have spread from the Netherlands, where the disease had been occurring intermittently since 1599.