During the worst year of the Great Irish Famine, ‘Black ’47’, tens of thousands of people fled across the Irish Sea from Ireland to Britain, desperately escaping the starvation and disease plaguing their country. These refugees, crowding unavoidably into the most insalubrious accommodation British towns and cities had to offer, were soon blamed for deadly outbreaks of epidemic typhus which emerged across the country during the first half of 1847. Indeed, they were accused of transporting the pestilence, then raging in Ireland, over with them. Typhus mortality rates in Ireland and Britain soared, and so closely connected with the disease were the Irish in Britain that it was widely referred to as ‘Irish fever’. Much of what we know about this epidemic is based on a handful of studies focusing almost exclusively on major cities along the British west-coast. Moreover, there has been little attempt to understand the legacy of the episode on the Irish in Britain. Taking a national perspective, this article argues that the ‘Irish fever’ epidemic of 1847 spread far beyond the western port of entry, and that the epidemic, by entrenching the association of the Irish with deadly disease, contributed significantly to the difficulties Britain's Irish population faced in the 1850s.