This great epidemic was mainly one of relapsing fever. The patient "got the cool," or passed the crisis of the fever, usually on the evening of the fifth or seventh day, sometimes on the ninth, the evening exacerbation, which was to prove critical, being ushered in generally with a rigor, and passing off in profuse perspiration throughout the night. The five-day fever was more certain to relapse than that of seven days, the seven-day fever was more likely to relapse than that of nine days. The relapses might be one or two or three or more, prolonging the illness for weeks. The clear interval varied from twenty-four hours to fourteen days. There were some cases with jaundice which led Stokes and Graves to speak loosely of "yellow fever[484]." O'Brien saw only four cases with exquisite icterus in fifteen hundred cases of relapsing fever. There was a small proportion of cases of ordinary typhus of a severe kind, marked by unusual delirium or phrensy and the absence of sordes on the teeth or petechiae on the skin; the typhus cases became more numerous in the winter season, or, in other words, the original attack lasted to nine, eleven, or thirteen days, with little or no tendency to relapse. Gangrene was not uncommon in one part of the body or another, and in four cases the feet became gangrenous[485].
Even with the admixture of pure typhus cases, and with dysenteric complications in the autumn and winter, the mortality of the whole epidemic was small--not more than it would have been among a third part the number of fever cases in an ordinary year. At the Cork Street Hospital alone (including the tents) there were 8453 admissions from 4th August, 1826, to 4th April, 1827, with 332 deaths, or four deaths in a hundred cases. The proportion of recoveries was quite as remarkable in known instances in the squalid homes of the poor, where two or three would be found ill of fever on one pallet, or a father and six children in one room, shunned by the neighbours.
The strangest thing in this epidemic was the sequel of it. In the spring of 1827, intermittent fever, which had not made its appearance for several years in Dublin, began to prevail pretty generally; whilst the ordinary continued fever showed a strong tendency to assume the intermittent and remittent forms. It is not surprising, therefore, that Dr O'Brien, who had these varied experiences of epidemic dysentery in 1825, of epidemic relapsing fever and typhus in 1826, and of intermittent fever in 1827, should adopt Sydenham's language of epidemic constitutions, and revert to the old Sydenhamian doctrine of causes. While the sequence of epidemic diseases in Dublin was some dysentery in the autumn and winter of 1825 and relapsing fever on a vast scale during the excessively dry spring and summer of 1826, in country districts of Ireland, such as Skibbereen, dysentery became epidemic after the great drought and heat of 1826, while "fever disappeared altogether," and indeed all other prevalent forms of sickness gave way before it, so general was it. Such is the report from Skibbereen, county Cork, a district that became early notorious, in the great famine of 1846-47, and was perhaps a kind of barometer of Irish distress twenty years earlier. The epidemic dysentery of 1826 attacked all classes there, but chiefly the poorest; it was apt to begin insidiously, and, as it was often neglected, so it often became obstinate and hard to cure. Dr McCarthy attributed it to the drought of 1826, the commercial distress of 1825, the lack of employment for labourers, the overgrowth of population, and the alarming rise in the prices of food[486]. He uses the same economic illustrations as O'Connell and Smith O'Brien in the Great Famine twenty years after, which were, indeed, as old as the time of Bishop Berkeley[487].