Poliomyelitis in Northern Ireland—1947, with Special References to Epidemiology

This paper is intended simnply as a record of the more important features of the etidemic of poliomyelitis in Northern Ireland in the summer and autumn of 1947-the worst epidemic yet recorded in this country. INCIDENCE IN PREVIOUS YEARS BEFORE 1947 no large-scale outbreak of poliomyelitis in Northern Ireland was recorded, but available records show that sporadic cases occurred each year since 1923. A table (No. 1) showing the statutory notifications and registered deaths in the years 1937-46 is given, but there are good reasons for believing that the true incidence was much greater than the numbers of statutory notifications. Four of the sixty-seven local authorities in Northern Ireland did not make the disease notifiable until recently; three in 1941, and one in 1948. The figures in the table are, therefore, incomplete, in that about 41,600 of a total population of nearly 1,333,000 are excluded before 1942; and subsequently 5,600 of the population are excluded. More than 25 per cent. of confirmed cases in the recent epidemic were not notified by statutory means, and there is evidence that at least 50 per cent. of cases occurring in the early part of 1947, prior to the epidemic, were not notified. It is probable that similar or even greater percentages of the total number of cases were not notified in previous years,. when the disease was not given comparable publicity. That such difficulties in the notification of this disease are not confined to Northern Ireland is shown by the findings of Nelson and Aycock. They concluded that of 2,263 paralysis cases coming to the Harvard Infantile Paralysis Commission from 1928 to 1941, 23 per cent. were not officially reported; each year reporting was less than 50 per cent. complete for January to May inclusive, but 90 per cent. complete for August, and improved during an epidemic; further, it was most defective in localities of under 2,500 population. Case mortality rates in Table I are unusually high. Average figures for many recorded epidemics vary from 9 per cent. to 15 per cent., and a search revealed extremes of 1.5 per cent. and 33 per cent.; the latter figure (admittedly of little value statistically) being obtained from statistics of an outbreak in Rhodesia involving only nine cases in a small comnmunity of whites. References to the sporadic disease from a statistical point of view are few, and comparable figures for sporadic cases could not …