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A CONTRIBUTION TO THE EPIDEMIOLOGY OF POLIOMYELITIS IN NEW ZEALAND <By A. W. S. Thompson, 0.8. E., M.8., M.R.C.P., D.P.H., Medical Officer of Health, Auckland) FOREWORD The investigation described in this paper was undertaken in Auckland during the summer of 1947-48. The field-work was carried out by the writer in conjunction with Dr. G. A. de Lautour, Medical Officer of Health, and Miss D. F. Gatenby, Nurse Inspector; .assistance was also given by Drs. Houghton, Miller, and Parr, of the staff of the Auckland Health District. My best thanks are due to all for their ready co-operation and hard work, and for their carefully kept records, which greatly facilitated the task of analysis. In consideration for the reader, most of the tables have been relegated to the Appendix, and full use has been made of graphic methods of presentation of data. A. W. S. Thompson. Auckland, 27th May, 1948. Note. —Unless otherwise stated, all cases of illness are referred to in this paper by date of onset, mot of notification. • CONTENTS PAGE Foreword .. .. .. .. .. .. .. .. .. 61 I. Poliomyelitis Epidemic, 1947-48 .. .. .. .. .. .. 62 11. Network Linking Four Positive Cases .. .. .. .. .. .. 64 111. Plan for an Investigation .. .. .. .. .. .. 66 IV. Reliability of Findings .. .. .. .. .. .. 89 V. The Background of the Epidemic : The Early Stages .. .. .. .. 70 VI. Illnesses in Affected Households .. .. .. .. .. .. 72 VII. The Background : Peak and Decline .. .. .. .. .. .. 79 (а) Incidence in Age and Sex Groups .. .. .. .. 79 (б) Ratio of " Suspect " Illnesses to Positive Cases .. .. .. 80 (c) Leading Symptoms, Positive and Suspect Cases .. .. .. .. 82 VIII. Discussion, and a Suggested Line of Inquiry .. .. .. .. .. 84 IX. Conclusions .. ..... .. .. .. .. .. .. 87 X. Summary .. .. .. .. .. .. .. .. 89 Appendix (Tables Ito VII) .. .. .. .. .. .. 90-92 Figures I. Spot Maps : 5, 10, 20, 50 Cases .. .. .. .. .. 62-63 11. Network Linking Four Positive Cases .. .. .. .. .. .. 65 111. Map Showing Test Areas .. .. .. .. .. .. .. 68 IV. Illnesses Amongst Families Visited in December .. .. .. .. 71 V. Relationship Between Positive Cases and Suspect Illnesses .. .. 73 VI. Development of Suspect Illnesses in Affected Households .. .. .. 75 VII. Inverse Relationship Between Suspect and Positive Cases .. .. .. 76 VIII. Percentage of Age/Sex Groups Not Affected .. .. .. .. .. 77 IX. Intervals Between Successive Illnesses in Same Household .. .. .. 78 X (I). Males—Positive and Suspect Cases Month by Month .. .. .. .. 81 X (II). Females —Positive and Suspect Cases Month by Month .. .. .. .. 81 XI. Percentages in Each Age Group (General Population) Affected .. .. .. 82 XII. Population in Each Age Group, Showing Proportion Affected .. .. .. 83 Tables Tables I to VII will be found in Appendix. VIII. Incidence of Positive Cases in Urban and Rural Districts .. .. .. 80 IX. Ratio of Suspect Illnesses to Positive Cases .. .. .. .. .. 80 X. Leading Symptoms in Positive and Suspect Illnesses .. .. .. 84 XI. Comparison Between Incidence of Threadworms (Peckham) and " Suspect" Illnesses (Auckland) .. .. .. .. .. .. .. .. 85

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