Table 4. Numbers of all medical institutions, standard numbers of SMIs, and numbers of SMIs needed for estimating prefectural influenza incidence: internal medicine clinics with a secondary pediatric practice.
| Prefecture | No. of all medical institutions |
Standard no. of SMIs |
No. of SMIs needed for estimating influenza incidence in prefecturesa | |||
| Critical proportion of influenza epidemic cases | ||||||
| 25% | 50% | 75% | 90% | |||
| Hokkaido | 428 | 17 (4.0) | 17 (4.0) | 17 (4.0) | 17 (4.0) | 17 (4.0) |
| Aomori | 183 | 7 (3.8) | 12 (6.6) | 17 (9.3) | 21 (11.5) | 29 (15.8) |
| Iwate | 81 | 3 (3.7) | 5 (6.2) | 7 (8.6) | 9 (11.1) | 13 (16.0) |
| Miyagi | 229 | 9 (3.9) | 9 (3.9) | 13 (5.7) | 16 (7.0) | 22 (9.6) |
| Akita | 94 | 4 (4.3) | 7 (7.4) | 9 (9.6) | 12 (12.8) | 16 (17.0) |
| Yamagata | 106 | 3 (2.8) | 7 (6.6) | 10 (9.4) | 13 (12.3) | 17 (16.0) |
| Fukushima | 297 | 9 (3.0) | 11 (3.7) | 17 (5.7) | 20 (6.7) | 29 (9.8) |
| Ibaraki | 348 | 13 (3.7) | 13 (3.7) | 16 (4.6) | 21 (6.0) | 30 (8.6) |
| Tochigi | 269 | 9 (3.3) | 13 (4.8) | 18 (6.7) | 22 (8.2) | 31 (11.5) |
| Gunma | 295 | 9 (3.1) | 11 (3.7) | 16 (5.4) | 19 (6.4) | 27 (9.2) |
| Saitama | 746 | 29 (3.9) | 29 (3.9) | 29 (3.9) | 29 (3.9) | 29 (3.9) |
| Chiba | 607 | 24 (4.0) | 24 (4.0) | 24 (4.0) | 24 (4.0) | 27 (4.4) |
| Tokyo | 1718 | 41 (2.4) | 41 (2.4) | 41 (2.4) | 41 (2.4) | 41 (2.4) |
| Kanagawa | 731 | 31 (4.2) | 31 (4.2) | 31 (4.2) | 31 (4.2) | 31 (4.2) |
| Niigata | 227 | 8 (3.5) | 8 (3.5) | 12 (5.3) | 15 (6.6) | 20 (8.8) |
| Toyama | 105 | 3 (2.9) | 7 (6.7) | 10 (9.5) | 13 (12.4) | 17 (16.2) |
| Ishikawa | 88 | 3 (3.4) | 6 (6.8) | 8 (9.1) | 11 (12.5) | 14 (15.9) |
| Fukui | 124 | 4 (3.2) | 12 (9.7) | 17 (13.7) | 21 (16.9) | 29 (23.4) |
| Yamanashi | 137 | 5 (3.6) | 14 (10.2) | 19 (13.9) | 23 (16.8) | 31 (22.6) |
| Nagano | 323 | 11 (3.4) | 13 (4.0) | 18 (5.6) | 22 (6.8) | 32 (9.9) |
| Gifu | 436 | 14 (3.2) | 18 (4.1) | 24 (5.5) | 32 (7.3) | 40 (9.2) |
| Shizuoka | 323 | 11 (3.4) | 11 (3.4) | 12 (3.7) | 16 (5.0) | 21 (6.5) |
| Aichi | 1110 | 43 (3.9) | 43 (3.9) | 43 (3.9) | 43 (3.9) | 43 (3.9) |
| Mie | 242 | 7 (2.9) | 10 (4.1) | 15 (6.2) | 19 (7.9) | 26 (10.7) |
| Shiga | 206 | 7 (3.4) | 13 (6.3) | 17 (8.3) | 22 (10.7) | 30 (14.6) |
| Kyoto | 356 | 12 (3.4) | 12 (3.4) | 14 (3.9) | 19 (5.3) | 25 (7.0) |
| Osaka | 970 | 31 (3.2) | 31 (3.2) | 31 (3.2) | 31 (3.2) | 31 (3.2) |
| Hyogo | 571 | 18 (3.2) | 18 (3.2) | 18 (3.2) | 18 (3.2) | 21 (3.7) |
| Nara | 186 | 6 (3.2) | 12 (6.5) | 17 (9.1) | 20 (10.8) | 28 (15.1) |
| Wakayama | 163 | 4 (2.5) | 9 (5.5) | 13 (8.0) | 17 (10.4) | 22 (13.5) |
| Tottori | 102 | 3 (2.9) | 11 (10.8) | 16 (15.7) | 20 (19.6) | 26 (25.5) |
| Shimane | 155 | 4 (2.6) | 13 (8.4) | 18 (11.6) | 22 (14.2) | 30 (19.4) |
| Okayama | 353 | 9 (2.5) | 14 (4.0) | 20 (5.7) | 25 (7.1) | 35 (9.9) |
| Hiroshima | 296 | 9 (3.0) | 9 (3.0) | 11 (3.7) | 14 (4.7) | 19 (6.4) |
| Yamaguchi | 136 | 4 (2.9) | 7 (5.1) | 9 (6.6) | 12 (8.8) | 16 (11.8) |
| Tokushima | 184 | 4 (2.2) | 14 (7.6) | 19 (10.3) | 23 (12.5) | 32 (17.4) |
| Kagawa | 88 | 3 (3.4) | 7 (8.0) | 10 (11.4) | 13 (14.8) | 17 (19.3) |
| Ehime | 110 | 4 (3.6) | 6 (5.5) | 8 (7.3) | 10 (9.1) | 14 (12.7) |
| Kouchi | 68 | 3 (4.4) | 6 (8.8) | 8 (11.8) | 11 (16.2) | 14 (20.6) |
| Fukuoka | 477 | 15 (3.1) | 15 (3.1) | 15 (3.1) | 15 (3.1) | 19 (4.0) |
| Saga | 124 | 4 (3.2) | 10 (8.1) | 14 (11.3) | 17 (13.7) | 24 (19.4) |
| Nagasaki | 166 | 5 (3.0) | 8 (4.8) | 11 (6.6) | 14 (8.4) | 19 (11.4) |
| Kumamoto | 241 | 8 (3.3) | 9 (3.7) | 14 (5.8) | 18 (7.5) | 23 (9.5) |
| Oita | 124 | 4 (3.2) | 8 (6.5) | 10 (8.1) | 14 (11.3) | 18 (14.5) |
| Miyazaki | 92 | 3 (3.3) | 6 (6.5) | 8 (8.7) | 11 (12.0) | 14 (15.2) |
| Kagoshima | 215 | 7 (3.3) | 9 (4.2) | 13 (6.0) | 17 (7.9) | 23 (10.7) |
| Okinawa | 140 | 6 (4.3) | 10 (7.1) | 13 (9.3) | 17 (12.1) | 23 (16.4) |
| Totals | 14 770 | 490 (3.3) | 629 (4.3) | 770 (5.2) | 910 (6.2) | 1155 (7.8) |
SMI: sentinel medical institution.
Percentages of all medical institutions are in parentheses.
aNumbers of SMIs for estimating influenza incidences in prefectures were calculated with the assumption that the standard error rate of the incidence estimate for a given critical proportion (25%, 50%, 75%, or 90%) of influenza epidemic cases was less than 10%.