Table 2. Incidence of major influenza virus subtypes endemic to Izu-Oshima Island, Japan, by influenza season.
| Age, y* | Incidence of influenza cases among Izu-Oshima residents, no. (%) |
|||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 2008–09 |
2009–10 |
2010–11 |
Cumulative incidence of A/H1¶ | |||||||||
| No.† | Influenza virus type |
No.† | Influenza virus type A/H1§ | No.† | Influenza virus type |
|||||||
| A‡ | B | A/H1§ | A/H3 | B | ||||||||
| 0–4 | 326 | 65 (19.9) | 11 (3.4) | 323 | 36 (11.1) | 316 | 20 (6.3) | 21 (6.6) | 16 (5.1) | 41 (13.0) | ||
| 5–9 | 366 | 98 (26.8) | 51 (13.9) | 367 | 105 (28.6) | 349 | 39 (11.2) | 6 (1.7) | 91 (26.1) | 137 (39.3) | ||
| 10–14 | 316 | 53 (16.8) | 44 (13.9) | 316 | 97 (30.7) | 332 | 26 (7.8) | 3 (0.9) | 48 (14.5) | 143 (43.1) | ||
| 15–19 | 475 | 10 (2.1) | 4 (0.8) | 480 | 91 (19.0) | 475 | 24 (5.1) | 0 | 6 (1.3) | 129 (27.2) | ||
| 20–29 | 541 | 19 (3.5) | 3 (0.6) | 492 | 25 (5.1) | 486 | 12 (2.5) | 2 (0.4) | 2 (0.4) | 39 (8.0) | ||
| 30–39 | 987 | 56 (5.7) | 1 (0.1) | 991 | 39 (3.9) | 951 | 22 (2.3) | 9 (0.9) | 5 (0.5) | 62 (6.5) | ||
| 40–49 | 977 | 27 (2.8) | 2 (0.2) | 971 | 21 (2.2) | 996 | 18 (1.8) | 7 (0.7) | 5 (0.5) | 42 (4.2) | ||
| 50–59 | 1,396 | 15 (1.1) | 1 (0.1) | 1,283 | 14 (1.1) | 1,179 | 10 (1.8) | 5 (4.2) | 4 (0.3) | 24 (2.0) | ||
|
>60 |
3,472 |
12 (0.3) |
3 (0.1) |
|
3,540 |
8 (0.2) |
|
3,568 |
2 (0.1) |
5 (0.1) |
2 (0.1) |
11 (0.3) |
| Total | 8,856 | 355 (4.0) | 120 (1.4) | 8,763 | 436 (5.0) | 8,652 | 173 (2.0) | 58 (0.7) | 179 (2.1) | 628 (7.3) | ||
*Age during January 2009 (for 2008–09), 2010 (for 2009–10), and 2011 (for 2010–11). †Population recorded in the Resident Registry in January 2009 (for 2008–09), 2010 (for 2009–10), and 2011 (for 2010–11). ‡Influenza A (unspecified). The number of second diagnoses in the season was excluded. §Influenza A(H1N1)pdm09. ¶The sum of influenza A(H1N1)pdm09 cases among residents in Izu-Oshima during the study divided by the population during January 2011.