| Caritas(n = 256) | Sage(n = 204) | Shui On(n = 221) | Cambridge(n = 90) | Total(n = 771) | |
| Total number with ILI | 83 (32.4) | 62 (30.4) | 86 (38.9) | 28 (31.1) | 259 (33.6) |
| Date of onset | |||||
| April | 1 (0.4) | 8 (3.9) | 11 (5.0) | 6 (6.7) | 26 (3.4) |
| May | 5 (2.0) | 5 (2.5) | 11 (5.0) | 1 (1.1) | 22 (2.9) |
| June | 7 (2.7) | 10 (4.9) | 4 (1.8) | 5 (5.6) | 26 (3.4) |
| July | 10 (3.9) | 7 (3.4) | 7 (3.2) | 0 | 24 (3.1) |
| August | 7 (2.7) | 1 (0.5) | 7 (3.2) | 2 (2.2) | 17 (2.2) |
| September | 8 (3.1) | 5 (2.5) | 4 (1.8) | 1 (1.1) | 18 (2.3) |
| October | 11 (4.3) | 3 (1.5) | 7 (3.2) | 2 (2.2) | 23 (3.0) |
| November | 9 (3.5) | 4 (2.0) | 3 (1.4) | 1 (1.1) | 17 (2.2) |
| December | 3 (1.2) | 2 (1.0) | 4 (1.8) | 2 (2.2) | 11 (1.4) |
| Jan | 2 (0.8) | 4 (2.0) | 7 (3.2) | 2 (2.2) | 15 (1.9) |
| Feb | 5 (2.0) | 5 (2.5) | 3 (1.4) | 2 (2.2) | 15 (1.9) |
| Mar | 15 (5.8) | 8 (4.0) | 18 (8.2) | 4 (4.4) | 45 (5.9) |
| April–June | 13 (5.1) | 23 (11.3) | 26 (11.8) | 12 (13.3)* | 74 (9.6) |
| July–Sept | 25 (9.8) | 13 (6.4) | 18 (8.1) | 3 (3.3) | 59 (7.7) |
| Oct–Dec | 23 (9.0) | 9 (4.4) | 14 (6.3) | 5 (5.6) | 51 (6.6) |
| Jan–March | 22 (8.6) | 17 (8.4) | 28 (12.7) | 8 (8.9) | 75 (9.7) |
Data are shown as n (%).
*Difference in numbers of ILI between homes according to four seasons, p = 0.026 (χ2 test).