Table 2. Annual pediatric hospitalizations due to influenza A strains in children aged ≤18 y in Hong Kong in comparison with the proportion of positive isolates at the Virology Laboratory of the Department of Health of Hong Kong.
| Year | Overall | H1N1 | H3N2 | H1N1pdm09 | |||
| Hospitalization | Hospitalization (%) | Isolation Proportion (%) | Hospitalization (%) | Isolation Proportion (%) | Hospitalization (%) | Isolation Proportion (%) | |
| 2004 | 2045 | 0 | 0.6% | 2045 (100%) | 99.4% | 0 | - |
| 2005 | 2053¶ | 400 (19.5%) | 8.7% | 1599 (77.9%) | 91.3% | 0 | - |
| 2006 | 1562 | 1499 (96.0%) | 93.7% | 63 (4.0%) | 6.8% | 0 | - |
| 2007 | 2226¶ | 176 (7.9%) | 2.6% | 1994 (89.5%) | 97.4% | 0 | - |
| 2008 | 1940 | 1331 (68.6%) | 51.8% | 609 (31.4%) | 48.2% | 0 | - |
| 2009 | 5832 | 1115 (19.1%) | 8.0% | 1164 (19.9%) | 20.0% | 3553 (61.0%) | 71.7% |
| 3202 * (54.9%) | |||||||
| 2010 | 2112 | 0 | 0 | 1174 (55.6%) | 59.7% | 938 (44.4%) | 40.3% |
| 2011 | 1943 | 0 | 0 | 624 (32.1%) | 25.6% | 1319 (67.9%) | 74.4% |
Influenza strain drifts and shift (in 2009) are denoted in bold.
¶
No subtype available in 2 patients.
* Admissions associated with H1N1pdm09 during the containment period were excluded.