Table 3. Rates of influenza A(H1N1)pdm09-associated influenza-like illness case-patients at three sentinel cities in Argentina, according to age group April–December, 2009.
| Number, Category | Age Group | ||||
| <5 years | 5–44 years | 45–64 years | ≥65 years | All ages | |
| 1. Number of ILI case patients reported to the national influenza surveillance system from sentinel cities when their physicians ordered an influenza laboratory test with date of illness onset information | 17,302 | 68,968 | 11,880 | 3,209 | 101,179 |
| 2. Number (%) of ILI case-patients with respiratory samples of all identified through active surveillance with date of illness onset information | 405/2,268 (18%) | 490/15,514 (3%) | 73/2,624 (3%) | 28/1,117 (3%) | 996/21,523 (5%) |
| 3. Influenza A(H1N1)pdm09 positives among those sampled, n/N (%) | 27/405 (7%) | 157/490 (32%) | 24/73 (33%) | 4/28 (14%) | 212/996 (21%) |
| 4. ILI events among total visits to physicians among residents surveyed , n/(%) | 124/224 (55%) | 286/437 (65%) | 77/113 (68%) | 30/46 (65%) | 517/820 (63%) |
| 5. Estimated number of influenza A(H1N1)pdm09-associated influenza-like illnessesa | 5,996 (95% CI 12,433–1,272) | 339,969 (95% CI 559,282–139,395) | 118,312 (95% CI 42.8–1.7) | 25,761 (95% CI 28,239–24,212) | 283,783 (95% CI 421,897–151,882) |
| 6. Population projections by age group for three cities under active surveillance during 2009 | 222,681 | 1,549,706 | 489,965 | 250,019 | 2,512,370 |
| 7. Rates of 2009 H1N1among health-care seeking ILI case-patients per 100 persons by age group (95% CI)b | 1.6 (95% CI 3.8–0.3) | 15.0 (95% CI 26.6–5.7) | 17.1 (95% CI 42.8–1.7) | 7.1 (95% CI 9.5–5.2) | 7.4 (95% CI 11.8–3.8) |
a
Estimated by multiplying the week-specific number of ILI cases identified (row 1) by the proportion testing positive for 2009 H1N1 (row 3) and its 95% confidence interval by the proportion of ILI cases among ILI physician visits (row 4) while adjusting for the proportion of cases-patients missing data on their epidemiologic week of illness.
b
Corrected for the proportion of case-patients missing date of illness onset (epidemiologic week) information (i.e. 95 of 2,365 among children aged <5 years, 688 of 16,204 among persons aged 5–44, 101 of 2725 among persons aged 45–64 years, and 63 of 1180 among persons aged ≥65 years).