Table 1. Demographic data for persons under surveillance and incidence of febrile ARI and influenza A(H1N1)pdm09 during pandemic and postpandemic periods, Ballabgarh, India*.
| Demographics and test results | Pandemic period, November 2009–January 2010 | Postpandemic period, August–October 2010 |
|---|---|---|
| Mean no. persons under surveillance (person-years) | 7,340 (1,835) | 16,396 (4,134) |
| No. febrile ARI episodes (incidence rate/1,000 person-years) | 1,515 (826) | 4,933 (1,203) |
| No. (%) persons tested for influenza | 1,094 (72) | 3,907 (79) |
| No. (%) positive for influenza | 265 (24) | 902 (23)† |
| No. (%) positive for influenza A(H1N1)pdm09 | 231 (21) | 506 (13) |
| No. (%) positive for influenza B | 34 (3) | 377 (10) |
| Influenza incidence rate/1,000 person-years | 205‡ | 278 |
| Median age, y (interquartile range) | ||
| All persons with influenza | 9 (4–17) | 15 (6–30)§ |
| Persons with influenza A(H1N1)pdm09 | 9 (5–18) | 18 (7–32)§ |
| Persons with Influenza B | 7.5 (4–16) | 13 (5–27) |
*ARI, acute respiratory infection. †Total no. positive during postpandemic period included 18 persons with influenza A (H3N2) infection and 1 person co-infected with influenza B and A(H1N1)pdm09. ‡The rate of influenza positivity of sampled febrile ARI case-patients was adjusted to unsampled case-patients assuming similar characteristics for the 2 groups. §Wilcoxon rank-sum test, p<0.001.