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Volume 18, Number 9—September 2012


Demographic Shift of Influenza A(H1N1)pdm09 during and after Pandemic, Rural India

Shobha BroorComments to Author , Wayne Sullender, Karen Fowler, Vivek Gupta, Marc-Alain Widdowson, Anand Krishnan, and Renu B. Lal
Author affiliations: All India Institute of Medical Sciences, New Delhi, India (S. Broor, A. Kirshnan); University of Alabama, Birmingham, Alabama, USA (W. Sullender, K. Fowler); The Inclen Trust International, New Delhi (V. Gupta); and Centers for Disease Control and Prevention, Atlanta, Georgia, USA (M.-A. Widdowson, R.B. Lal)

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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.

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