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Letters to the Editor


Effect of the 2009 Influenza A/H1N1 Pandemic on Viral Respiratory Infections in the First Year of Life

Ede, Linda C. MD; Loeffelholz, Michael J. PhD; Alvarez-Fernandez, Pedro MD; Pong, Dan L. MS; Patel, Janak A. MD; McCormick, David P. MD; Chonmaitree, Tasnee MD

Author Information
The Pediatric Infectious Disease Journal: January 2013 - Volume 32 - Issue 1 - p 96
doi: 10.1097/INF.0b013e3182704bd2


We thank Cusinato et al for their comments on our article. As stated in our article,1 the study aimed to define the spectrum of the causative viruses of upper ­respiratory tract infection (URI) and lower respiratory tract infection in infants in the first year of life and to test the hypothesis that the 2009 influenza pandemic caused an increase in incidence of influenza infections in these infants, thus changing the viral epidemiology of URI and lower respiratory tract infection. The data reported, which did not support our original hypothesis, were derived strictly from our ongoing prospective, longitudinal study that began in October 2008. Therefore, data before October 2008 did not exist. We did not intend to report the community impact of the pandemic as in the World Health Organization European region study suggested by Cusinato et al2 and did not include data on visits due to URI or lower respiratory tract infection from entities outside our study. The actual numbers for URI episodes documented, the visits initiated by parents due to URI and the total numbers of active study subjects followed by month between October 2008 and April 2011 (prepandemic, during and postpandemic periods) were shown in Figure 1. We believe this figure clearly illustrated the increased activity of respiratory illnesses during the influenza pandemic in our study population.

As stated in our article, the number of subjects followed in the study was lower at the beginning. Therefore, we also calculated the ratio of documented URI episode(s) per number of subjects actively followed by month and reported it in the results section (range, mean and median). In addition, statistical analysis was performed to show significant increase in the ratios during the influenza pandemic compared with those in the prepandemic and postpandemic periods. As suggested by Cusinato et al, we are providing here a Figure, Supplemental Digital Content 1,, which is a modified Figure 1 showing the ratios between the documented URI episodes and number of the subjects, instead of the actual number of the subjects. The arrows represent the beginning (April 2009) and the end (June 2010) of the influenza A/H1N1 pandemic.

Linda C. Ede, MD

Michael J. Loeffelholz, PhD

Pedro Alvarez-Fernandez, MD

Dan L. Pong, MS

Janak A. Patel, MD

David P. McCormick, MD

Tasnee Chonmaitree, MD

Departments of Pediatrics and Pathology

School of Medicine

University of Texas Medical Branch at Galveston

Galveston, TX


1. Ede LC, Loeffelholz MJ, Alvarez-Fernandez P, et al. Effect of the 2009 influenza A/H1N1 pan–demic on viral respiratory infections in the first year of life. Pediatr Infect Dis J. 2012;31:1107–1112
2. Martirosyan L, Paget WJ, Jorgensen P, et al. The community impact of the 2009 influenza pandemic in the WHO European region: a comparison with historical seasonal data from 28 countries. BMC Infect Dis.. 2012;12:36

Supplemental Digital Content

© 2013 Lippincott Williams & Wilkins, Inc.