Household Transmission of Pandemic (H1N1) 2009, San Antonio, Texas, USA, April–May 2009

EID Journal Home > Volume 16, Number 4–April 2010

Volume 16, Number 4–April 2010
Research
Household Transmission of Pandemic (H1N1) 2009, San Antonio, Texas, USA, April–May 2009
Oliver W. Morgan, Sharyn Parks, Trudi Shim, Patricia A. Blevins, Pauline M. Lucas, Roger Sanchez, Nancy Walea, Fleetwood Loustalot, Mark R. Duffy, Matthew J. Shim, Sandra Guerra, Fernando Guerra, Gwen Mills, Jennifer Verani, Bryan Alsip, Stephen Lindstrom, Bo Shu, Shannon Emery, Adam L. Cohen, Manoj Menon, Alicia M. Fry, Fatimah Dawood, Vincent P. Fonseca, and Sonja J. Olsen

Author affiliations: Centers for Disease Control and Prevention, Atlanta, Georgia, USA (O.W. Morgan, S. Parks, F. Loustalot, J. Verani, S. Lindstrom, B. Shu, S. Emery, A.L. Cohen, M. Menon, A.M. Fry, F. Dawood, S.J. Olsen); Department of State Health Services, Austin, Texas, USA (S. Parks, T. Shim, N. Walea, S. Guerra, V.P. Fonseca); United States Air Force School of Aerospace Medicine, Brooks City-Base, Texas, USA (P.M. Lucas, M.R. Duffy, M.J. Shim); San Antonio Metropolitan Health District, San Antonio, Texas, USA (P.A. Blevins, R. Sanchez, F. Guerra, B. Alsip); and Comal County Health Department, New Braunfels, Texas, USA (G. Mills)

Suggested citation for this article

Abstract
To assess household transmission of pandemic (H1N1) 2009 in San Antonio, Texas, USA, during April 15–May 8, 2009, we investigated 77 households. The index case-patient was defined as the household member with the earliest onset date of symptoms of acute respiratory infection (ARI), influenza-like illness (ILI), or laboratory-confirmed pandemic (H1N1) 2009. Median interval between illness onset in index and secondary case-patients was 4 days (range 1–9 days); the index case-patient was likely to be <18 years of age (p = 0.034). The secondary attack rate was 4% for pandemic (H1N1) 2009, 9% for ILI, and 13% for ARI. The secondary attack rate was highest for children <5 years of age (8%–19%) and lowest for adults >50 years of age (4%–12%). Early in the outbreak, household transmission primarily occurred from children to other household members and was lower than the transmission rate for seasonal influenza.

On April 15 and 17, 2009, the first 2 cases of pandemic (H1N1) 2009 in the United States were identified among children in California; within 10 weeks, the strain was identified in 99 countries or territories (1). Texas was the second US state to confirm human transmission of pandemic (H1N1) 2009. On April 24, 2009, the Texas Department of State Health Services reported 2 patients with laboratory-confirmed pandemic (H1N1) 2009 infection in Guadalupe County. The strain was similar to that isolated previously from patients in Mexico and California (2). On June 11, 2009, the World Health Organization raised the pandemic alert to phase 6, indicating that a global pandemic was under way (3).

Characterizing transmission dynamics in various settings, such as households, schools, and the community, is critical to the development of appropriate guidance and public health interventions. Household contacts of persons with seasonal influenza are at increased risk for infection (4–7), but the household transmission characteristics of pandemic (H1N1) 2009 have yet to be fully characterized. This study reports household secondary attack rates and serial time intervals between illness onset in the index case-patient to illness onset in a household contact. We investigated persons with laboratory-confirmed pandemic (H1N1) 2009 and their household contacts in 1 health service region of Texas.

Suggested Citation for this Article
Morgan OW, Parks S, Shim T, Blevins PA, Lucas PM, Sanchez R, et al. Household transmission of pandemic (H1N1) 2009, San Antonio, Texas, USA, April–May 2009. Emerg Infect Dis [serial on the Internet]. 2010 Apr [date cited]. http://www.cdc.gov/EID/content/16/4/631.htm

DOI: 10.3201/eid1604.091658

open here to see the full-text:
http://www.cdc.gov/eid/content/16/4/631.htm