Article

Household transmission of pandemic (H1N1) 2009, San Antonio, Texas, USA, April-May 2009

Centers for Disease Control and Prevention, 1600 Clifton Rd NE, Mailstop C12, Atlanta, GA 30333, USA.
Emerging Infectious Diseases (Impact Factor: 7.33). 04/2010; 16(4):631-7. DOI: 10.3201/eid1604.091658
Source: PubMed

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 < or =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 > or =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.

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    • "The overall crude household SAR was 5.7% in our study. Previous studies of household transmission have reported an overall SAR of 5%–24% for seasonal influenza [28], [31]–[33] and 4%–26% for pandemic A(H1N1)2009 [11], [12], [27], [34], [35]. It is difficult to compare this study with previous studies because the study designs are different. "
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