Volume 16, Number 4—April 2010
Research
Household Transmission of Pandemic (H1N1) 2009, San Antonio, Texas, USA, April–May 2009
Table 2
Household secondary attack rates for ARI, ILI, and laboratory-confirmed pandemic (H1N1) 2009, by age group, Region 8, Texas, April–May 2009*
Illness type by age group, y | No. index case-patients | Household contacts |
Household members not included | Secondary attack rate (A/A + B), % | ||
---|---|---|---|---|---|---|
Secondary case-patients, A | Not ill, B | Total household contacts, A + B | ||||
ARI | ||||||
<5 | 7 | 5 | 23 | 28 | 1 | 18 |
5–18 | 50 | 13 | 83 | 96 | 3 | 14 |
19–49 | 17 | 11 | 96 | 107 | 3 | 10 |
>50 | 3 | 3 | 22 | 25 | 1 | 12 |
All ages |
77 |
32 |
224 |
256 |
8 |
13 |
ILI | ||||||
<5 | 6 | 5 | 23 | 28 | 2 | 18 |
5–18 | 50 | 11 | 86 | 97 | 2 | 11 |
19–49 | 18 | 6 | 102 | 108 | 1 | 6 |
>50 | 3 | 2 | 23 | 25 | 1 | 8 |
All ages |
77 |
24 |
234 |
258 |
6 |
9 |
Laboratory-confirmed pandemic (H1N1) 2009 | ||||||
<5 | 8 | 2 | 26 | 28 | 0 | 7 |
5–18 | 51 | 5 | 92 | 97 | 1 | 5 |
19–49 | 16 | 3 | 108 | 111 | 0 | 3 |
>50 | 2 | 1 | 26 | 27 | 0 | 4 |
All ages | 77 | 11 | 252 | 263 | 1 | 4 |
*ARI, acute respiratory infection; ILI, influenza-like illness (fever measured or subjective and cough or sore throat). Ill household members were not included in the calculation of the secondary attack rate if they had the same symptom onset as the index case or if symptom onset was not known.