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Volume 17, Number 9—September 2011

Research

Intrahousehold Transmission of Pandemic (H1N1) 2009 Virus, Victoria, Australia

Caroline van GemertComments to Author , Margaret Hellard, Emma S. McBryde, James Fielding, Tim Spelman, Nasra Higgins, Rosemary Lester, Hassan Vally1, and Isabel Bergeri
Author affiliations: Author affiliations: Burnet Institute, Melbourne, Victoria, Australia (C. van Gemert, M. Hellard, E.S. McBryde, T. Spelman, I. Bergeri); Australian National University, Canberra, Australian Capital Territory, Australia (C. van Gemert, J. Fielding, H. Vally); Monash University, Melbourne (M. Hellard); Victorian Department of Health, Melbourne (E.S. McBryde, J. Fielding, N. Higgins, R. Lester); Royal Melbourne Hospital, Melbourne (E.S. McBryde); University of Melbourne, Melbourne (E.S. McBryde); Victorian Infectious Diseases Reference Laboratory, Melbourne (J. Fielding)

Main Article

Table 4

Secondary attack rates for susceptible household contacts of index case-patients with pandemic (H1N1) 2009, Victoria, Australia, May 18–June 3, 2009*

Variable Total no. household contacts No. with influenza-like illness Secondary attack rate, % (95% CI)
Individual-level associations
Sex
M 58 5 8.62 (1.08–14.4)
F 64 13 20.3 (11.3–32.2)
Age, y
0–4 11 1 9.09 (0.230–41.3)
5–19 35 6 17.1 (6.50–33.6)
20–49 66 10 15.2 (7.51–26.1)
>50 10 1 10.0 (0.25–44.5)
Relationship to index case-patient
Parent/child/partner 65 10 15.4 (7.63–26.5)
Sibling 44 8 18.2 (8.19–32.7)
Other family member
13
0
0 (0–24.7)
Prevention and control measures reported
Antiviral prophylaxis 57 1 1.8 (0.04–9.39)
Quarantined >1 d with index case-patient
73
15
20.5 (12.0–31.6)
Household-level associations
No. persons
2–3 7 2 28.6 (3.67–71.0)
4–5 75 10 13.3 (6.58–23.2)
>6 40 6 15.0 (5.71–29.8)
No. children
1 31 6 19.4 (7.45–37.5)
2 47 7 14.9 (6.20–28.3)
>3 44 5 11.4 (3.79–24.6)
Cultural and linguistic diversity
Only English spoken at home 53 5 9.4 (3.13–20.7)
English and/or other language(s) spoken at home 69 13 18.8 (10.4–30.1)

*CI, confidence interval.

Main Article

1Current affiliation: La Trobe University, Melbourne, Victoria, Australia.

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