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Volume 17, Number 9—September 2011

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 5

Unadjusted associations with secondary transmission for pandemic (H1N1) 2009, Victoria, Australia, May 18–June 3, 2009*

Variable OR (95% CI) p value
Individual level
M 1.00
F 2.70 (1.060–6.860) 0.037
Age, y
0–4 1.00
5–19 2.06 (0.179–23.90) 0.560
20–49 1.79 (0.228–14.00) 0.581
>50 1.11 (0.529–23.30) 0.946
Relationship to index case-patient
Parent/child/partner 1.00
Sibling 1.22 (0.562–2.660) 0.613
Other family member

Reported prevention and control measures
Antiviral prophylaxis‡ 0.05 (0.006–0.429) 0.006
Quarantined for >1 d
with index case-patient§
1.22 (1.03–1.44)
Household level
No. persons
2–3 1.00
4–5 0.385 (0.035–4.280) 0.437
>6 0.441 (0.024–8.070) 0.581
No. children
1 1.00
2 0.729 (0.163–3.260) 0.679
>3 0.534 (0.05–5.74) 0.605
Cultural and linguistic diversity
Only English spoken at
home 1.00
English and/or other
language(s) spoken at
home 2.23 (0.448–11.100) 0.328

*Backwards stepwise selection procedures were used to develop the final adjusted model whereby predictors (p>0.05) were removed sequentially until only significant predictors (p<0.05) remained. Gender was not significant in the adjusted model (p = 0.83) and was thus removed. Goodness of fit for both models was assessed by using the Hosmer and Lemeshow test to 0.05 significance. Goodness of fit for the final model was 0.2. OR, odds ratio; CI, confidence interval.
†No secondary cases occurred in this group, and this level is not included in the unadjusted model.
‡Adjusted OR 0.042 (95% CI 0.004–0.434); p = 0.008.
§Logistic regression using number of days quarantined with index case-patient as continuous exposure. Adjusted OR 1.25 (95% CI 1.06–1.47); p = 0.008.

Main Article

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

Page created: September 06, 2011
Page updated: September 06, 2011
Page reviewed: September 06, 2011
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