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Volume 17, Number 10—October 2011

Research

Pandemic (H1N1) 2009 among Quarantined Close Contacts, Beijing, People’s Republic of China

Xinghuo Pang1, Peng Yang1, Shuang Li, Li Zhang, Lili Tian, Yang Li, Bo Liu, Yi Zhang, Baiwei Liu, Ruogang Huang, Xinyu Li, and Quanyi WangComments to Author 

Author affiliations: Beijing Center for Disease Prevention and Control, Beijing, People’s Republic of China; Capital Medical University School of Public Health and Family Medicine, Beijing

Main Article

Table 4

Factors significantly associated with infection of pandemic (H1N1) 2009 virus in close contacts in multivariate analysis*

Factor All close contacts†
Flight passenger contacts‡
Nonflight passenger contacts§
OR (95% CI) p value OR (95% CI) p value OR (95% CI) p value
Age of close contacts, y
>50 Reference Reference Reference
20–50 3.42 (1.56–7.48) 0.002 3.13 (0.40–24.76) 0.280 2.89 (1.23–6.80) 0.015
0–19
7.76 (3.52–17.09)
<0.001

13.33 (1.77–100.22)
0.012

4.97 (2.06–12.00)
<0.001
Relationship to index case-patient
Nonhousehold member Reference NA Reference
Household member
3.83 (2.65–5.53)
<0.001

NA
NA

2.37 (1.58–3.55)
<0.001
Type of exposure to index case-patient
During asymptomatic phase¶ Reference Reference Reference
During symptomatic phase
1.86 (1.23–2.80)
0.003

NA
NA

1.79 (1.09–2.93)
0.021
Exposure duration of close contacts, h
<12 Reference Reference Reference
>12 1.83 (1.25–2.67) 0.002 3.41 (1.49–7.78) 0.004 NA NA

*Variables with p<0.1 in Table 2 were included in multivariate unconditional logistic regression analysis. Hosmer-Lemeshow goodness-of-fit test was used to assess the model fit for logistic regression. OR, odd ratio; CI, confidence interval; NA, not available, indicating not included in the final model.
†One dependent variable (infection with pandemic [H1N1] 2009 virus) and 5 independent variables (age of index case-patient, type of exposure to index case-patients, age of close contacts, relationships to index case-patients, and exposure duration of close contacts) were included in multivariate analysis. One independent variable (age of index case-patient) was removed in the stepwise regression equation. The goodness-of-fit test suggested that the logistic regression model fitted well (p = 0.631).
‡One dependent variable (infection with pandemic [H1N1] 2009 virus) and 4 independent variables (age of index case-patient, type of exposure to index case-patient, age of close contacts, and exposure duration of close contacts) were included in multivariate analysis. Two independent variables (age of index case-patient and type of exposure to index case-patient) were removed in the stepwise regression equation. The goodness-of-fit test suggested that the logistic regression model fitted well (p = 0.982).
§One dependent variable (infection with pandemic [H1N1] 2009 virus) and 5 independent variables (age of index case-patient, type of exposure to index case-patient, age of close contacts, relationships to index case-patient, and exposure duration of close contacts) were included in multivariate analysis. Two independent variables (age of index case-patient and exposure duration of close contacts) were removed in the stepwise regression equation. The goodness-of-fit test suggested the logistic regression model fitted well (p = 0.751).
¶Exposed to symptomatic index case-patients before their illness onset or exposed to index case-patients who had subclinical infections.

*Variables with p<0.1 in Table 2 were included in multivariate unconditional logistic regression analysis. Hosmer-Lemeshow goodness-of-fit test was used to assess the model fit for logistic regression. OR, odd ratio; CI, confidence interval; NA, not available, indicating not included in the final model.
†One dependent variable (infection with pandemic [H1N1] 2009 virus) and 5 independent variables (age of index case-patient, type of exposure to index case-patients, age of close contacts, relationships to index case-patients, and exposure duration of close contacts) were included in multivariate analysis. One independent variable (age of index case-patient) was removed in the stepwise regression equation. The goodness-of-fit test suggested that the logistic regression model fitted well (p = 0.631).
‡One dependent variable (infection with pandemic [H1N1] 2009 virus) and 4 independent variables (age of index case-patient, type of exposure to index case-patient, age of close contacts, and exposure duration of close contacts) were included in multivariate analysis. Two independent variables (age of index case-patient and type of exposure to index case-patient) were removed in the stepwise regression equation. The goodness-of-fit test suggested that the logistic regression model fitted well (p = 0.982).
§One dependent variable (infection with pandemic [H1N1] 2009 virus) and 5 independent variables (age of index case-patient, type of exposure to index case-patient, age of close contacts, relationships to index case-patient, and exposure duration of close contacts) were included in multivariate analysis. Two independent variables (age of index case-patient and exposure duration of close contacts) were removed in the stepwise regression equation. The goodness-of-fit test suggested the logistic regression model fitted well (p = 0.751).
¶Exposed to symptomatic index case-patients before their illness onset or exposed to index case-patients who had subclinical infections.

*Variables with p<0.1 in Table 2 were included in multivariate unconditional logistic regression analysis. Hosmer-Lemeshow goodness-of-fit test was used to assess the model fit for logistic regression. OR, odd ratio; CI, confidence interval; NA, not available, indicating not included in the final model.
†One dependent variable (infection with pandemic [H1N1] 2009 virus) and 5 independent variables (age of index case-patient, type of exposure to index case-patients, age of close contacts, relationships to index case-patients, and exposure duration of close contacts) were included in multivariate analysis. One independent variable (age of index case-patient) was removed in the stepwise regression equation. The goodness-of-fit test suggested that the logistic regression model fitted well (p = 0.631).
‡One dependent variable (infection with pandemic [H1N1] 2009 virus) and 4 independent variables (age of index case-patient, type of exposure to index case-patient, age of close contacts, and exposure duration of close contacts) were included in multivariate analysis. Two independent variables (age of index case-patient and type of exposure to index case-patient) were removed in the stepwise regression equation. The goodness-of-fit test suggested that the logistic regression model fitted well (p = 0.982).
§One dependent variable (infection with pandemic [H1N1] 2009 virus) and 5 independent variables (age of index case-patient, type of exposure to index case-patient, age of close contacts, relationships to index case-patient, and exposure duration of close contacts) were included in multivariate analysis. Two independent variables (age of index case-patient and exposure duration of close contacts) were removed in the stepwise regression equation. The goodness-of-fit test suggested the logistic regression model fitted well (p = 0.751).
¶Exposed to symptomatic index case-patients before their illness onset or exposed to index case-patients who had subclinical infections.

Main Article

1These authors contributed equally to this article.

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