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Br J Gen Pract. 2004 Sep;54(506):684-9.

Risk factors of influenza transmission in households.

Author information

  • 1Epidemiology and Information Sciences, Université Pierre et Marie Curie, Paris. viboudc@mail.nih.gov

Abstract

BACKGROUND:

Influenza transmission in households is a subject of renewed interest, as the vaccination of children is currently under debate and antiviral treatments have been approved for prophylactic use.

AIMS:

To quantify the risk factors of influenza transmission in households.

DESIGN OF STUDY:

A prospective study conducted during the 1999 to 2000 winter season in France.

SETTING:

Nine hundred and forty-six households where a member, the index patient, had visited their general practitioner (GP) because of an influenza-like illness were enrolled in the study. Five hundred and ten of the index patients tested positive for influenza A (subtype H3N2). A standardised daily questionnaire allowed for identification of secondary cases of influenza among their household contacts, who were followed-up for 15 days. Of the 395 (77%) households that completed the questionnaire, we selected 279 where no additional cases had occurred on the day of the index patient's visit to the GP.

METHODS:

Secondary cases of influenza were those household contacts who had developed clinical influenza within 5 days of the disease onset in the index patient. Hazard ratios for individual clinical and demographic characteristics of the contact and their index patient were derived from a Cox regression model.

RESULTS:

Overall in the 279 households, 131 (24.1%) secondary cases occurred among the 543 household contacts. There was an increased risk of influenza transmission in preschool contacts (hazard ratio [HR] = 1.85, 95% confidence interval [CI] = 1.09 to 3.26) as compared with school-age and adult contacts. There was also an increased risk in contacts exposed to preschool index patients (HR = 1.93, 95% CI = 1.09 to 3.42) and school-age index patients (HR = 1.68, 95% CI = 1.07 to 2.65), compared with those exposed to adult index cases. No other factor was associated with transmission of the disease.

CONCLUSION:

Our results support the major role of children in the dissemination of influenza in households. Vaccination of children or prophylaxis with neuraminidase inhibitors would prevent, respectively, 32-38% and 21-41% of secondary cases caused by exposure to a sick child in the household.

Comment in

PMID:
15353055
[PubMed - indexed for MEDLINE]
PMCID:
PMC1326070
Free PMC Article
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