Abstract
BackgroundHousehold transmission of influenza can affect the daily lives of patients and their families and be a trigger for community transmission, thus it is necessary to take precautions to prevent household transmission. We aimed to determine the risks of household transmission of pandemic (H1N1) 2009 influenza virus from an index patient who visited a primary clinic and was treated with antiviral drugs.MethodsWe followed up all the patients who were diagnosed with influenza A by rapid diagnostic test with a questionnaire or interview from July 2009 to April 2010. Secondary cases were defined as patients visiting the clinic or other clinics and being positive for influenza A by rapid diagnostic test within 7 days of onset of an index patient. Logistic regression analysis was used to explore the association between household transmission and the studied variables.ResultsWe recruited 591 index patients and 1629 household contacts. The crude secondary attack rate was 7.3% [95% confidence interval (CI): 6.1–8.7]. Age of index patients (0–6 years old: odds ratio 2.56; 95% CI: 1.31–4.01; 7–12 years old: 2.44, 1.31–3.72; 30–39 years old 3.88; 2.09–5.21; 40 years old or more 2.76; 1.17–4.53) and number of household members with five or more (3.09, 2.11–4.07), medication started ≥48 hours from the onset of fever (2.38, 1.17–3.87) were significantly associated with household transmission.ConclusionsHousehold transmission was associated with index patients aged ≤12 years old and adults ≥30 years with children, with more than five persons in the household, and medication initiated ≥48 hours from the onset of fever among the population, in which, antiviral treatment was given to all patients. We need to warn patients at high risk of household transmission to take additional precautions.
Highlights
The household of an influenza patient could be at high risk of infection [1,2,3]
119 secondary cases occurred among 1629 household contacts, giving a secondary attack rate (SAR) of 7.3%
The present prospective cohort study elucidated the risk factors that were associated with household transmission among the patients infected with influenza A, with antiviral drug treatment during the first wave of pandemic influenza virus (H1N1) 2009 at a primary clinic in Japan
Summary
The household of an influenza patient could be at high risk of infection [1,2,3]. The secondary attack rate (SAR) of pandemic (H1N1) 2009 in 2009 was 10–45% [1,2,3,4,5,6,7]. Household transmission could result in the burden of taking care of patients at home for several days and affect their daily lives, and an additional financial burden because parents cannot go to work [8,9]. A variety of risk factors have been identified, such as age of the index patient and number of household members [2,3,4,6,10,11]. Household transmission of influenza can affect the daily lives of patients and their families and be a trigger for community transmission, it is necessary to take precautions to prevent household transmission. We aimed to determine the risks of household transmission of pandemic (H1N1) 2009 influenza virus from an index patient who visited a primary clinic and was treated with antiviral drugs
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