Reconstructing the Household Transmission of Influenza in the Suburbs of Tokyo Based on Clinical Cases

Abstract

<jats:title>Abstract</jats:title> <jats:p><jats:bold>Background </jats:bold>Influenza is a public health issue that needs to be addressed strategically and assessment of detailed infectious profiles is important for that. Household transmission data have played a key role for estimating these profiles. From one clinic’s influenza diagnostic and questionnaire-based data, we aimed to estimate the detailed infectious period (incubation, symptomatic and infective, and extended infective after recovery) and secondary attack ratio (SAR) for each household size of influenza by using modified Cauchemez-type model.<jats:bold>Results </jats:bold>The data source was derived from enrolled patients with confirmed influenza who were treated at the Hirotsu Clinic (Kawasaki, Japan) with a neuraminidase inhibitor (NAI) during the 6 Northern Hemisphere influenza seasons between 2010 and 2016. A total of 2,342 outpatients representing 1,807 households were included. For influenza type A, average incubation period and its 95% probability interval was 1.43 (0.03-5.32) days. Estimated average symptomatic and infective period was 1.76 (0.33-4.62) days and point estimated extended infective period after recovery was 0.25 days. Estimated SAR elevated from 20% to 32% as household size increases from 3 to 5. For influenza type B, average incubation period, average symptomatic and infective period, and extended infective period were estimated 1.66 (0.21-4.61) days, 2.62 (0.54-5.75) days and 1.00 days, respectively. SAR was increased 12% to 21% as household size increases from 3 to 5.<jats:bold>Conclusion </jats:bold>All estimated periods of influenza type B were longer than those of influenza type A. On the other hands, SAR of type B was less than that of type A. These results may reflect Japanese demographics and treatment policy. It is useful to understand the infectious profiles of influenza for examining public health measures.</jats:p>