Tohoku J. Exp. Med., 2016 February, 238(2)

Influenza Virus Shedding in Laninamivir-Treated Children upon Returning to School

HIROKI KONDO,¹ YUGO SHOBUGAWA,¹ AKINOBU HIBINO,¹ REN YAGAMI,¹ CLYDE DAPAT,² MINORU OKAZAKI,³ TAKETO OTSUKA,⁴ KOYATA FUJII,⁵ MOHD ROHAIZAT HASSAN^1,6 and REIKO SAITO¹

¹Division of International Health (Public Health), Graduate School of Medical and Dental Sciences, Niigata University, Niigata, Niigata, Japan
²Department of Virology, Graduate School of Medicine, Tohoku University, Sendai, Miyagi, Japan
³Department of Pediatrics, Sado General Hospital, Niigata, Niigata, Japan
⁴Department of Pediatrics, Graduate School of Medical and Dental Sciences, Niigata University, Niigata, Niigata, Japan
⁵Department of Pediatrics, Niigata Prefectural Shibata Hospital, Niigata, Niigata, Japan
⁶Department of Community Health, Faculty of Medicine, UKM Medical Centre, Kuala Lumpur, Malaysia

The current School Health and Safety Act in Japan states that children with influenza infection should stay home until day 6^th after symptoms onset. This was an amendment of a previous version recommending school return on day 3 after defervescence. Here, we investigated the duration of fever and virus shedding after laninamivir treatment in 7 children infected with influenza A(H3N2) virus and 21 children with influenza B virus in relation to the school return timing recommended by the School Health and Safety Act during the 2011-2012 influenza season. Nasal discharge was collected on the first, second, and third hospital visits and virus titers were assessed by virus culture and real-time PCR. Duration of fever after laninamivir treatment was 1 day longer for influenza B than for influenza A(H3N2). Virus detection rates with 50% tissue culture infectious dose and viral RNA were highest at the first visit and gradually decreased at subsequent visits. Virus positivity rates were detectable at the time of defervescence in less than half of the enrolled patients (14.3-42.9%). Virus shedding rates were similarly low (0.0-19.0%) on day 3 or later from defervescence and on day 6 or later from fever onset (school return dates per the old and current School Health and Safety Act) regardless of the influenza type. In conclusion, despite the higher efficacy of laninamivir against A(H3N2) viruses than B viruses, viral shedding is low after return to school for both types, regardless of the version of the School Health and Safety Act.

keywords —— influenza; laninamivir; period of school absence; school health; virus shedding

© 2016 Tohoku University Medical Press

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Tohoku J. Exp. Med., 2016, 238, 113-121

Correspondence: Hiroki Kondo, Division of International Health (Public Health), Graduate School of Medical and Dental Sciences, Niigata University, 1-757 Asahimachi-dori, Chuo-ku, Niigata, Niigata 951-8510, Japan.

e-mail: kondot@med.niigata-u.ac.jp