Young influenza victims should be locked inside for the first two days when they recuperate at home to stop them from suffering accidents such as jumping out of windows or falling off balconies, the health ministry has warned.

External doors and windows should be locked and the young sufferers should sleep in a room that has no access to a balcony, the alert states.

It was sent out to all prefectural governments Nov. 27 as fatal accidents caused by the abnormal behavior of sufferers are still being reported regardless of whether they are taking antiviral medication or not.

It is the first time the ministry has made such a specific directive instruction since warning parents and guardians not to leave young flu patients under the age of 20 alone at home for the first two days of treatment in 2007 after several incidents of the abnormal behavior of flu victims were reported.

Abnormal behavior includes the sudden urge to leave a room or rush to a veranda in agitation, talking nonsense and walking around a room weeping. Such behavior was reported regardless of the type of antiviral medication taken and even if nothing was being taken. With reports of fatal incidents continuing, the ministry decided it was time to issue a more specific warning.

Between April 2009 and August 2017 eight people died after falling and for other reasons. They were believed to be demonstrating abnormal behavior after taking anti-flu medication.

During the last flu season, between September 2016 and August 2017, two teenagers who each used Relenza and Inavir died. One plummeted from a high floor in a block of apartments. In both cases, a link between the fatal behavior and the medicine was not established.

Based on statistics by a national research team since 2006, between 40 and 270 cases of dangerous abnormal behavior, including falling from a height or suddenly starting to run, are reported every season. Of those, the percentage of patients who did not take antiviral medication varied from 10 to a few dozen.

“Abnormal behavior could occur regardless of the use of antiviral medicine, and is often seen in the first two days from the onset of fever,” said Nobuhiko Okabe, the director of Health and Safety Research Center of Kawasaki, Kanagawa Prefecture, who is the leader of the national research team. “Keep especially close watch on your children in that period.”