Abnormal behavior during influenza in Japan during the last seven seasons: 2006-2007 to 2012-2013

A few mortalities and cases of severe abnormal behavior have been reported after oseltamivir administration for influenza, thus increasing medical and public concerns regarding the drug's safety. We investigated the association between oseltamivir and abnormal behavior for seven years. All outpatient clinics and hospitals all over the country were requested to report severe abnormal behavior that could have resulted in a fatality if nobody intervened, such as abrupt running outside the home or intention of jumping off a building. The survey was performed prospectively between the 2007-2008 and 2012-2013 seasons, and retrospectively for the 2006-2007 season. As the result of the investigation, eight-hundred fifty-eight cases were reported and among of them 95.7% were positive by the influenza rapid diagnosis test. The epidemic curve of severe abnormal behavior showed a pattern similar to influenza-like illness. The same pattern was observed regardless of age group, gender, or timing of the incidents after waking. Consequently, specific association between the types of medications used or the types of antiviral and abnormal behavior was not observed clearly. The reported abnormal behaviors include fatal cases that would have died if nobody had stopped. This suggested that patients with influenza should be observed with caution for possible abnormal behavior whether taking oseltamivir or other neuraminidase inhibitor anti-influenza drugs.