Hypomanic switching during influenza infection without intracranial infection in an adolescent patient with bipolar disorder.

Manic switching, which is mood changing from depression to mania, induced by intracranial viral infections have been previously reported. However, manic switching induced by influenza infection without intracranial viral infection in a patient with bipolar disorder (BD), has not been previously reported. We report a patient with adolescent BD who showed a first episode of hypomanic switching during influenza B infection without intracranial viral infection. In addition to neurological monitoring, careful psychiatric interventions for hypomanic state is very important to prevent inappropriate treatment of BD and reduce the risk of suicide attempts in cases presenting with hypomanic symptoms during influenza infection.