Neurologic complications associated with novel influenza A (H1N1) virus infection include seizures, encephalitis, encephalopathy and Reye syndrome. Mania and psychotic episodes are less commonly described, and there have been limited studies on the long-term neuropsychiatric sequelae of H1N1 infection.

Here, we report a case of H1N1 infection with concurrent onset of acute manic and psychotic symptoms. Despite completing a full course of the antiviral medication oseltamivir, the patient's behaviour worsened over the next four weeks and he required readmission for psychiatric treatment. Based on the temporal sequence of events, we considered the possibility that these symptoms were sequelae of Novel influenza A (H1N1) infection. Moreover, the manic symptoms persisted weeks after the acute infection had abated, which gives rise to the consideration of long-lasting direct or indirect neuronal insult by the influenza virus. However, it is also possible that his symptoms may have represented a primary psychiatric disorder precipitated by or coincident with the viral infection.

After treatment with antipsychotic medication and a mood stabiliser, his manic and psychotic symptoms became significantly attenuated. His behaviour improved considerably such that he was able to return to school. Medications were stopped after one month of outpatient follow-up at his behest. Four months after discharge, he was completely free of symptoms and was performing well in school.

Treatment of influenza with antiviral medications has been shown to reduce the rate of complications. However, the effectiveness of antiviral treatment to prevent influenza-associated neuropsychiatric sequelae is unknown.