Neurological complications associated with influenza in season 2017/18 in Austria- a retrospective single center study

Abstract

Background: Neurological complications associated with influenza (NCI) are rare events in adults with seasonal influenza. Information about the characteristics of neurological complications and the burden of disease has been limited to case reports, mainly during the pandemic 2009. Influenza-associated encephalopathy/encephalitis (IAE) is one of the most severe and frequently reported NCI, mostly caused by influenza A. Isolated case reports exist about NCI caused by influenza B.

Objectives: The aim of this single center retrospective study is the better understanding of the frequency and the characteristics of NCI in adults in season 2017-2018, depending on the influenza subtype A or B.

Study design: We reviewed 874 adult patients with laboratory confirmed influenza admitted to the Christian Doppler University Hospital Salzburg, Austria from December 2017 until March 2018 looking for NCI.

Results: 37 (4 %) of the 874 patients with confirmed influenza had NCI. 4 (11 %) had influenza A and 33 (89 %) had influenza B. IAE was the most frequent complication diagnosed in 24 (65 %) patients, of whom all but one had influenza B and 3 (13 %) had neurological residuals. Moreover 6 (16 %) had isolated epileptic seizures, 2 (5 %) had acute inflammatory demyelinating polyneuropathy (AIDP), and 5 (14 %) were classified as having infection-associated stroke.

Conclusions: We report an incidence of 4 % for NCI and a high frequency of IAE caused by subtype B. Therefore, we recommend considering both influenza A and B as an etiologic factor of encephalopathy and other neurological disease in adults.

Keywords: Influenza B; Influenza neurological complications; Influenza-associated encephalopathy.