The difference in mortality between adult patients with laboratory documented influenza A and B, a single centre retrospective observational study.

Background: Seasonal influenza is an annual occurrence that leads to large community outbreaks and increased hospitalization. A number of studies have suggested that influenza A (FLUAV) is associated with increased rates of hospitalization and mortality compared with influenza B (FLUBV). This study compared demographic and clinical variables in patients diagnosed with FLUAV or FLUBV during the 2017-2018 UK Influenza season.

Methods: Patient demographic and clinical information were obtained by accessing medical records of patients testing FLUAV or FLUBV positive using the Cepheid GXP. We used the χ test to compare variables in patients with laboratory-confirmed FLUAV and FLUBV.

Results: One hundred and twenty-seven adult patients had confirmed Influenza, 71 (55.9%) had FLUAV, and 56 (44.1%) FLUBV. There was no significant difference between severity at presentation, admission to HDU/ITU or median length of stay. The overall mortality was 6 (4.5%) and 9 (7.1%) at 7 and 30 days, respectively. There was a statistically significant difference in 7-day mortality between patients with FLUAV and FLUBV, 1 (1.4%) versus 5 (8.9%), respectively, p = .047) although this became nonsignificant at 30 days.

Conclusions: With the exception of mortality, we did not observe significant differences between patients with FLUAV and FLUBV. Seven-day mortality in patients with FLUBV was significantly higher with FLUAV, although this was was not apparent at 30 days.