Unusually high impact of influenza B during the early 2012–2013 influenza season in Wales – epidemiology and clinical analysis of the first 100 cases

Background Influenza B is often regarded as the milder form of the disease. The early 2012–2013 season in Wales saw the highest rate of influenza B‐associated primary care consultations since 1994–1995 and considerable hospitalisations. Objectives This report summarises features of the first 100 confirmed cases during 2012–2013 in Wales. Methods Case information was sourced from routine laboratory testing and virological surveillance. Results and conclusions Influenza B (Yamagata lineage) viruses dominated, mainly affecting younger adults, admission to critical care was unexpectedly common. Low vaccine uptake amongst at‐risk patients may have contributed to the burden of influenza in secondary care in Wales.