Hongxin Zhao
Influenza Surveillance Section Respiratory Diseases Department Centre for Infectious Disease Surveillance and Control (CIDSC) Public Health England UK
Title: Epidemiological and virological characteristics of acute respiratory outbreaks during 2014/15 influenza season in the UK
Biography
Biography: Hongxin Zhao
Abstract
The UK has an established respiratory outbreak reporting system used to monitor the activity and impact of influenza. The 2014/15 season has been dominated by the early circulation of A(H3N2). Outbreak reporting from week 40/2014 to 05/2015 has shown 444 acute respiratory outbreaks; 73% (324/444) in elderly care homes, 14% (62/444) in schools, 12% (54/444) in hospitals,. This compares to 122 outbreaks over the whole of 2013/14, 478 in 2012/13 and 230 in 2011/12. Reports of respiratory outbreaks started to increase from week 49/2014, and peaked in week 03/2015. Of 193 outbreaks with testing information, 90% (174/193) were due to influenza A, Fifty (11%) outbreaks reported fatal cases all in care homes. Fatal case numbers ranged from 1 to 17 (CFR 2.2% to 66.7%). Influenza vaccine uptake was available for 87 care homes with a median uptake of 95.0%, (range 11.9% to 100%). Of 42 care home outbreaks with complete information, all were laboratory confirmed to be associated with influenza (26 A(H3), 15 A(not-subtyped), 1 A(H1N1)pdm09 and 1 B). Influenza vaccine effectiveness (VE) could be calculated for 23 outbreaks in care homes with an overall estimated crude VE of -67.8% (range -384.6% to 100%). The higher numbers of reported influenza A confirmed outbreaks in care home settings in 2014/15 in often highly vaccinated populations compared to the previous three seasons was consistent with the pattern of influenza activity observed, where a drifted A(H3N2) variant has emerged and become the dominant strain.