H K Green1, H Zhao1, N L Boddington1, N Andrews2, H Durnall3, A J Elliot4, G Smith4, R Gorton5, M Donati6, J Ellis7, M Zambon7, R Pebody1. 1. Respiratory Diseases Department, Centre for Infectious Disease Surveillance and Control, Public Health England, London NW9 5EQ, UK. 2. Statistics Department, Centre for Infectious Disease Surveillance and Control, Public Health England, London NW9 5EQ, UK. 3. Royal College of General Practitioners Research and Surveillance Centre, Birmingham B17 9DB, UK. 4. Real Time Syndromic Surveillance Team, Public Health England, Birmingham B3 2PW, UK. 5. Field Epidemiology Services North East, Public Health England, Newcastle upon Tyne NE1 4WH, UK. 6. Bristol Public Health Laboratory, Public Health England, Bristol BS2 8EL, UK. 7. Public Health England Respiratory Virus Unit, Virus Reference Department, Reference Microbiology Services, PHE Colindale, London NW9 5EQ, UK.
Abstract
BACKGROUND: Subnational variation of 2009 pandemic influenza activity in England has been reported; however, little work has been published on this topic for seasonal influenza. If variation is present, this knowledge may assist with both identifying the onset of influenza epidemics, informing community antiviral prescription and local health planning. METHODS: An end-of-season analysis of influenza surveillance systems (acute respiratory outbreaks, primary care consultations, virological testing, influenza-confirmed secondary care admissions and excess all-cause mortality) was undertaken at national and subnational levels for 2012/13 when influenza B and A(H3N2) dominated. RESULTS: National community antiviral prescription was recommended in Week 51 following national threshold exceedance. However, this was preceded up to 2 weeks by subnational influenza activity in 2/9 regions in England. Regional variation in circulation of influenza subtypes was observed and severe influenza surveillance data sources were able to monitor the subnational impact. CONCLUSIONS: Evidence of virological activity in two or more regions above a threshold indicated the onset of the 2012/13 season. Subnational thresholds should be determined and evaluated in order to improve timeliness of the national antiviral alert. During the season, outputs should be reported at levels that can inform local public health responses and variation considered when retrospectively evaluating the impact of interventions.
BACKGROUND: Subnational variation of 2009 pandemic influenza activity in England has been reported; however, little work has been published on this topic for seasonal influenza. If variation is present, this knowledge may assist with both identifying the onset of influenza epidemics, informing community antiviral prescription and local health planning. METHODS: An end-of-season analysis of influenza surveillance systems (acute respiratory outbreaks, primary care consultations, virological testing, influenza-confirmed secondary care admissions and excess all-cause mortality) was undertaken at national and subnational levels for 2012/13 when influenza B and A(H3N2) dominated. RESULTS: National community antiviral prescription was recommended in Week 51 following national threshold exceedance. However, this was preceded up to 2 weeks by subnational influenza activity in 2/9 regions in England. Regional variation in circulation of influenza subtypes was observed and severe influenza surveillance data sources were able to monitor the subnational impact. CONCLUSIONS: Evidence of virological activity in two or more regions above a threshold indicated the onset of the 2012/13 season. Subnational thresholds should be determined and evaluated in order to improve timeliness of the national antiviral alert. During the season, outputs should be reported at levels that can inform local public health responses and variation considered when retrospectively evaluating the impact of interventions.
Authors: David Shapiro; Champica K Bodinayake; Ajith Nagahawatte; Vasantha Devasiri; Ruvini Kurukulasooriya; Jeremy Hsiang; Bradley Nicholson; Aruna Dharshan De Silva; Truls Østbye; Megan E Reller; Christopher W Woods; L Gayani Tillekeratne Journal: Am J Trop Med Hyg Date: 2017-07 Impact factor: 2.345