Weekly influenza update, week 1, January 2018
ECDC and WHO/Europe publish weekly influenza surveillance data in the report Flu News Europe.
- Influenza activity was increasing in countries in northern, southern and western Europe.
- Both influenza type A and B viruses were co-circulating and different patterns of circulation were observed across countries in the Region.
- Of the individuals sampled, on presenting with ILI or ARI to sentinel primary healthcare sites, 42% tested positive for influenza viruses, similar to the 44% in the previous week.
- EuroMOMO data showed excess mortality in the elderly (>65 years of age) for the United-Kingdom (Scotland), Spain and Portugal.
2017/18 season overview
From sentinel sources, a higher proportion of type B viruses compared to type A viruses has been detected. Of the type A detections, A(H1N1)pdm09 viruses have outnumbered A(H3N2) viruses.
For type B viruses from both sentinel and non-sentinel sources, B/Yamagata lineage viruses have greatly outnumbered those of the B/Victoria lineage.
While low in number, 64% of the genetically characterized A(H3N2) viruses belonged to clade 3C.2a, the vaccine virus clade as described in the WHO recommendations for vaccine composition for the northern hemisphere 2017–18, and 36% to clade 3C.2a1, with viruses in both clades being antigenically similar.
Based on data submitted to the EuroMOMO project there has, over the past weeks, been increased mortality among the elderly, notably in the southwest and the north of the British Isles.
An early risk assessment based on data from EU/EEA countries was published by ECDC on 20 December 2017. First detections indicated circulation of A(H3N2) and B/Yamagata viruses in the highest proportions. As the A(H3N2) subtype dominated last season, a high proportion of the population should be protected.
- The US CDC published a Health Alert Network (HAN) notice, regarding increased A(H3N2) activity that affects mostly people aged over 65 and younger children, leading to more hospitalizations and deaths. Based on the moderate vaccine effectiveness, detailed information on recommended antiviral treatment is provided. See full report here.
- Additional information on global influenza activity is available from WHO’s biweekly global updates.