Week 21-26/2017 (22 May – 2 July 2017)

  • Influenza activity has returned to out-of-season levels in all countries. All reporting countries continued to report low influenza intensity.
  • Influenza viruses were detected sporadically both in sentinel and non-sentinel specimens, with influenza B predominating.
  • As of week 26/2017, data from the 19 countries or regions reporting to the EuroMOMO project indicate that over recent months all-cause excess mortality has been at levels expected for the time of year.

Additional information on global influenza activity is available from WHO’s biweekly global updates.

2016/2017 season overview

  • After an earlier start than usual (week 46/2016), influenza activity peaked between weeks 52/2016 and 4/2017. Since week 12/2017, most countries reported decreased influenza activity with the proportion of sentinel detections returning to the epidemic threshold value (10%) in week 17/2017.
  • A(H3N2) viruses predominated during the season.
  • Significant excess all-cause mortality was observed in people aged 15–64 years, and markedly so in people aged 65 years or older, in the majority of the 20 reporting countries or regions. This is commonly seen when the predominant viruses circulating are A(H3N2).
  • Two-thirds of the A(H3N2) viruses genetically characterized belonged to subclade 3C.2a1, but remained antigenically similar to the clade 3C.2a vaccine virus, as described in the WHO recommendations for vaccine composition for the northern hemisphere 2017–18. See also the WHO CC London February 2017 report.
  • Low levels of reduced susceptibility to oseltamivir and zanamivir were observed.

 

Influenza intensity, spread and dominant virus type/subtype