Monday, December 26, 2016

ECDC Seasonal Flu Risk Assessment


While we are starting to see some reports of heavy flu activity in Russia and Eastern Europe, so far North America and Western Europe have only been mildly affected this winter.  That could change, however, as influenza often doesn't peak until February or March. 

This fall H3N2 has been the subtype most commonly reported, and this strain is often associated with more severe flu seasons, particularly for the elderly. 

Today the ECDC has released an updated risk assessment for seasonal flu, along with a brief characterization of a new clade of H3N2 which has emerged (see below).
Virus characteristics
By week 49/2016, circulating A(H3N2) viruses belonged mainly to two genetic groups: the pre-existing clade A/Hong Kong/4801/2014 3C.2a (vaccine virus) and a new emerging clade A/Bolzano/7/2016 3C.2a1 (Table 1), both matching well with the reference viruses (data not shown), with this new clade being found to be antigenically similar to the vaccine strain.

Follow the link to read the RRA in full. I've reproduced the summary below:

Risk assessment of seasonal influenza, EU/EEA, 2016/2017, 24 December 2016

Main conclusions and options for response

This season, influenza viruses, mainly A(H3N2), began circulating early in the EU/EEA. It is too early to anticipate the intensity in primary care and severity in secondary care, but if A(H3N2) continues to predominate, there is a risk that people over 65 years of age will be the most severely affected, possibly putting some healthcare systems under pressure. Influenza A(H1N1)pdm09 may dominate in a few countries where A(H3N2) was dominant last season (Slovenia and Italy).

Although just over half of the A(H3N2) viruses characterised at this early stage of the season belong to a new genetic clade, they all are antigenically less than four-fold different from the vaccine strain in the haemagglutination inhibition test. 

Preliminary vaccine effectiveness (VE) estimates from Scandinavia suggest levels of effectiveness towards the upper range of those seen during the period 2011—2015. 

Given the early epidemiological and VE data, vaccination of the elderly and other high-risk individuals remains a priority, in line with the national recommendations of the EU/EEA Member States, to prevent more severe cases. Given the partial effectiveness of influenza vaccines, rapid use of neuraminidase inhibitors for laboratory-confirmed or probable cases of influenza should be considered for vaccinated and non-vaccinated at-risk patients.
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