Primary care data

Influenza activity

Influenza activity in week 6/2017 was at variable levels across the region but slightly lower compared to the previous week: of the 43 countries reporting on influenza activity, 24 countries reported high or medium intensity (Fig. 1) and 22 reported widespread influenza activity (Fig.2).

The percentage of influenza virus detections among sentinel specimens was 42%, the lowest it has been since week 52/2016 (51-52%) and slightly decreased from 45% in week 5/2017. 42 countries reported on influenza virus dominance: 23 reported subtype A(H3), four type A and 15 no dominant type/subtype.



Viruses detected in sentinel-source specimens (ILI and ARI)

For week 6/2017, 1 090 of 2 601 (42%) sentinel specimens tested positive for influenza viruses (Table 1). Of these, 92% were type A and 8% were type B. The great majority (99%) of subtyped influenza A viruses were A(H3N2). The lineage of 45 influenza B viruses was determined of which 32 (71%) fell in B/Yamagata and 13 (29%) in B/Victoria lineages.  Of 30 countries across the region that each tested at least 10 sentinel specimens, 19 reported proportions of influenza virus detections above 30% (median 52, range 36% to 68%).

Since week 40/2016, similar cumulative distributions of influenza types and type A subtypes have been observed: of all typed viruses, 95% were type A, with 99% of those subtyped being A(H3N2).(Figure 3, Table 1). Of the 344 influenza B viruses which have been ascribed a lineage since week 40/2017, 182 (53%) were of the B/Victoria lineage and 162 (47%) were of the B/Yamagata lineage. The slight predominance of the B/Victoria lineage detections is due to reports from Kyrgyzstan where 137 (75%) of the 182 B/Victoria viruses were detected.