WHO : Influenza update 153

From WHO, excerpt :

" Summary

• Influenza activity in the temperate regions of the northern hemisphere remains low overall. It has continued to increase in the United States and Canada, though overall activity is low. Some countries of western Europe, North Africa, and northern China appear to have reached peak transmission but activity continues to increase in eastern Europe. The levels of both mild and severe disease have been relatively low compared to previous years in most areas reporting.

•Countries in the tropical zone reported low levels of influenza activity with the exception of a few countries in the Americas and parts of southern Asia.

• The most commonly detected virus type or subtype throughout the northern hemisphere temperate zone has been influenza A(H3N2) with the exception of Mexico, where influenza A(H1N1)pdm09 is the predominant subtype circulating, and China and the surrounding countries which are reporting a predominance of influenza type B.

• Notable differences have been reported in the distribution of viruses in severe cases and between age groups. In Canada, influenza A(H1N1)pdm09 accounted for 27% of all influenza A viruses that have been subtyped in <5 year olds but only 5% of subtyped influenza A viruses in cases over the age of 65 years. In Europe, influenza A(H1N1)pdm09 was disproportionately found in cases admitted to hospital for severe acute respiratory infection compared to outpatient cases of influenza-like illness (13-20% vs. ~1.5% respectively).

• Nearly all influenza A viruses detected were antigenically related to the viruses contained in the current northern hemisphere trivalent vaccine.

• Oseltamivir resistance continues to be observed at very low levels and has not increased notably over levels reported in previous seasons."