13 April 2012- Update number 157
Table of content
•In most areas of the northern hemisphere temperate regions, influenza activity appears to have peaked and is declining. In North America, influenza indicators have remained elevated in some areas of the United States of America, but declined in the last couple of weeks. Although, activity remains elevated across several regions in Canada, declining trends have started to be observed. Similarly, in Europe and northern Asia, nearly every country has now passed its peak of transmission and has reported declining activity.
•The most commonly detected virus type or subtype throughout Europe and North America (except Mexico) has been influenza A(H3N2), although the proportion of influenza B detection has been increasing toward the end of the season in North America. In Mexico influenza A(H1N1)pdm09 has been the most common influenza virus circulating; China and the surrounding countries of northern Asia are still reporting a predominance of influenza type B virus.
•Increasing genetic and antigenic diversity has been noted in H3N2 viruses in the later part of the influenza season.
• No significant change in antiviral resistance has been reported so far this season.
Source of data
The Global Influenza Programme monitors influenza activity worldwide and publishes an update every two weeks.
The updates are based on available epidemiological and virological data sources, including FluNet (reported by the Global Influenza Surveillance and Response System) and influenza reports from WHO Regional Offices and Member States. Completeness can vary among updates due to availability and quality of data available at the time when the update is developed.