Weekly epidemiological update

Summary for 18 March 2010 (Week 11)

• Pandemic influenza activity is low and decreasing or stabilised across the UK.
• In week 10 (ending 14 March), the weekly influenza/influenza-like illness (ILI) consultation rate decreased or remained stable in England and Scotland and decreased slightly in Wales and Northern Ireland.
• A decrease in respiratory syncytial virus (RSV) detections has been observed recently, though GP consultation rates for acute bronchitis have increased slightly from week 09 to 10.
• The main influenza virus circulating in the UK continues to be the pandemic (H1N1) 2009 strain, with few influenza H1 (non-pandemic), H3 and B viruses detected. Forty of 5,629 pandemic viruses tested have been confirmed to carry a mutation which confers resistance to the antiviral drug oseltamivir; fifteen are phenotypically resistant to the drug but retain sensitivity to zanamivir.
• The weekly number of pandemic influenza cases reported as admitted to hospital has decreased recently. There have been 457 deaths reported due to pandemic (H1N1) 2009 in the UK.
• The UK pandemic influenza vaccination programme continues for people at high risk for severe disease, health-care workers and healthy children aged between 6 months and 5 years. For further information see the Department of Health website.
• According to WHO on 12 March 2010, the most active areas of pandemic influenza transmission are currently in Southeast Asia, however, lower levels of pandemic virus circulation persist in other parts of Asia and in Eastern and South-eastern Europe. In West Africa, limited data suggest that pandemic influenza virus transmission may be increasing in region. Of note, seasonal influenza B viruses have been increasingly detected in Asia and appear to be spreading westward. Globally, 69.2% of all influenza virus detections were typed as influenza A and 30.8% as influenza B. Of all sub-typed influenza A viruses globally, 92.8% (426/456) were pandemic (H1N1) 2009. Hong Kong SAR China has reported increased influenza B activity in recent weeks accounting for 56.1% of all influenza detections in the reporting week, while in China it accounted for 83.5%.