Weekly epidemiological update

Due to low influenza activity the National Influenza Report will be published fortnightly, with a short summary of activity provided in alternate weeks.  Should activity increase again the report will return to a weekly schedule.  The next full report will be published on Thursday 18 March 2010.

More information about the indicators used in this report can be found on the HPA website

Summary for 11 March 2010 (Week 10)

• Pandemic influenza activity is low and generally stable or decreasing across the UK.
• In week 09 (ending 07 March), the weekly influenza/influenza-like illness (ILI) consultation rate decreased in England (RCGP weekly influenza-like illness consultation rate decreased from 9.0 to 6.3 per 100,000), remained stable in Scotland (ILI rate 33.7 in week 08 and 33.5 per 100,000 in week 09) and increased slightly in Nothern Ireland (combined influenza and ILI rate increased from 14.3 to 18.5 per 100,000) and Wales (GP consultation rate for influenza increased from 2.4 to 5.2 per 100,000) (figure 1). The QSurveillance rate decreased from 8.9 to 6.9 per 100,000.  In all schemes, the rate remains below the baseline level.

  Figure 1: Weekly GP influenza/influenza-like illness consultation rates in the UK.

  
• A decrease in respiratory syncytial virus (RSV) detections has been observed recently.  The RCGP consultation rate for acute bronchitis was stable overall (81.3 per 100,000 in week 09) though an increase was observed in people aged under 5 years (from 168.7 to 209.8 per 100,000).

  Figure 2: Weekly number and proportion of specimens collected through GP sentinel virological schemes positive for influenza (England only).

  
• 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.  The proportion of specimens collected through GP sentinel systems that are positive for influenza has decreased and is at a low level (3.4%, figure 2).
• Forty of 5,462 pandemic viruses tested have been confirmed to carry a mutation which confers resistance to the antiviral drug oseltamivir; three 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 447 deaths reported due to pandemic (H1N1) 2009 in the UK; 332 in England (to 04 March), 69 in Scotland, 28 in Wales and 18 in Northern Ireland (to 10 March).
• 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.
• In the temperate zone of the northern hemisphere, transmission of virus persists in some areas of Europe and Asia but influenza activity is declining and at low level in the most areas. The most active areas of transmission are currently observed in parts of Southeast Asia and East and South-eastern Europe. Several West African countries are increasingly reporting pandemic influenza cases, though surveillance data from the area is quite limited.  Recently, influenza type B is increasingly reported in Asia.  Globally 41% of all influenza detections were type A and 59% were influenza B, compared to 52% influenza B in the previous week.