HPA Weekly National Influenza Report 13 August 2009 (Week 33)

Pandemic influenza activity continues to decrease across all regions of the UK and in all age groups, though remains at levels higher than expected for this time of year.

· In week 32 (week ending 09 August), the GP consultation rates decreased in England to just above the baseline thresholds. In Wales the rate decreased, though was still above the baseline threshold.

· The National Pandemic Flu Service (NPFS) continues to issue antiviral drugs to people with an

influenza-like illness who call or log onto the internet site. There has been a general decrease in the number of assessments, and antiviral collections, over the past week.

· Interpretation of data to produce estimates on the number of new cases continues to be subject to a considerable amount of uncertainty with the move to National Pandemic Flu Service (NPFS). HPA modelling gives an estimate of 25,000 (range 15,000 – 60, 000) new cases in England in week 32 compared to an estimated 30,000 cases in the previous week. The estimated number of new cases has decreased in all regions and age groups.

· 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 through sentinel and non-sentinel surveillance. No antiviral-resistant strains have been detected in the UK to date. Three drift influenza A (H3N2) variants have been identified in the UK.

· The majority of pandemic influenza cases continue to be mild. The cumulative number of deaths reported due to pandemic (H1N1) 2009 in the UK is 49. There was a total of 908 new patients hospitalised with suspected pandemic influenza in week 32 (up to 8am Monday 03 August); a decrease of 341 from the previous week. The highest hospitalisation rates have consistently been in the under 5-year age group. Hospitalisation rates have decreased over the past week in all age groups.

· According to the European Centre for Disease Prevention and Control (ECDC), by 12 August,

219,681 laboratory confirmed cases of pandemic influenza (H1N1) had been reported globally with 1882 deaths. In week 31, Malta reported high influenza activity, while other all other European countries reported low or moderate levels.