SAGE | 5 April 2011 1 |

Current Global Epidemiology

of Seasonal Influenza

April 2011

North America

Canada

USA

Mexico

Pneumonia and Influenza Mortality for 122 U.S. Cities

Source: FluView: http://www.cdc.gov/flu/weekly/

Epidemic  Threshold  

Seasonal  Baseline  

2007   2008  2006   2009   2010  

4

6

8

10

30 40 50 10 20 30 40 50 10 20 30 40 50 10 20 30 40 50 10 20 30 40 50 10 Weeks

% o

f All

Dea

ths

Due

to P

&I

SAGE | 5 April 2011 5 |

Influenza Hospitalizations and Deaths Canada 2010/11

  2 paediatric deaths: 1 between 6-23 months old, 1 10 – 16 years

  519 lab confirmed pediatric hospitalizations –  82% influenza A; of subtyped A's 83% H3N2, 17% H1N1 –  18% were 0-5 month olds; 29% were 6-23 month olds

  849 adult hospitalized cases reported: –  97% influenza A. Of A's subtyped: 84% were H3N2 –  69% were aged 65 years or older; 45% were males.

  191 fatal cases –  96% flu A; of A's subtyped: 91% H3N2 –  79% 65 years of age or older; another 12% were 45 - 64 years old

SAGE | 5 April 2011 6 |

Risk Factor data, US 2010/11 Season

Source: FluView: http://www.cdc.gov/flu/weekly/

Europe and

Asia

Western Europe

Eastern Europe

East Asia

Severe Case Data from the UK

  560 fatal influenza cases in the UK reported to the HPA (474 in 2009/10) –  92% of 536 (with data) were associated with H1N1 (2009) –  7% with influenza B

  Amongst the 539 cases with information on age: –  8% < 15 years; –  70% from 15 to 64 years –  22% older than 64 years of age

  69% of 480 fatal cases with available data had ≥1 risk for vaccination. –  23% with respiratory disease including asthma –  19% with immunosuppression –  8 (2%) cases were pregnant

  72% of 178 were NOT vaccinated with seasonal vaccine this season

SAGE | 5 April 2011 11 |

67% of SARI were flu, 94% of flu were A

SAGE | 5 April 2011 12 |

North Asia

 Rates of ILI were lower in all countries in 2010/11 than in the previous season but similar in magnitude to previous years.

 Mongolia, proportion of hospitalizations due to pneumonia and the number of deaths due to pneumonia were less than 2009/10 season.

 Number of severe and fatal cases reported in China lower than previous season.

SAGE | 5 April 2011 13 | http://flu.cdc.gov.tw/public/Data/111915165371.pdf

Chinese Taipei

Surveillance & Virology

SAGE | 5 April 2011 14 |

Summary

  Mixed pattern of virus transmission in the northern hemisphere this past winter

–  H3N2 and B played a larger role in the Americas –  H1N1 and B more common elsewhere –  H1N1 associated with severe disease and deaths in Europe

  Season was more severe in some areas, notably the U.K., Ireland, and Greece, and strained ICUs in those countries

–  But was milder in Asia

  Pattern of H1N1 doesn't appear to have changed from 2009/10 –  Mostly mild cases with some very severe –  Age of severe cases considerably younger than with H3N2 –  Risk factors unchanged but still significant portion have none

•  Obesity seems to be more widely accepted as a factor

SAGE | 5 April 2011 15 |

Acknowledgements

 Special thanks to: –  Angus Nicholl, ECDC –  Richard Pebody, HPA –  Rakhee Palekar, Otavio Oliva, PAHO –  Josh Mott, Caroline Brown, EURO –  Jeff Partridge, Yuzo Arima, WPRO –  Estelle Arseneault, PHA Canada –  Scott Eperson, CDC USA