Via the Public Health Agency of Canada, the January 3 update to its Influenza - Infectious Diseases page. Excerpt:
Influenza activity in Canada has continued to increase since late-November 2013, consistent with the usual timing of the seasonal influenza epidemic. Influenza A(H1N1)pdm09, which first emerged in 2009, causing the 2009 influenza pandemic, has continued to circulate as a seasonal influenza virus strain and has emerged as the predominant virus this season to date, in both laboratory detections and paediatric and adult hospitalizations.
Of the laboratory confirmed influenza-associated hospitalizations reported for the month of December 2013, the majority (99%) were associated with influenza A. Of the cases that were subtyped (n=254), 96% were associated with A(H1N1)pdm09.
By age group, influenza-associated hospitalizations were highest among adults 20-64 years of age (approximately 53%), followed by children under 5 years of age (22%), adults 65 years and older and adults 20-44 years of age. Of the influenza-associated ICU admissions and deaths reported in December 2013, the majority were due to A(H1N1)pdm09 in the 45-64 year old age group. Please refer to FluWatch for up-to-date information on influenza activity in Canada.
The United States is experiencing a similar influenza season with A(H1N1)pdm09 circulating and causing severe respiratory illness among young and middle-aged adults, many of whom were infected with A (H1N1) pdm09.
Of the influenza viruses antigenically characterized to date at the National Microbiology Laboratory (NML), all influenza A viruses and the majority of influenza B viruses were similar to the strains recommended by the WHO for the 2013-14 seasonal influenza vaccine, indicating that the vaccine is a good match to the circulating influenza viruses.