WHO issues conclusions from 2011-2012 flu season

The World Health Organization recently released a report detailing its findings about the 2011-12 influenza season in the Northern Hemisphere.

The WHO reported that in most temperate countries in the Northern Hemisphere, the flu season started later than usual, except in North Africa, and was mild in most countries, according to CIDRAP News.

The WHO report, which appeared in its Weekly Epidemiological Record, said that the circulating flu strains this season varied widely by country and by region. In North America, the 2009 H1N1 strain was predominant in Mexico, but H3N2 was dominant in the United States and influenza B most prevalent in Canada.

In the temperate parts of Asia, influenza B peaked in China and Mongolia, only to be followed by a later rise in H3N2 activity. The reverse pattern was identified in South Korea and Japan.

Most countries saw doctors visits for flu-like symptoms below the levels of last season. Japan, on the other hand, reported its highest number of flu cases since 2002, except for during the pandemic period in 2009, CIDRAP News reports.

European countries, in particular, France and Spain, reported excess H3N2-related mortality rates in older adults. European officials also said the 2009 H1N1 virus was overrepresented in severe influenza cases.

The WHO report noted little resistance to Tamiflu in the 2009 H1N1 cases, except in 16 cases that appeared in Texas late in the season. Among the 14 cases with information available, three patients had used the drug for a day or more at the time specimens were collected, and two had family members taking the drug. Nine had no exposure to the medication.