Friday, October 16, 2009

WHO H1N1 Situation Update 70, October 16, 2009

The most recent WHO situation update discusses current distribution and spread trends of pandemic H1N1 around the globe. As usual, surveillance information may be an underestimation, as most countries have stopped counting and investigating all individual cases.

The update also highlights three articles of interest published this week in the peer reviewed literature, that reported three different series of seriously ill pandemic influenza patients in Canada, Mexico, Australia, and New Zealand. Several important observations were made including:

• A significant portion of patients with severe disease requiring intensive care had no predisposing conditions. The numbers are not directly comparable as the studies categorized conditions differently but nearly 1/3 of ICU patients in Australia and New Zealand had no predisposing conditions. 98% of ICU cases in Canada had a comorbid condition, which in this report included hypertension, smoking, and substance abuse, but only 30% had comorbid conditions that were considered "major". In Mexico, 84% of critical patients had an underlying condition, which in the report included hypertension, ever having smoked, and hyperlipidemia, conditions that are not considered risk factors for severe influenza outcomes. All three groups were impressed by the number of severe cases occurring in previously healthy individuals.

• The researchers in Australia and New Zealand reaffirmed that infants under the age of 1 year have the highest risk of developing severe illness. The average age of ICU patients was 32, 40, and 44 years in Canada, Australia/New Zealand, and Mexico respectively.

• The study from Australia and New Zealand estimated that the demand for ICU beds due to viral pneumonia during the pandemic was as much higher than in previous influenza seasons. The Canadian study reported that intensive care capacity in Winnipeg, Manitoba, was "seriously challenged" at the peak of the outbreak with full occupancy of all regional ICU beds.

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