H1N1 Pandemic Update by Who

As reported by WHO - As of 11 October 2009, worldwide there have been more than 399232 laboratory confirmed cases of pandemic influenza H1N1 2009 and over 4735 deaths reported to WHO.

As many countries have stopped counting individual cases, particularly of milder illness, the case count is significantly lower than the actually number of cases that have occurred. WHO is actively monitoring the progress of the pandemic through frequent consultations with the WHO Regional Offices and member states and through monitoring of multiple sources of data.

Influenza activity continues to increase in the northern temperate zones across the world. In North America, the United States is now experiencing nationwide rates of Influenza-Like Illness (ILI) well above seasonal baseline rates with high rates of pandemic H1N1 2009 virus detections in clinical laboratory specimens. Canada is reporting increases in ILI rates for the third straight week with some provinces now crossing the baseline. Mexico also reports high intensity and active transmission in some areas of the country. Western Europe and northern Asia are experiencing increased rates of ILI, well above baseline in some countries but activity is generally not as widespread as in North America. Of note, nearly half of the influenza viruses detected in China are seasonal influenza A (H3N2) viruses, which appeared prior to and is co-circulating with pandemic H1N1 2009 virus.

The tropical zones continue to have transmission that is mixed as some countries have now peaked and are declining, while others are experiencing increases. In the tropical region of the Americas, several Caribbean Island nations are now reporting increased rates of illness while Brazil, Costa Rica and other countries on the continent are declining. In South Asia, most countries now report a decline in rates of illness.

Influenza rates in the temperate zones of the Southern Hemisphere have all returned to below baseline levels and very few detections of pandemic H1N1 2009 virus are being reported.

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

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