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Pandemic (H1N1) 2009 - update 83

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Weekly update

15 January 2010 -- As of 10 January 2009, worldwide more than 208 countries and overseas territories or communities have reported laboratory confirmed cases of pandemic influenza H1N1 2009, including at least 13554 deaths.

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 information.

Situation update:

The most intense areas of pandemic influenza virus transmission currently are in parts of North Africa, South Asia, and east and southeastern Europe.

In North Africa, limited data suggest that transmission of pandemic influenza virus remains active throughout the region, particularly in Morocco, Algeria, and Egypt. In West Asia, limit data suggest that pandemic virus continues to circulate widely with a number of countries likely having already experienced a peak in activity prior to December. Pandemic H1N1 2009 virus continues to be predominant circulating influenza virus in the northern African and western Asian regions with only sporadic detections of seasonal influenza viruses.

In South Asia, the northern and western parts of the subcontinent continued to experience active influenza transmission. In Nepal, increasing ARI activity and geographically regional to widespread influenza activity was reported during December and January. In India, overall activity may have peaked during mid to late December, however transmission has been regionally variable with a recently increasing trend in the western states, active but decreasing transmission in the northern states, and overall low activity in the eastern and southern states. In Sri Lanka, geographically widespread transmission with increasing trend of respiratory diseases was reported throughout December, however activity may have recently plateaued.

In Europe, pandemic influenza transmission remains geographically widespread throughout the continent, however, overall activity continued to decline substantially since November. A moderate intensity of respiratory diseases activity was reported in Romania, Ukraine, Turkey, and Switzerland, however, rates of ILI/ARI have been decreasing or have plateaued in all. At least four countries testing more than 20 sentinel respiratory specimens reported greater than 25% specimens were positive for influenza (Romania, Georgia, Germany, and France). The overall rate of specimens testing positive for influenza fell to 22% in Europe after reaching a peak of 45% during early November 2009. Pandemic H1N1 2009 virus continues to be predominant circulating influenza virus in the European region with only sporadic detections of seasonal influenza viruses.

In East Asia, influenza activity remains widespread but continues to decline overall. In Japan, influenza activity remains elevated but has declined since peaking at the end of November 2009. Although influenza transmission remains active and regionally variable in China, overall activity has declined substantially since peaking during mid November 2009 in northern and southern China. In Hong Kong SAR (China), influenza activity remained stably elevated but substantially lower than a large peak of activity during late September and early October 2009. In Mongolia, rates of ILI have been elevated above seasonal baseline since late October 2009 but declined substantially since a peak of activity was observed during November 2009. In DPR Korea, geographically regional influenza activity with increasing respiratory diseases trend was reported during early January 2010. Pandemic H1N1 continues to be the predominant circulating virus in the region but seasonal H3N2 viruses continue to circulate in very small numbers in northern China.

In the Americas, both in the tropical and northern temperate zones, overall pandemic influenza activity continued to decline or remain low. In North America, peak influenza activity occurred during early, mid, and late October in Mexico, the United States, and Canada, respectively. Small areas of increased influenza activity may be occurring in central and northern Mexico.

In temperate regions of the southern hemisphere, sporadic cases of pandemic influenza continued to be reported without evidence of sustained community transmission. This suggests that the level of population immunity in areas that experienced intense, high-level transmission during a winter season is high enough to prevent sustained transmission from recurring during the summer when the virus is less transmissible.

The Global Influenza Surveillance Network (GISN) continues monitoring the global circulation of influenza viruses, including pandemic, seasonal and other influenza viruses infecting, or with the potential to infect, humans including seasonal influenza. For more information on virological surveillance and antiviral resistance please see the weekly virology update (Virological surveillance data, below).