Pandemic (H1N1) 2009 - update 91

Pandemic (H1N1) 2009 - update 91
Weekly update
12 March 2010 -- As of 7 March 2010, worldwide more than 213 countries and overseas territories or communities have reported laboratory confirmed cases of pandemic influenza H1N1 2009, including at least 16713 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 active areas of pandemic influenza transmission are currently in Southeast Asia, however, lower levels of pandemic virus circulation persist in other parts of Asia and in Eastern and South-eastern Europe. In West Africa, limited data suggests that pandemic influenza virus transmission may be increasing in region. Of note, seasonal influenza B viruses have been increasingly detected in Asia and appear to be spreading westward.

In Sub-Saharan Africa, limited data suggests that on-going community transmission of pandemic influenza virus continues to increase in parts of West Africa, without clear evidence of a peak in activity. Increased detections of pandemic influenza virus have been observed among sentinel surveillance sites in several countries, including Senegal and Cote D'Ivoire, however, to date, data is limited regarding the spectrum of clinical severity of cases. Recent increases in influenza activity have also been reported in Rwanda. Much of eastern and southern Africa likely experienced an earlier peak in pandemic influenza activity during November 2009 and late summer 2009, respectively.

In South and Southeast Asia, pandemic influenza virus circulation persist in most countries, however, overall transmission remains most active in Thailand, especially since mid January 2010. Approximately half of all provinces in Thailand reported that greater than 10% of all outpatients sought care for ILI, and approximately 25% of all patients with ILI at sentinel sites tested positive for influenza. The current increase in the number of cases in Thailand remains well below an earlier period of peak transmission during June through September 2009. In Bangladesh, an increasing trend in respiratory disease was reported, however, overall influenza activity remains low. In India, influenza virus transmission persist at lower levels in the western region of India, while activity in other regions has largely subsided.

In East Asia, pandemic influenza activity continues to decrease or remain low as levels of ILI return to seasonal baselines in Japan and in the Republic of Korea. In Mongolia, a recent sharp increase in ILI activity was associated predominantly with a resurgence of circulation of seasonal influenza B viruses. In China, pandemic influenza activity has declined since peaking during November 2009, however, overall influenza activity remains elevated, largely due to an increase in the circulation of seasonal influenza B viruses.

In North Africa and Western Asia, overall pandemic influenza activity remains low in most places, with the exception of Iraq and Afghanistan, both of which reported regional spread of influenza with an increasing trend in respiratory diseases activity. In Afghanistan, a moderate impact on the healthcare system was reported in association with increased respiratory diseases activity. Although overall influenza activity remains low in Iran, all recent influenza virus detection have been due to seasonal influenza B viruses.

In Europe, overall pandemic influenza transmission continued to decline as low levels of pandemic virus continue to circulate in parts of eastern and south-eastern Europe. The overall percentage of sentinel respiratory specimens testing positive for influenza remained low (6.8%) but slightly increased compared to the previous week. Pandemic H1N1 2009 virus continues to be the predominant circulating influenza virus in the European region with the exception of the Russian Federation and Sweden where influenza B was reported as co-dominant or dominant.

In the northern and the southern temperate zones of the Americas, overall pandemic influenza transmission remained low as influenza virus continued to circulate at low levels. In Central America, Nicaragua and Honduras, reported slight increases in respiratory diseases activity, possibly due to an increase in school outbreaks; however, it is unclear to what extent the increases are associated with circulation of pandemic influenza virus. In Brazil, an increasing trend of respiratory diseases with low overall intensity was reported in association with regional spread of influenza virus.

In the temperate zone of the southern hemisphere, overall influenza activity remained low, with sporadic detections of pandemic and seasonal influenza viruses.

Although pandemic influenza virus continues to be the predominant circulating influenza virus worldwide, circulation of seasonal influenza B viruses continue to increase and spread across Asia, parts of Eastern Europe, and Eastern Africa, but most notably in China, Mongolia, Iran and the Russian Federation.

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).
http://www.who.int/csr/don/2010_03_12/en/index.html