As of 2nd May, more than 214 countries and overseas territories or communities worldwide have reported laboratory confirmed cases of pandemic influenza H1N1 2009, including over 18,001 deaths. The World Health Organization (WHO) is actively monitoring the progress of the pandemic through frequent consultations with WHO Regional Offices and Member States, and through the monitoring of multiple sources of information.
The most active areas of pandemic influenza virus transmission are currently in parts of West Africa, the Caribbean, and Southeast Asia. In the temperate zone of the northern and southern hemisphere, overall pandemic influenza activity remains sporadic. Seasonal influenza virus type B continues to be detected sporadically across Asia, Africa, Europe, and the Americas, however, low levels of late season virus circulation have primarily been detected in East and Central Asia, southern Europe, and central Africa.
In the tropical zone of the Americas, limited data suggests that the pandemic influenza virus transmission remains active in several countries. In Central America, Guatemala reported three consecutive weeks of an increasing trend of respiratory diseases activity associated with regional spread of pandemic influenza virus and detection of severe cases. In Cuba, detections of pandemic virus and numbers of severe cases have increased since late March, however overall pandemic influenza activity may have recently peaked, according to the WHO. Although the overall intensity of respiratory diseases across the region remained low to moderate during April 2010, for short periods of time, circulation of pandemic influenza virus was reported to widespread (in Cuba and Barbados) or regional (in Mexico, Honduras, Nicaragua, Columbia, Venezuela, Brazil, Ecuador and Bolivia).
In Southeast Asia, the pandemic influenza virus continues to actively circulate in several countries of the region; however, respiratory disease trends in the region are variable. In Malaysia, limited data suggests that pandemic influenza virus transmission persists with ongoing reports of new cases (including severe cases) and media reports of several school outbreaks, particularly during late April and early May 2010. In Singapore, the national level of respiratory illnesses has been steadily increasing since early April 2010 and now exceeds the epidemic threshold; 37 per cent of sentinel respiratory specimens tested positive for influenza during the most recent tests. In Thailand, the proportion of sentinel outpatients with influenza-like illnesses and sentinel inpatients with pneumonia testing positive for pandemic influenza virus infection has declined significantly since peaking during late March 2010.
In Europe, overall influenza activity remained low with very low level co-circulation of pandemic and seasonal influenza type B viruses. The overall proportion of sentinel respiratory samples testing positive for influenza remained stable at about 5.3 per cent; and the total number of sentinel influenza B virus detections continued to exceed that of influenza A viruses, primarily due to low level seasonal influenza type B virus circulation in the Russian Federation and Kazakhstan.