FIGURE WO-12 Number of specimens positive for influenza by subtype, Northern Hemisphere, April 19 to August 29, 2009 (weeks 17–35). Bars represent the number of specimens reported positive for influenza viruses during the reporting week represented in the x-axis. The x-axis also shows the number of countries that reported to FluNet during the respective week. Example: 17 (38) means that in week 17, 38 countries reported. The right side y-axis shows the proportion (percentage) and the left y-axis shows the absolute number of specimens reported positive for influenza viruses (influenza A subtypes, pandemic H1N1, and influenza B).
SOURCE: Fukuda (2009).