Cross Sectional Survey of Influenza Antibodies before and during the 2009 Pandemic in Shenzhen, China
Figure 1
The total number of ILI cases in each month of 2009 in Shenzhen.
In 2009, the peak of ILIs occurred in July 2009, sharply declined afterwards and formed a new wave in November. This may partially explain the significant drop in the three seasonal influenza antibody titer levels in September compared to March.