Google web search popularity of the disease names plus death, spread, victims and picture(s) in the 60 days after a public health emergency was declared.
Circles are sized by their Google popularity index, which indicates the relative popularity of a term compared to the three others over the time period.
A score of 100 represents the maximum popularity among the four terms in the time period for each disease respectively, while 0 is minimum.
*Laboratory confirmed cases are likely to underestimate the true disease burden, especially for the H1N1 epidemic. These counts should be considered conservative.