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I believe what they're plotting are keyword searches, not cases of flu as you suggest.

"We've found that certain search terms are good indicators of flu activity. Google Flu Trends uses aggregated Google search data to estimate flu activity"

so I guess what the graphs are showing is public interest in flu which, they argue, usually correlates pretty stongly with actual cases of flu. I wonder how this relationship will hold up in more less predictable media conditions we're seeing during the current pandemic.

Otherwise I totally agree though. I think the maps really show the weakness of automatically generating graphics from a generic toolkit rather than crafting them to be most appropriate to the task of illuminating particular data. Having said that, I'm sure the technology can and will be refined to address the criticisms.


Tom, that exactly what it is. There's been a good relationship in the past between searches and cases ("Detecting influenza epidemics using search engine query data", www.nature.com/nature/journal/v457/n7232/full/nature07634.html), but you're right in that it be interesting to see whether there's enough of a distortion from the publicity this time around.

Alex Cook


As stated by Tom, it's google searches that's being used here, not cases, so the y-scales would be totally different. As a consequence, I think it makes sense not to put a scale on the y-axis. In any case, since the current outbreak is a pandemic to which most/all people have no immunity, there are going to be far more people infected (say, 3 times) this year than usual. So the plot would look silly even if it were cases that were being used.

You mention that the case data should be available to inform the public. In an ideal world, yes, but in many countries case data may be mandated by government and hence patients don't provide informed consent (yes, to being included in a large aggregated number). So it might not be legally possible for the data to be provided by health departments, and what google are doing is an excellent alternative.

Tom Carden

I think Google are using search terms to indicate flu activity, so that's why the y-axis remains unlabeled. It's still search trends, not number of cases.

Sean Carmody

There's quite a big of Swine Flu data here, but since many areas are no longer consistently testing for swine flu, except in cases of hospitalisation, the data should be used with care.


They are correlating search terms and not cases as indicated by several readers.

Alex and Tom - unlabeling any axis is a fatal error in graphing. Think about maps with no scales. This is how we end up walking for hours thinking that the two points look "close together" on the map. So I find it mystifying that Google insists on omitting the vertical scale.

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