Notice how the orange CDC ILI timeseries moves for several weeks after it is initially rendered.

FORBES: How Accurate Is Google Flu Trends?

ILI-activity can have significant regional variation, so regional ILInet data was used as the target.

FORBES: How Accurate Is Google Flu Trends?

In Fall of 2009, we did just that and retrained a model using CDC ILI data from 2003 through summer of 2009 as the target.

FORBES: How Accurate Is Google Flu Trends?

For example, as of January 15th the New York City Department of Health and Mental Hygiene has daily ILI Emergency Department visit data through January 14th.

FORBES: How Accurate Is Google Flu Trends?

ILI-activity also varies significantly from season to season, both in its timing and severity, so we used ILInet data from 2003 to the most recent data points available at the time.

FORBES: How Accurate Is Google Flu Trends?