How are the flu activity levels determined?
For each country or region where we have access to historical flu data, Flu Trends compares the estimates based on search data against a historical baseline level of flu activity for that area. Depending on whether the current estimate is higher or lower than the baseline, Flu Trends reports the general activity level as Minimal, Low, Moderate, High, or Intense. Each category has a corresponding color that is displayed under the graph.
