Flu season is off to a late but deadly start this year, according to CNN, which cites several measures for tracking the illness, including federal and trendy online tracking data.

One intriguing, but unorthodox, way to discern flu activity is the new Google Flu Trends, which follows Internet searches on the flu, rather than actual cases, like the nation’s authority for flu information, the U.S. Centers for Disease Control and Prevention. Google lists Colorado’s activity as moderate to high at a time when four toddlers–two in the Denver area and two more on the Western Slope–have lost their lives.

7News quotes Dr. Ken Gershman at the Colorado Department of Public Health and Environment as saying the deaths might have been prevented if the children had been fully vaccinated. It’s too early to know if the flu season is going to be severe in Colorado, Gershman says.