Symptoms of an epidemic: measuring the flu season

Chances are, if you live in North America, you know someone who has been sick with the flu recently. The spread of influenza is a seasonal concern for healthcare workers in the United States. Although many people contract and spread influenza throughout the year, flu season typically begins in late November or early December and spikes early in the following year. A year ago, in January 2014, nearly ten percent of all deaths in the U.S. were flu- or pneumonia- related. Several signs indicate that this current flu season may be even more severe than the last, due in part to a less-effective vaccine. (Note that it’s still important to get vaccinated for the flu every year!)

The Centers for Disease Control leads national influenza surveillance that tracks multiple aspects of the spread of the flu each season, including the strain of the flu and how it affects the population. This surveillance helps healthcare workers track the severity of the flu and respond accordingly. The two measures we have on PolicyMap are visits to health centers for flu-like illness (flu activity) and the geographic spread of the disease – whether epidemiologists consider it to be sporadic, locally concentrated, regional, or widespread.

Here is how flu activity changed from October 2014 to December 2014:

The dramatic increase in flu activity is nothing new for this time of year, but it’s important for those interested in public health to know where clusters of activities are located. Both these measures are reported to CDC and updated in the FluView website on a weekly basis, though for simplicity, we aggregate them to both month and season. We’ve updated the data as of December and will add another update before the end of the flu season. Check out more of our influenza data in the Health menu!