We can define epidemiology as the study of the determinants and a distribution of health-related states. We will study how a pathogen, such as the common flu or the influenza AH1N1, is spread within a population. This is particularly important because an outbreak can cause severe human and economic losses, as with the Spanish flu of 1918, which killed 40 million people globally. Take a look at the following screenshot:

We can use the Center for Disease Control (CDC) data, which is freely available from their website. With these time series, we can perform statistical methods for descriptive epidemiology or causal inference. The CDC data is obtained using typical surveys and medical reports, providing real results.

We can use the dashboard for CDC Flu Trends and its data, which is freely available from the following link:

http://gis.cdc.gov/grasp/fluview/fluportaldashboard.html

Seasonal influenza (flu) data can be found at http://www.cdc.gov/flu/.