FIGURE 4.

Percentage of all deaths attributable to pneumonia and influenza (P&I), by surveillance week and year — 122 U.S. Cities Mortality Reporting System, United States, 2008–2013*

* For the reporting week ending February 9, 2013.

^† The epidemic threshold is 1.645 standard deviations above the seasonal baseline.

^§ The seasonal baseline is projected using a robust regression procedure that applies a periodic regression model to the observed percentage of deaths from P&I during the preceding 5 years.