Background: The Centers for Disease Control and Prevention’s (CDC) Influenza Division collects and analyzes influenza surveillance data year-round and produces a weekly report on U.S. influenza activity during the influenza season which begins at week 40 each year. The U.S. influenza surveillance system provides information in five categories collected from eight data sources. The 2013-2014 influenza season began on September 29, 2013, and this report also summarizes influenza activity during the summer weeks of the 2012-13 season.

The five categories and eight components of influenza surveillance are:

• Viral Surveillance: U.S. World Health Organization (WHO) collaborating laboratories, the

National Respiratory and Enteric Virus Surveillance System (NREVSS), and human infection

with novel influenza A virus case reporting;

• Mortality: 122 Cities Mortality Reporting System and influenza-associated pediatric deaths;

• Hospitalizations: Influenza Hospitalization Network (FluSurv-NET) including the Emerging

Infections Program (EIP),

• Outpatient Illness Surveillance: U.S. Outpatient Influenza-like Illness Surveillance Network

(ILINet);

• Geographic Spread of Influenza: state and territorial epidemiologists’ reports.

Stephen B. Thacker CDC Library collection

United States