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Trends and Surveillance

Respiratory syncytial virus (RSV) is the most common cause of lower respiratory tract infections among young children in the United States and worldwide. Most infants are infected before age 1, and virtually everyone gets an RSV infection by age 2.

Each year, on average, in the United States, RSV leads to—

  • 132,000 to 172,000 hospitalizations among children younger than 5 years old
  • 100,000 to 126,000 hospitalizations among children younger than 1 year old
  • 1.5 million outpatient visits among children younger than 5 years old
  • 177,000 hospitalizations and 14,000 deaths among adults older than 65 years

In climates with changing seasons like the United States, RSV infections occur primarily during late fall, winter, and early spring.

RSV Seasonal Trends

CDC analyzes data on RSV activity at the national, regional, and state levels, collected by a surveillance system called the National Respiratory and Enteric Virus Surveillance System (NREVSS).

For 2011 to 2012, the RSV season onset ranged from late October to mid-January, and season offset ranged from early March to early May in all 10 U.S. Department of Health and Human Services (HHS) regions, except Florida. Florida is reported separately because it has an earlier RSV season onset and longer duration than the rest of the country (see figure).

For data reported as of January 7, 2013, RSV onset for the 2012 to 2013 season occurred in all but one of the HHS regions by December 15, 2012. Seasonal patterns remained consistent with previous years.

Surveillance Systems

Information on cases and outbreaks of RSV infection is collected in the United States using the National Respiratory and Enteric Virus Surveillance System (NREVSS). This is a voluntary, laboratory-based surveillance system that was established in 1989 to monitor trends in several viruses, including RSV. NREVSS tracks the number of RSV tests that are done by participating laboratories and the proportion that are positive, by specimen type, location, and when they were collected. Serotyping, demographic data, and clinical data are not reported. Data from NREVSS provides information to public health officials and healthcare providers about the presence of RSV in their communities.