Respiratory syncytial virus surveillance in the United States, 2007-2012: results from a national surveillance system

Abstract

Background: Annual respiratory syncytial virus (RSV) outbreaks throughout the US exhibit variable patterns in onset, peak month of activity and duration of season. RSVAlert, a US surveillance system, collects and characterizes RSV test data at national, regional, state and local levels.

Methods: RSV test data from 296 to 666 laboratories from 50 states, the District of Columbia and Puerto Rico (as of 2010) were collected during the 2007-2008 to 2011-2012 RSV seasons. Data were collected in early August/September to the following August/September each season. Participating laboratories provided the total number and types of RSV tests performed each week and test results. RSV season onset and offset were defined as the first and last, respectively, of 2 consecutive weeks during which the mean percentage of specimens testing positive for RSV was ≥10%.

Results: Nationally, the RSV season onset occurred in October/November of each year with offset occurring in March/April of the following year. The RSV season averaged 20 weeks and typically occurred earliest in the South and latest in the West. The onset, offset and duration varied considerably within the U.S. Department of Health and Human Services regions. RSV activity in Puerto Rico was elevated throughout the 2-year period studied. Median onset in core-based statistical areas ranged from 2 weeks earlier to 5 weeks later than those in their corresponding states.

Conclusions: Substantial variability existed in the timing of RSV activity at all geographic strata analyzed. RSV actively circulated (ie, ≥10%) in many areas outside the traditionally defined RSV epidemic period of November to March.

FIGURE 1.

Proportions of RSV tests that were positive over 5 seasons, 2007–2008 through 2011–2012. Data from August 13 to August 6 of the following year are displayed for each season. If data collection for the RSVAlert program began or ended outside those weeks within a given season, data from those weeks are not displayed.

FIGURE 2.

RSV season characteristics based on RSV antigen, PCR and virus isolation test results, national level (including FL and PR). Black diamonds represent RSV season peak week.

FIGURE 3.

RSV season onset and offset range and median, national and HHS region levels* and FL, September 2007 to August 2012. HHS, US Department of Health and Human Services. Figure format source was taken from Mutuc and Langley. *Listed by region number and headquarters city. Region 1 (Boston): Connecticut, Maine, Massachusetts, New Hampshire, Rhode Island and Vermont. Region 2 (NY): New Jersey and NY. Region 3 (Philadelphia): Delaware, DC, Maryland, Pennsylvania, Virginia and West Virginia. Region 4 (Atlanta): Alabama, Georgia, Kentucky, Mississippi, North Carolina, South Carolina and Tennessee. Region 5 (Chicago): Illinois, Indiana, Michigan, Minnesota, OH and Wisconsin. Region 6 (Dallas): Arkansas, Louisiana, New Mexico, Oklahoma and Texas. Region 7 (Kansas City): Iowa, Kansas, Missouri and Nebraska. Region 8 (Denver): Colorado, Montana, North Dakota, South Dakota, Utah and Wyoming. Region 9 (San Francisco): Arizona, California, Hawaii and Nevada. Region 10 (Seattle): Alaska, Idaho, Oregon and Washington.

FIGURE 4.

RSV activity in PR during the 2010–2011 and 2011–2012 seasons.

FIGURE 5.

RSV season onset and offset range and median, CBSA level. *Median onset and offset ranges overlap.