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Respiratory Syncytial Virus (RSV) Season, U.S., 2011-2012

Respiratory syncytial virus (RSV) is the most common cause of severe lower respiratory tract disease among infants and young children worldwide. Currently there is no effective vaccine against RSV. However, palivizumab (say "pah-lih-VIH-zu-mahb"), a drug that contains virus-fighting antibodies to RSV, can help prevent severe RSV disease, such as pneumonia (inflammation of the lungs) or bronchiolitis (inflammation of the small airways in the lungs) in high-risk infants or young children. Since these antibodies are given to protect high-risk infants or young children only during yearly RSV outbreaks in their community, monitoring patterns of outbreaks has helped physicians determine when palivizumab should be given.

Outbreaks of RSV occur each year, usually lasting 4 to 5 months during the fall, winter, or spring. However, the exact timing of the RSV season can vary by region, as shown in this chart containing laboratory data from the United States National Respiratory and Enteric Virus Surveillance System (NREVSS)1. Of the 10 U.S. Department of Health and Human Services (HHS) regions (listed by region number and headquarter city)2 and Florida, the 2011-12 RSV season3 started and ended the earliest in Florida (mid-August to early March). Florida also had the longest RSV season (30 weeks). The start date of RSV season in other regions ranged from late October to mid-January, and the end date ranged from early March to early May.

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Learn more about RSV and how to protect yourself and your child.

Within a region, the timing of RSV season can change each year. Compared with 20114, the season started earlier in 2012 in all regions that are reporting data except one (Region 3). (Region 8 had not started the RSV season as of January 7, 2013). The table below compares the start dates of the RSV season in 2011 and 2012. The regions and states are listed in order from the earliest to latest RSV season start date.

HHS Region
(headquarter city) or State2
States Included in RegionStart of RSV Season
20112012

Florida

FL

Mid-August

Late July

Region 3 (Philadelphia)

DE, DC, MD, PA, VA, WV

Late October

Late October

Region 2 (New York)NJ, NYMid-NovemberEarly November

Region 6 (Dallas)

AR, LA, NM, OK, TX

Mid-November

Late October

Region 1 (Boston)

CT, ME, MA, NH, RI

Early December

Late November

Region 4 (Atlanta)

AL, GA, KY, MS, NC, SC, TN

Early December

Early November

Region 5 (Chicago)

IL, IN, MI, MN, OH, WI

Early December

Late November

Region 9 (San Francisco)

AZ, CA, HI, NV

Mid-December

Early November

Region 10 (Seattle)

AK, ID, OR, WA

Late December

Mid-December

Region 8 (Denver)

CO, MT, ND, SD, UT, WY

Early January

*

Region 7 (Kansas City)

IA, KS, MO, NE

Mid-January

Late November

Source:

CDC. Morbidity and Mortality Weekly Report. Respiratory Syncytial Virus Activity—United States, July 2011-January 2013. MMWR. 1 March 2013:141-144

Endnotes:

  1. CDC does not make recommendations regarding the administration of RSV immune prophylaxis. For additional information, contact NREVSS by email: mailto:nrevss@cdc.gov.
  2. HHS region (headquarter city): Region 1 (Boston): Connecticut, Maine, Massachusetts, New Hampshire, Rhode Island, and Vermont; Region 2 (New York City): New Jersey and New York; Region 3 (Philadelphia): Delaware, District of Columbia, Maryland, Pennsylvania, Virginia, and West Virginia; Region 4 (Atlanta): Alabama, Georgia, Kentucky, Mississippi, North Carolina, South Carolina, and Tennessee (data from Florida excluded); Region 5 (Chicago): Illinois, Indiana, Michigan, Minnesota, Ohio, 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. See http://www.hhs.gov/about/regionmap.html Idaho, Maine, Nebraska, New Mexico, Rhode Island, Utah, Vermont, and Wyoming did not have any participating laboratories in the 2011-12 season analysis.
    * The 2012-13 season onset occurred by December 15, 2012, in all regions except Region 8 (Denver).
  3. As defined by NREVSS, the RSV season starts when the first of two consecutive weeks during which the mean percentage of specimens testing positive for RSV antigen is ≥10%. The RSV season ends when the last 2 consecutive weeks during which the mean percentage of positive specimens is ≤10%.
  4. CDC. Morbidity and Mortality Weekly Report. Respiratory Syncytial Virus—United States, July 2011—January 2013. MMWR. 1 March 2013:141-144

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