CDC releases RSV data

CDC. MMWR. 2011;60(35):1203-1205.

Trends in national respiratory syncytial virus activity have remained relatively stable during the most recent 4-year period, according to CDC data.

The current analysis compared the 2010-2011 respiratory syncytial virus (RSV) season with the previous four RSV seasons, which the researchers said included the period from July 2007 to June 2011.

The 2010-2011 RSV season onset occurred from mid-November to early January, and offset occurred from mid-March to April 30. These findings are from the 10 US Department of Health and Human Services regions but do not include Florida.

Onset for the previous four seasons ranged from mid-October to early January, and offset occurred from early February to early May.

Florida has an earlier onset and a longer duration of RSV than other parts of the country.

The current analysis involved only results of antigen detection methods, which were used by 98% of the laboratories participating in surveillance during the 4-year period. Also, only laboratories that conducted an average of at least 10 tests/week for at least 30 weeks/season were included.

Among 509 laboratories that reported at least 1 week of RSV testing, 179 labs from 42 states met inclusion criteria, according to the results. There were 50,860 positive results from 320,751 tests conducted during the study period.

The exact dates of the most recent national RSV onset occurred the week ending Nov. 20 and lasted 21 weeks, until the week ending April 9. The week ending Feb. 5 was determined to be the peak. When data from Florida were excluded, the national season onset occurred the week ending Nov. 27.

The median duration of the RSV season for the 10 regions was 19 weeks (range, 13-22 weeks), with the Boston area (region 1) having the shortest season and the Atlanta area (region 4) having the longest.

From July 2007 to June 2011, the average number of laboratories with data that met the inclusion criteria was 208 (range, 179-240). National onset occurred from mid-October to mid-November, with each individual season having an onset within 3 weeks of the median for the four seasons. The national offset occurred from mid-March to early April, with each season offset occurring within 2 weeks of the national median.

The median season duration was 21 weeks (range, 19-22 weeks), with mid-January as the median peak week.

The findings for the 4 years changed slightly when Florida was excluded from the analysis. Onset came around mid-October and lasted as late as early May. “Each region had individual season onset and offset dates within 5 weeks on either side of the median onset and offset,” the researchers wrote.

The shortest season duration was 13 weeks, and the longest was 23 weeks. The peak ranged from mid-December to early February.

Data for all regions indicated that the most recent season onset and offset began during the same week or later than the onset during 2007-2008.

These data correlate with data for hospitalizations due to RSV. They also aid in timing immunoprophylaxis activities with palivizumab (Synagis, MedImmune).

H. Cody Meissner

Data from the National Respiratory and Enteric Virus Surveillance System (NREVSS) play an important role in the formulation of Guidelines from the AAP for use of palivizumab (Synagis, MedImune) for RSV prophylaxis. This report describing the 2010-2011 RSV season demonstrates that onset, peak, offset and duration of RSV activity showed little variation from preceding seasons in each of 10 geographic regions within the United States. For most infants and young children who qualify for five monthly doses of palivizumab, at least 24 weeks of protective serum palivizumab levels will be provided. Administration of the first dose in early November and the fifth and final dose in early March will provide protective serum levels into May. These NREVSS data describing the most recent RSV season demonstrate that depending on an infant's risk factors, adherence to the recommendations for either five monthly doses of prophylaxis or for prophylaxis for the first 90 days of life will ensure optimal coverage for most areas within the United States. Complete recommendations are available at Pediatrics 2009;124:1694-17014.

H. Cody Meissner, MD
Infectious Diseases in Children Editorial Board member

Disclosure: Dr. Meissner reports no relevant financial disclosures.

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