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Laboratory-Based Surveillance for Rotavirus -- United States, July 1997-June 1998

Rotavirus infections are the leading cause of severe gastroenteritis among infants and young children worldwide (1,2). Each year in the United States, rotavirus causes an estimated 2.7 million cases of gastroenteritis among children aged less than 5 years, resulting in approximately 500,000 outpatient clinic and emergency department visits and 49,000 hospitalizations (3,4). In addition, rotavirus accounts for an estimated $264 million in health-care costs and approximately $1 billion in total medical and nonmedical costs (3). The large disease burden and cost associated with rotavirus have led to the development of rotavirus vaccines. In August 1998, the first live attenuated rotavirus vaccine (Rotashield{registered} {Wyeth Lederle Vaccines and Pediatrics}) * was approved for use in infants by the Food and Drug Administration. The Advisory Committee on Immunization Practices has recommended that this vaccine be given as a three-dose schedule to infants aged 2, 4, and 6 months. Since 1991, rotavirus activity in the United States has been prospectively monitored by the National Respiratory and Enteric Virus Surveillance System (NREVSS), a voluntary, laboratory-based system (5). This report summarizes surveillance data from NREVSS during the 1997-1998 rotavirus season and reviews issues related to rotavirus surveillance that are important for a national rotavirus vaccine program.

From July 1997 through June 1998, 66 laboratories in 41 states participated in NREVSS. Each laboratory reported weekly to CDC the number of stool specimens tested and the number positive for rotavirus by antigen-detection and electron microscopy methods. Of 22,912 fecal specimens examined, 5343 (23%) were positive for rotavirus. Seasonal increases in rotavirus detection were noted throughout the United States, and the timing of peak rotavirus activity varied by geographic location. Activity peaked first in the Southwest during November-December 1997 and last in the North and Northeast during April-May. Temporal and geographic trends during the July 1997-June 1998 reporting period varied slightly from trends during previous years (5), with late-season peaks in some laboratories in the western United States. Laboratories in Montana, Nevada, and Washington reported peak rotavirus activity during April, and an additional laboratory in Nevada reported peak activity during May, substantially later than the usual December-January peak for these sites. Data from Alaska and Hawaii were not available.

Reported by: National Respiratory and Enteric Virus Surveillance System collaborating laboratories, National Rotavirus Strain Surveillance System collaborating laboratories; Viral Gastroenteritis Section, Respiratory and Enteric Viruses Br, Div of Viral and Rickettsial Diseases, National Center for Infectious Diseases, CDC.

Editorial Note

Editorial Note: Rotavirus causes seasonal peaks of gastroenteritis each year in the United States, and the temporal and geographic patterns observed during the July 1997-June 1998 reporting period were generally characteristic of trends noted during previous years (5). The late-season (April-May 1998) peaks reported by laboratories in the southwestern United States is unusual and, so far, unexplained. The annual seasonal peaks of activity and the proportion of total specimens positive for rotavirus noted in this surveillance system are consistent with data collected from other temperate countries (6).

Surveillance systems for rotavirus are particularly important as a means to measure the impact of the licensure of the first rotavirus vaccine for use in U.S. infants. NREVSS is the largest, nationally representative system for surveillance of rotavirus infections in the United States (5). Participating laboratories transmit reports to CDC weekly by using an automated telephone reporting system, which allows for timely analysis of rotavirus activity. NREVSS has been an important tool for characterizing the geographic and temporal trends of rotavirus infections in the United States, and its findings have been validated by disease-based surveillance studies (4,7,8). Initiation of a new vaccine program against rotavirus gastroenteritis will generate additional surveillance needs, such as the capability for monitoring rotavirus strain prevalences and assessing disease burden over time. Although the implications for the potential effectiveness of the vaccine are unclear, these findings highlight the importance of laboratory-based surveillance to monitor for the emergence of novel or unusual rotavirus strains following the introduction of the new vaccine. In addition, disease-based rotavirus surveillance systems will be initiated during the 1998-99 rotavirus season to monitor the effectiveness of rotavirus vaccine programs.

To monitor rotavirus strain circulation in the United States, CDC, in collaboration with state and local public health laboratories, established the National Rotavirus Strain Surveillance in 1996 (9). During November 1996-May 1997, 10 laboratories submitted rotavirus-positive stool specimens to CDC for strain characterization. During this period, the four rotavirus strains that predominate worldwide and that are represented in the licensed vaccine accounted for 83% of isolates tested. However, 9% of strains characterized had not been detected previously in the United States and are not represented in the current vaccine. The implications for the potential effectiveness of the vaccine are unclear.

NREVSS will continue to monitor for changes in the epidemiology of rotavirus following implementation of a vaccine program, and will provide a foundation for expansion of U.S. strain surveillance. The combination of NREVSS, strain surveillance, and disease-based surveillance will make it possible to monitor the impact of the new vaccine program.


  1. De Zoysa I, Feachem RG. Interventions for the control of diarrhoeal disease among young children: rotavirus and cholera immunization. Bull World Health Organ 1985;63:569-83.

  2. Glass RI, Kilgore PE, Holman RC, et al. The epidemiology of rotavirus diarrhea in the United States: surveillance and estimates of disease burden. J Infect Dis 1996;174:S5-S11.

  3. Tucker AW, Haddix AC, Bresee JS, Holman RC, Parashar UD, Glass RI. Cost-effectiveness analysis of a rotavirus immunization program for the United States. JAMA 1998;279:1371-6.

  4. Parashar UD, Holman RC, Clarke MJ, Bresee JS, Glass RI. Hospitalizations associated with rotavirus diarrhea in the United States, 1993 through 1995: surveillance based on the new ICD-9-CM rotavirus-specific diagnostic code. J Infect Dis 1997;177:13-7.

  5. Torok TJ, Kilgore PE, Clarke MJ, Holman RC, Bresee JS, Glass RI. Visualizing geographic and temporal trends in rotavirus activity in the United States, 1991 to 1996. Pediatr Infect Dis J 1997;16:941-6.

  6. Cook SM, Glass RI, LeBaron CW, Ho M-S. Global seasonality of rotavirus infections. Bull World Health Organ 1990;68:171-7.

  7. Jin S, Kilgore PK, Holman RC, Clarke MJ, Gangarosa EJ, Glass RI. Trends in hospitalizations for diarrhea in United States children from 1979-1992: estimates of the morbidity associated with rotavirus. Ped Infect Dis J 1996;15:397-404.

  8. Ho M-S, Glass RI, Pinsky PF, Anderson LJ. Rotavirus as a cause of diarrheal morbidity and mortality in the United States. J Infect Dis 1988;158:1112-6.

  9. Ramachandran M, Gentsch JR, Parashar UD, et al. Detection and characterization of novel rotavirus strains in the United States. J Clin Microbiol 1998;36:3223-9.

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