ATLANTA - The 1999-2000 respiratory syncytial virus (RSV) season is off and running, with reported widespread community outbreaks packing doctors' offices, emergency rooms and intensive care units with sick infants and children.
According to recently published figures in the Mortality and Morbidity Weekly Report the duration of the 1998-1999 RSV season was longer than previous years, with outbreaks reported after the unofficial close of the RSV season in several western and mid-western states. This season, preliminary surveillance data shows widespread RSV activity between July 1 and Nov. 12, 1999, predominately in communities in the southern United States.
"We've already seen a heavy RSV burden in the Atlanta area," said Alan Cohen, MD, assistant professor of pediatrics at Morehouse School of Medicine and director of clinical research at Georgia Pediatric Pulmonology Associates. "This winter we're having at least as bad a season as we've had in the past."
RSV infection peaks during the winter months and is the most common cause of lower respiratory tract disease in infants and children worldwide.
In the United States, RSV activity is monitored by the National Respiratory and Enteric Virus Surveillance System (NREVSS), a voluntary, laboratory-based system. About 80 labs encompassing 48 states participate in NREVSS, with 72 labs reporting on RSV. NREVSS reports trends to help identify when and where outbreaks occur, said Sara Lowther, surveillance coordinator, Centers for Disease Control and Prevention (CDC). The data is available on the CDC's Web site (www.cdc.gov/ncidod/dvrd/nrevss).
"Overall, NREVSS has helped us understand the epidemiology of community outbreaks of RSV," said Lowther, "and has provided ways to identify the start of outbreaks and alert public health staff or pediatricians when the onset of outbreaks will occur."
According to a recent study published in The Journal of the American Medical Association, bronchiolitis-associated hospitalizations of children younger than 5 have increased from 12.9 per 1,000 in 1980 to 31.2 per 1,000 in 1996. The increase in hospitalizations may be partly attributed to better detection of mild-to-moderate degrees of lower oxygen saturation in the blood, according to David Shay, MD, medical epidemiologist, Respiratory and Enteric Viruses Branch, CDC. Shay also attributed the increase in hospitalizations to the rise in the number of children going into daycare centers at an earlier age.
"There are a few things we don't believe are associated," said Shay. "We don't believe RSV is becoming more virulent, nor is there a single strain that goes across the United States each year like influenza. It's not due to the virus becoming `worse.'"
Serious complications exist, however, in infants and children in high-risk categories, including premature infants and babies with bronchopulmonary dysplasia. Also at an increased risk are children of multiple births, children sharing a bedroom, children in a school, group or daycare setting, children with congenital heart disease and children exposed to second-hand smoke. Minorities in urban settings, especially males of low socioeconomic status, are also at risk for greater difficulty with RSV.
For most full-term infants or otherwise healthy children younger than 1, RSV results in a mild upper respiratory infection. One in 10 will develop acute bronchiolitis. Most of these children can still be managed at home, but nearly 2% of infants will be hospitalized at some point with RSV bronchiolitis during the first year of life.
"Symptoms are more prominent in children by virtue of sheer anatomy. There's even a difference between infants and older children," said Cohen. "It doesn't take a lot of inflammation to have a more significant impact on the dynamics and effectiveness of breathing and oxygenating in the youngest, smallest children. That's really what makes infants younger than 3 months and preemies a higher risk."
Maureen Doolan Boyle, executive director of Mothers of Supertwins, said since almost all multiple birth children are premature, they are automatically at risk for RSV. "If you have one baby you're bringing to the hospital with a strong possibility of RSV, it would probably be advisable to have every one tested because it is so contagious," said Boyle.
In an effort to prevent high-risk babies from contracting RSV, Boyle recommended parents teach all family members proper hand washing methods before touching the babies; discouraging friends or relatives from coming over if they have a cold or flu-like symptoms; and staying away from crowded places and avoiding smokers. Boyle even recommended asking a smoker to change his or her shirt before touching high-risk babies.
The monoclonal antibody palivizumab (Synagis, MedImmune) is the only preventative medication available for high-risk children, according to Cohen, who conducted a study using the drug on 320 children last winter. Cohen said palivizumab has no impact on any other live vaccines, which has been a problem in the past with other prophylactic agents against RSV, such as RSV-IVIG (RespiGam, MedImmune). "And its side effect profile is actually no different from placebo," said Cohen.
For more information:
- CDC. Update: Respiratory Syncytial Virus Activity - United States, 1998-1999 Season. MMWR 1999;48(48):1104-6,1115.
- Shay DK, Holman RC, Newman RD, et al. Bronchiolitis-associated hospitalizations among U.S. children, 1980-1996. JAMA. 1999;282(15): 1440-1446.
- The RSV Impact Study Group. Palivizumab, A humanized RSV monoclonal antibody, reduces hospitalization from RSV infection in high-risk infants. Pediatrics. 1998;102(3):531-37.
- Cohen AH, Bonzer R, Montgomery GL, et al. A single center retrospective analysis of palivizumab use, a humanized RSV monoclonal antibody, in 320 high-risk pediatric patients during the 1998-1999 viral respiratory season. Chest Supplement 2. 1999;116(4):3425.
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