Vol. 20, No. 47
THE JOHNS HOPKINS MICROBIOLOGY NEWSLETTER
Tuesday, November 20, 2001
A. Provided by Karen Fujii,, Division of Outbreak Investigation, Maryland Department of Health and Mental Hygiene.
B. The Johns Hopkins Hospital, Department of Pathology. Information provided by Rob Law, M.D.
Case Description
A previously healthy 5 month old white female presented to the Pediatric Emergency department with a 4 day history of fever, cough, and clear rhinorrhea. On physical exam, the infant exhibited increased respiratory rate and retraction of the intercostal muscles. A chest radiograph displayed a bilateral interstitial infiltrate. A nasopharyngeal swab tested positive for Respiratory Syncytial Virus by direct immunofluorescence.
Respiratory Syncytial Virus
Introduction: Beginning in October and lasting through mid-spring is what is commonly known as RSV season. Belonging to the Paramyxoviridae, respiratory syncytial virus is an enveloped, spherical, negative-strand RNA virus measuring 120-300 nm.
Clinical features. The clinical manifestations of RSV include rhinitis, bronchiolitis, tracheobronchitis, and pneumonia. Causing seasonal epidemics, RSV is the major cause of lower respiratory tract illness in infants and young children. Most children recover in 8-15 days. In children with underlying complications such as congenital heart disease, bronchopulmonary dysplasia, and immunodeficiency, RSV may cause severe, life-threatening infection. Hospitalization is required in 0.5-2% of patients. Infectious respiratory droplets spread the virus, and many individuals have already experienced infection by RSV before the first few years of life. Pediatric wards may be a source of nosocomial spread of RSV.
Diagnosis. A direct immunofluorescence test for RSV antigen is available, and is reported to be 90% sensitive as compared to culture. RSV antigen may appear in the cytoplasm of cells within 8 hours of infection. Viral culture is performed in conjunction with the antigen test. The only acceptable specimen is a nasopharyngeal aspirate collected in viral transport media.
Management. In the management of severely affected infants, supportive care is critical. Studies examining the effect of steroids in the acute and convalescent stages have not shown any benefit. Ribavirin aerosol may be used in the treatment of some patients with severe disease. Some investigators have used a combination of immune globulin intravenous (IVIG) with high titers of neutralizing RSV antibody (RSV-IVIG) and ribavirin to treat patients with compromised immune systems. No vaccine is currently available. Prophylactic RSV-IVIG may be given to susceptible infants during RSV season.
Figure 1. Structure of human pneumoviruses such as RSV
References:
1. CDC website for respiratory viruses: www.cdc.gov/ncidod/dvrd/revb/respiratory/rsvfeat.htm
2. Harper, MB: Pediatric infectious disease emergencies. Curr Opin Pediatr. 1995; 7(3):302-8.
3. La Via, WV, Grant SW et al: Clinical profile of pediatric patients hospitalized with respiratory syncytial virus infection. Clin Pediatr. 1993; 32(8): 450-4
4. Mandell, Douglas, and Bennet: Principles and Practice of Infectious diseases. Fourth edition, 1995 Churchill Livingstone New York, pp1501-18.