Nosocomial respiratory syncytial virus infections.

We studied the frequency and severity of respiratory syncytial virus infections acquired nosocomially on an infants' ward during a community outbreak. Every three or four days all infants and staff were examined, and specimens were obtained for viral isolation. During two months, 14 of 44 contact infants acquired the virus. All were ill, and four had pneumonia. Infected infants had a significantly longer mean hospital stay (21.5 days) than uninfected ones (9.2 days, P less than 0.001). Risk of nosocomial infection could not be related to age or to underlying disease, but was linked to length of hospitalization: 45 per cent of infants hospitalized for one week or more became infected, and the percentage increased with length of stay. Ten of 24 staff members also acquired the virus and appeared to play a major role as virus carriers. Nosocomial respiratory syncytial virus infection poses a major risk for hospitalized infants and adds to hospital costs.     

Evaluation of five methods for respiratory syncytial virus detection.

A total of 117 nasal aspirates were cultured for respiratory syncytial virus (RSV) and tested for RSV antigen by a direct fluorescent-antibody (DFA) test (Bartels Immunodiagnostic Supplies, Inc., Bellevue, Wash.), the Directigen enzyme immunoassay (EIA; Becton Dickinson Microbiology Systems, Cockeysville, Md.), the TestPack EIA (Abbott Laboratories, North Chicago, Ill.), and RSV EIA (Abbott). Agreement of two of five methods or a positive RSV culture were required to validate a result. A total of 57 of 117 (48.7%) specimens were culture positive in HEp-2 cells, A549 cells, or both. A total of 5 of 117 (4.3%) additional specimens met the criteria of a positive specimen; i.e., 62 of 117 (53.0%) specimens were positive. Results obtained from 77 of 117 (65.8%) specimens were concordant for all five methods. The sensitivities, specificities, and positive and negative predictive values for the culture and DFA methods were 91.9, 100, 100, and 91.7% and 91.9, 96.4, 96.6, and 91.4%, respectively. The sensitivities, specificities, and positive and negative predictive values for the three EIA procedures, Directigen, TestPack, and RSV EIA, were 75.8, 80.0, 81.0, and 74.6%; 93.6, 100, 100, and 93.2%; and 71.0, 100, 100, and 75.3%, respectively. New self-contained EIA configurations and the DFA method offer attractive alternatives to the culture method. Technical simplicity, rapid turnaround time, performance, and cost must all be considered when selecting a system for RSV detection.     

Innate immune responses in respiratory syncytial virus infections

Respiratory syncytial virus (RSV) is the most important viral respiratory pathogen of early life. Studies of the immune response in general (and the innate response in particular) to this agent are of interest for a number of reasons. First, severe forms of illness may be a result of enhanced immunologic responsiveness to viral constituents at the time of infection. Secondly, the immune response to RSV may consist principally of innate immune responses at the time of maximum severity of illness. Third, RSV infection in infancy may be linked via immune mechanisms to the development of childhood wheezing. Finally there are no meaningfully effective forms of therapy for RSV infection, and elucidation of the immune response may suggest new therapeutic approaches. This review will summarize our current knowledge of innate immune responses to RSV infection. Specifically we will review early interactions of the virus with surfactant proteins and Toll-like receptors, chemokine release from infected cells, cytokine release from activated inflammatory cells, activation of neuroimmune pathways, generation of dendritic cells, the release of soluble mediators of airway obstruction, and genetic polymorphisms associated with RSV-related illness.     

Rapid diagnosis of respiratory syncytial virus infections in immunocompromised adults.

Although rapid antigen detection methods for the documentation of respiratory syncytial virus (RSV) infections are widely used with pediatric patients, these tests have not been prospectively evaluated in immunocompromised (IC) adults. For bone marrow transplant recipients and adult patients undergoing chemotherapy for leukemia who had recent onset of respiratory symptoms, respiratory samples (combined nasal wash [NW]-throat swab [TS], endotracheal tube [ET] aspirate, or bronchoalveolar lavage [BAL] samples) were collected for simultaneous culture and rapid antigen detection with the Directigen test kit (Becton Dickinson, Cockeysville, Md.). NW specimens from hospitalized pediatric patients with suspected RSV infection were also evaluated. Viral quantitation was performed on aliquots of the original specimens. A total of 539 samples from 372 adult patients were evaluated. RSV was isolated from 56 specimens (40 NW-TS, 7 ET aspirate, and 9 BAL specimens). By using culture as the "gold standard," rapid antigen detection had a sensitivity of 15% for adult NW-TS specimens, 71.4% for ET aspirate specimens, and 88.9% for BAL specimens; the specificity was > or = 97% for all specimen types. Significantly greater viral quantities were present in pediatric NW specimens than in adult NW specimens. In adults, more virus was present in BAL and ET aspirate specimens than in NW-TS specimens. Rapid detection of antigen respiratory samples obtained from the lower respiratory tracts of IC adults is sensitive and specific, but detection in upper respiratory tract samples is insensitive. The lower sensitivity of antigen detection in NW-TS specimens may be due to decreased viral load. A BAL specimen is more sensitive than an NW-TS specimen for the rapid diagnosis of RSV disease in IC adults.     

Rapid immunoperoxidase assay for detection of respiratory syncytial virus in nasopharyngeal secretions.

Samples of nasopharyngeal secretions obtained from 70 infants and young children with acute respiratory disease were examined for the presence of respiratory syncytial virus by immunoperoxidase assay (IPA). The IPA was compared with the immunofluorescence assay and with cell culture isolation. Respiratory syncytial virus antigen-positive cells were detected by both IPA and immunofluorescence assay in 28 specimens; 25 samples were positive in cell culture. The agreement between virus isolation and IPA and IFA was 89%. The applicability of IPA to rapid viral diagnosis of respiratory syncytial virus infection is discussed.     

Detection, pathogenesis, and therapy of respiratory syncytial virus infections.

Respiratory syncytial virus (RSV) infection is a major cause of serious lower respiratory disease in infancy and early childhood. The unique pathogenesis of lower respiratory illness due to RSV offers some intriguing clues to the role of the human immune system in both protection against and development of respiratory illness. More than any other virus, rapid diagnostic techniques have been especially successful in identifying RSV infection. Many of these techniques could be easily adaptable to diagnosis of influenza virus infection and other agents. Finally, ribavirin therapy of RSV infection represents one of the few instances in which antiviral therapy has been shown to be effective for respiratory illnesses. Fundamental observations in these areas in the case of RSV infection open up new and exciting pathways for investigation of respiratory infection due to other viral, chlamydial, and mycoplasmal agents.     

Hyperimmune globulins in prevention and treatment of respiratory syncytial virus infections.

Respiratory syncytial virus (RSV) is an important community and nosocomial respiratory pathogen for infants and young children. RSV causes especially severe disease in the prematurely born or those with chronic cardiopulmonary diseases. Elderly persons and those with T-cell deficiencies, such as bone marrow transplant recipients, are also at high risk for serious lower respiratory tract infections. To date, prevention of RSV infections by vaccination has proven elusive and no preventive drugs exist. Studies in animals and humans have shown that the lower respiratory tract can be protected from RSV infection by sufficient circulating RSV neutralizing antibody levels. Recently, an RSV hyperimmune immune globulin (RSVIG) was developed and tested for the prevention of RSV infections or reduction of disease severity. Passive immunization of high-risk children with RSVIG during the respiratory disease season effected significant reductions in RSV infections, hospitalizations, days of hospitalization, intensive care unit admissions, days in the intensive care unit, and ribavirin use. Studies in cotton rats and owl monkeys show that RSV infections can also be treated with inhalation of immune globulin at doses substantially smaller than required for parenteral treatment. Therapeutic trials of parenteral RSVIG have been completed and are pending analysis. The use of polyclonal, hyperimmune globulins and perhaps human monoclonal antibodies provides an additional approach to the prevention and perhaps the treatment of certain viral lower respiratory tract infections such as those caused by RSV.     

Rapid detection of respiratory syncytial virus with a monoclonal antibody.

We developed an indirect fluorescent-antibody test employing a mouse monoclonal antibody directed against the nucleoprotein of RSV for rapid detection of respiratory syncytial virus (RSV). This test demonstrated distinctive fluorescent inclusions in HEp-2 cells infected with 24 RSV isolates collected during 6 previous years but not in cells infected with 13 other respiratory viruses. Examination of nasal cells of 100 infants with acute respiratory illness showed that the indirect fluorescent-antibody test employing the monoclonal antibody was 79% sensitive and 100% specific, as compared with the combination of both culturing and a similar indirect fluorescent-antibody test with commercial anti-RSV serum. This monoclonal antibody is an easily produced, well-characterized, sensitive, and specific reagent for the rapid detection of RSV antigen.     

Comparison of the RSV respi-strip with direct fluorescent-antigen detection for diagnosis of respiratory syncytial virus infection in pediatric patients

The RSV Respi-Strip was compared to the SimulFluor respiratory screen for detecting respiratory syncytial virus in nasopharyngeal aspirates from pediatric patients. Of samples tested, 115/239 (49%) were positive by direct fluorescent-antigen detection. The sensitivity and specificity of the RSV Respi-Strip were 92% (95% confidence interval [CI], 86% to 96%) and 98% (95% CI, 94% to 100%), respectively, with a diagnostic efficiency of 95%.     

Diagnostic efficacy of two rapid tests for detection of respiratory syncytial virus antigen.

With the availability of ribavirin therapy for serious respiratory syncytial virus (RSV) infections, rapid diagnostic tests for the detection of RSV antigen are increasingly important. Efficacies of a commercially available enzyme immunoassay (EIA) (Abbott Laboratories, North Chicago, Ill.) and a fluorescent-antibody assay (FA) were evaluated in a study involving 135 specimens from children with respiratory symptoms. A nasal wash specimen was cultured immediately on RSV-sensitive A549 cells; the nasal wash was also used for EIA. FA was performed on a nasopharyngeal swab specimen with bovine anti-RSV and anti-bovine immunoglobulin G antisera (Burroughs Wellcome Co., Research Triangle Park, N.C.). A total of 39 specimens (28%) were tissue culture positive, including 35 EIA-positive and 37 FA-positive samples (sensitivities, 90 and 95%, respectively). All 96 tissue culture-negative specimens were EIA negative (specificity, 100%); 94 of these 96 specimens were FA negative (specificity, 98%). Positive and negative predictive values for the tests were as follows: 100 and 96% for EIA, respectively, and 95 and 98% for FA, respectively. Other viruses, including influenza A virus, adenovirus, enterovirus, and herpes simplex virus, were isolated in nine cases. One adenovirus-positive specimen had a false-positive RSV FA result; all nine specimens were RSV EIA negative. Both tests performed well in our study and provide cost-effective alternatives to tissue culture. The RSV EIA, in particular, uses standard serologic techniques and equipment and does not require expertise in virology. More widespread availability of rapid diagnostic tests for RSV will hopefully result in early and appropriate use of antiviral therapy in patients at risk for serious RSV infections.     

Comparison of rapid diagnostic techniques for respiratory syncytial and influenza A virus respiratory infections in young children.

We performed virus isolation tests for respiratory viruses on combined nasal wash-throat swab specimens collected from infants and children with acute respiratory illnesses presenting to a hospital clinic during a 3-month period of concurrent epidemics of respiratory syncytial virus (RSV) and influenza A virus (Flu A) infections. Virus isolation results were used to assess the utility of commercially available rapid diagnostic kits for these two viruses. The kits employed direct immunofluorescence (IF) of cells (Imagen for RSV and Flu A), indirect IF of cells (Baxter Bartels Microscan), and enzyme immunoassay (EIA) (Becton Dickinson Directigen for RSV and Flu A and Abbott TestPack for RSV). All testing was completed on 81 specimens from 80 subjects. Of the 81 specimens, 53 (65%) yielded a virus: RSV, 28%; Flu A, 25%; rhinovirus, 6%; and enterovirus, cytomegalovirus, herpes simplex virus, and adenovirus, 2 to 4% each. Among the tests, Bartels Microscan and Directigen Flu-A exhibited the highest sensitivities (87 and 75%) and efficiencies (94 and 94%) for RSV and Flu A, respectively. All the tests exhibited high specificity. Thus, optimal detection of RSV and Flu A among infants and children who presented to a hospital clinic required two different detection methods (IF and enzyme immunoassay) and kits from two different companies (Baxter [Bartels Microscan] and Becton Dickinson [Directigen]).     

Nosocomial infections due to rotavirus and respiratory syncytial virus in pediatric wards: a 2-year study

Rotavirus and respiratory syncytial virus (RSV) infections represent up to 30% of the totality of nosocomial infections in paediatric wards. We studied the importance of these infections in the paediatric wards of the University Hospital Center of Poitiers, France, from October 1996 to September 1998. We defined as nosocomial an infection acquired after 3 days of hospitalization for rotavirus and after 7 days for RSV. The 274 cases of children presenting rotavirus gastroenteritis or RSV infection within this period were studied. Rotavirus was detected in stools by using an agglutination test and RSV was diagnosed in nasopharyngeal aspirations by direct examination with an immunofluorescence assay (IFA), cell culture and serotyping with IFA. We noted 50 rotavirus and 224 RSV infections, with a first epidemic of RSV subgroup B (49.5%) and a second epidemic of subgroup A (44.9%). 19 (38%) were rotavirus nosocomial infections and 5 (2.2%) were RSV nosocomial infections. The majority of the nosocomial infections occurred before the age of one year and particularly before the age of 6 months (42.2% for rotavirus, 60% for RSV). In comparison to community-acquired infections, children with rotavirus nosocomial infections were younger (9 months versus 12.5 months) which was the opposite for RSV nosocomial infections (10.8 months versus 6.5 months). The sex-ratio of children with community-acquired infections was 2.1 that was not reported in nosocomial infections. The length of stay in hospital was always longer in nosocomial infections (11.7 days versus 3.6 days for rotavirus; 38.8 days versus 4.8 days for RSV). Diarrhea (p = 0.007) and vomiting (p = 0.013) for enteric infections and wheezing (p = 0.02) for respiratory infections were more often observed in community-acquired infections. This study emphasizes the frequency and the consequences of rotavirus and RSV nosocomial infections in paediatric wards and the importance of the hygienic rules to prevent these infections.     

Human respiratory syncytial virus and other viral infections in infants receiving palivizumab.

BACKGROUND: Palivizumab is a humanized monoclonal antibody that prevents severe human respiratory syncytial virus (HRSV) infections. OBJECTIVES: We determined the etiology of respiratory viral infections in palivizumab recipients, and monitored the clinical outcome and HRSV genotype in HRSV-infected infants. STUDY DESIGN: Nasopharyngeal aspirates (NPAs) were collected from children receiving palivizumab who consulted or were hospitalized for acute respiratory tract infection (ARTI) during the 2004-2005 season. Viral cultures and multiplex RT-PCR for influenza A/B, HRSV and human metapneumovirus were performed. The fusion (F) gene of HRSV amplicons was also sequenced. RESULTS: Among 116 enrolled patients, 51 (44%) had > or = 1 episode of ARTI for a total of 93 visits. At least one virus was identified in 33 (36%) of the 93 NPA samples; HRSV accounted for 11 (33%) of confirmed viral etiologies. Compared to subjects who had other viral ARTI, HRSV-positive subjects had less fever (p=0.01) and tended to have more bronchiolitis (p=0.07). Ten subjects (11 visits) developed HRSV infection, although only one was hospitalized. HRSV was detected after a median of 5.5 palivizumab doses and a median of 14 days after the last dose. One of the 11 HRSV strains tested had a F mutation located in the palivizumab-binding site. CONCLUSION: HRSV is still a major cause of ARTI in children receiving palivizumab, although the outcome of infected children appears mild.