Lower Respiratory Tract Diseases Caused by Common Respiratory Viruses among Stem Cell Transplantation Recipients: A Single Center Experience in Korea

PURPOSE

To describe the incidence, clinical courses, and risk factors for mortality of lower respiratory tract diseases (LRDs) caused by common respiratory viruses (CRVs) in stem cell transplantation (SCT) recipients.

MATERIALS AND METHODS

We retrospectively reviewed the medical records of 1038 patients who received SCT between January 2007 and August 2011 at a single center in Korea.

RESULTS

Seventy-one CRV-LRDs were identified in 67 (6.5%) patients. The human parainfluenza virus (HPIV) was the most common causative pathogen of CRV-LRDs at 100 days [cumulative incidence estimate, 23.5%; 95% confidence interval (CI), 3.3-43.7] and 1 year (cumulative incidence estimate, 69.2%; 95% CI, 45.9-92.5) following SCT. The 30-day overall mortality rates due to influenza-LRDs, respiratory syncytial virus-LRDs, HPIV-LRDs, and human rhinovirus-LRDs were 35.7, 25.8, 31.6, and 42.8%, respectively. Co-pathogens in respiratory specimens were detected in 23 (33.8%) patients. The overall mortality at day 30 after CRV-LRD diagnosis was 32.8% (22/67). High-dose steroid usage (p=0.025), a severe state of immunodeficiency (p=0.033), and lymphopenia (p=0.006) were significantly associated with death within 30 days following CRV-LRD diagnosis in a univariate analysis. Multivariate logistic regression analysis revealed that high-dose steroid usage [odds ratio (OR), 4.05; 95% CI, 1.12-14.61; p=0.033] and lymphopenia (OR, 6.57; 95% CI, 1.80-24.03; p=0.004) were independent risk factors for mortality within 30 days of CRV-LRDs.

CONCLUSION

CRV-LRDs among SCT recipients showed substantially high morbidity and mortality rates. Therefore, the implement of an active diagnostic approaches for CRV infections is required for SCT recipients with respiratory symptoms, especially those receiving high-dose steroids or with lymphopenia.

Molecular investigations of an outbreak of parainfluenza virus type 3 and respiratory syncytial virus infections in a hematology unit

A large simultaneous outbreak of respiratory syncytial virus (RSV) and parainfluenza type 3 (PIV-3) infections occurred on an adult hematology unit. Implementation of enhanced infection control was complicated by cocirculation of the two different viruses, with prolonged viral shedding from infected patients, and placed great pressure on health care staff; of 27 infected hematopoietic stem cell transplant patients, 9 died, and the unit was closed for 2 months. Retrospective molecular investigation of the virus strains involved in the outbreak was performed by analyzing part of the fusion gene of PIV-3 and part of the glycoprotein gene of RSV. Reverse transcription-PCR on nasopharyngeal aspirates from patients infected before and during the simultaneous outbreak generated amplicons for sequence analysis. A single strain of RSV and a single strain of PIV-3 had spread from person to person within the unit; 7 patients were infected with RSV, 22 were infected with PIV-3, and 4 were infected with both viruses. The PIV-3 outbreak had started at the beginning of August 3 months before the RSV outbreak; it had arisen when PIV-3 was introduced from the community by a patient and passed to another patient, who became chronically infected with the identical strain and, in spite of being nursed in isolation, was most likely the source from which widespread infection occurred in November. Had these early cases been linked to a common PIV-3 strain at the time of diagnosis, enhanced infection control precautions might have prevented the eventual extensive spread of PIV-3, making it much easier to deal with the later RSV outbreak.

Parainfluenza type 3 infection post stem cell transplant: high prevalence but low mortality

Parainfluenza type 3 (PIV 3) is a well-recognized cause of respiratory illness after stem cell transplantation (SCT), with an estimated incidence of 2-7% and a high mortality rate associated with lower respiratory tract infection (LRTI). A 12-month retrospective study was undertaken in which 23 positive cases of PIV 3 occurred in SCT recipients. The frequency of infection was 36.1% in matched unrelated donor SCT recipients, 23.8% in sibling allogeneic SCT recipients and 2.3% in autologous transplant recipients. Seventeen cases were outpatient or community acquired despite standard infection control measures. Eleven patients only developed upper respiratory tract symptoms. LRTI symptoms developed in 12 patients, of whom eight had a new infiltrate on chest X-ray. Overall mortality at 30 days from PIV 3 diagnosis was 4% (one patient). Four patients died within 100 days of PIV 3 diagnosis, but PIV 3 was not believed to be the primary cause of death in any of these patients. Early ribavirin was used in eight patients and only one patient who received ribavirin died. These results suggest a higher prevalence of PIV 3 but a lower mortality than documented previously, particularly in allogeneic transplant recipients. The authors propose that the high prevalence reflects the unit's policy of active surveillance for respiratory viruses and the difficulty in preventing transmission of PIV 3, especially in the outpatient setting during an outbreak period. Ribavirin treatment may improve outcome in patients with LRTI but is not required in all patients with PIV 3.

Contamination of a specific-pathogen-free rat breeding colony with Human parainfluenzavirus type 3

Routine antibody surveillance for Sendai virus in a breeding colony suggested viral invasion into laboratory rats. A more specific haemagglutination-inhibition test implied that the agent was related closely to Human parainfluenza virus type 3 (hPIV3), rather than Sendai virus. To isolate this virus, Vero cells were inoculated with lung homogenates of 30 young animals from the colony. One of the cultures became positive at the second passage by RT-PCR directed to the hPIV3 NP and L genes. Cytopathic effect with cell fusion was observed at the third passage. The HN gene of this virus (KK24) had >93 % similarity to those of other hPIV3 isolates, suggesting a human origin of KK24. Experimental intranasal inoculation of KK24 into SD rats showed virus replication in the lungs at 3–5 days post-infection (p.i.). Pathological examination of the lungs at day 5 p.i. indicated a moderate detachment, degradation and apoptosis of bronchial epitheliocytes with peribronchial mononuclear infiltrations. At day 7 p.i., these changes became less prominent, and no lesions were apparent at day 10 p.i. or later. The infected rats seroconverted at day 7 p.i. On the contrary, none of the 30 experimentally infected ICR mice showed any pathological lesions in their lungs, despite seroconversion at 7 days p.i. These results suggest that hPIV3 can invade rat colonies and has a moderate and transient pathogenicity in rats. This is the first report of non-experimental hPIV3 infection in laboratory rats, unexpectedly detected by antibody screening for Sendai virus.

The novel parainfluenza virus hemagglutinin-neuraminidase inhibitor BCX 2798 prevents lethal synergism between a paramyxovirus and Streptococcus pneumoniae

An association exists between respiratory viruses and bacterial infections. Prevention or treatment of the preceding viral infection is a logical goal for reducing this important cause of morbidity and mortality. The ability of the novel, selective parainfluenza virus hemagglutinin-neuraminidase inhibitor BCX 2798 to prevent the synergism between a paramyxovirus and Streptococcus pneumoniae was examined in this study. A model of secondary bacterial pneumonia after infection with a recombinant Sendai virus whose hemagglutinin-neuraminidase gene was replaced with that of human parainfluenza virus type 1 [rSV(hHN)] was established in mice. Challenge of mice with a sublethal dose of S. pneumoniae 7 days after a sublethal infection with rSV(hHN) (synergistic group) caused 100% mortality. Bacterial infection preceding viral infection had no effect on survival. The mean bacterial titers in the synergistic group were significantly higher than in mice infected with bacteria only. The virus titers were similar in mice infected with rSV(hHN) alone and in dually infected mice. Intranasal administration of BCX 2798 at 10 mg/kg per day to the synergistic group of mice starting 4 h before virus infection protected 80% of animals from death. This effect was accompanied by a significant reduction in lung viral and bacterial titers. Treatment of mice 24 h after the rSV(hHN) infection showed no protection against synergistic lethality. Together, our results indicate that parainfluenza viruses can prime for secondary bacterial infections. Prophylaxis of parainfluenza virus infections with antivirals might be an effective strategy for prevention of secondary bacterial complications in humans.

Low mortality rates related to respiratory virus infections after bone marrow transplantation

Respiratory viruses (RVs) frequently cause severe respiratory disease in bone marrrow transplant (BMT) recipients. To evaluate the frequency of RV, nasal washes were collected year-round from BMT recipients with symptoms of upper respiratory tract infection (URI). Direct immunofluorescence assay was performed for respiratory syncytial virus (RSV), influenza (Flu) A and B, adenovirus and parainfluenza (Paraflu) virus. Patients with RSV pneumonia or with upper RSV infection, but considered at high risk for developing RSV pneumonia received aerosolized ribavirin. Oseltamivir was given to patients with influenza. A total of 179 patients had 392 episodes of URI. In all, 68 (38%) tested positive: RSV was detected in 18 patients (26.4%), Flu B in 17 (25%), Flu A in 11 (16.2%) and Paraflu in 7 (10.3%). A total of 14 patients (20.6%) had multiple RV infections or coinfection. RSV pneumonia developed in 55.5% of the patients with RSV-URI. One of the 15 patients (6.6%) with RSV pneumonia died. Influenza pneumonia was diagnosed in three patients (7.3%). RSV and influenza infections peaked in fall-winter and winter-spring months, respectively. We observed decreased rates of influenza and parainfluenza pneumonia and low mortality because of RSV pneumonia. The role of antiviral interventions such as aerosolized ribavirin and new neuraminidase inhibitors remains to be defined in randomized trials.

Parainfluenza virus 3 infection after stem cell transplant: relevance to outcome of rapid diagnosis and ribavirin treatment

All 456 recipients of hemopoietic stem cell transplants (SCT) at the Hammersmith Hospital, London, from January 1990 through September 1996 were reviewed for parainfluenza virus (PIV) infections. Of the 24 (5.3%) PIV type 3 (PIV3)-infected patients, 10 had upper respiratory tract infection and all survived, but 8 of 14 with pneumonia died. A same-day immunofluorescence test diagnosed PIV3 infection in 20 (83%) of the 24 cases, but virus culture diagnosed only 10 (42%) of the 24 cases after a mean delay of 12 days. Eighteen PIV3-infected patients first received ribavirin at a median of 3 days after onset of symptoms, but, nevertheless, 2 patients shed PIV3 for 4 months. Six of 10 patients with pneumonia died despite early ribavirin therapy. The cause of death was not established by autopsy; 3 patients had concurrent infections, but in 3, only PIV3 was detected. The value of immunofluorescence testing for early diagnosis and treatment of PIV3 infection after SCT is demonstrated, but the outcome was not altered.

Increased tumor necrosis factor-alpha (TNF-alpha) gene expression in parainfluenza type 1 (Sendai) virus-induced bronchiolar fibrosis

Increased airway resistance and airway hyperresponsiveness induced in rats by infection with parainfluenza type I (Sendai) virus is associated with bronchiolar fibrosis. To determine whether increased tumor necrosis factor (TNF)-alpha gene expression is an important regulatory event in virus-induced bronchiolar fibrosis, pulmonary TNF-alpha mRNA and protein expression was assessed in rat strains that are susceptible (Brown Norway; BN) and resistant (Fischer 344; F344) to virus-induced bronchiolar fibrosis. Virus-inoculated BN rats had increased TNF-alpha pulmonary mRNA levels (P < 0.05) and increased numbers of bronchiolar macrophages and fibroblasts expressing TNF-alpha protein compared with virus-inoculated F344 rats (P < 0.05). Virus inoculation also induced elevated TNF-alpha mRNA and protein levels (P < 0.05) in cultured rat alveolar macrophages (NR8383 cells). A 55-kd soluble TNF receptor-immunoglobulin G fusion protein (sTNFR-IgG) was used to inhibit TNF-alpha bioactivity in virus-inoculated BN rats. Treated rats had fewer proliferating bronchiolar fibroblasts, as detected by bromodeoxyuridine incorporation, compared with virus-inoculated control rats (P < 0.05). There was also increased mortality in p55sTNFR-IgG-treated virus-inoculated rats associated with increased viral replication and decreased numbers of macrophages and lymphocytes in bronchoalveolar lavage fluid (P < 0.05). The results of this study indicate that 1) Sendai virus can directly up-regulate TNF-alpha mRNA and protein expression in macrophages, 2) TNF-alpha is an important mediator of virus-induced bronchiolar fibrosis, and 3) TNF-alpha has a critical role in the termination of Sendai viral replication in the lung.

Protective effect of passive immunization against TNF-alpha in mice infected with Sendai virus

TNF-alpha has been reported to be induced in mice infected with Sendai virus. We evaluated the role of TNF-alpha in the virus infection. TNF-alpha was induced locally in proportion to virus titers in the lung. The activity was correlated with suppression of body weight gain. Passive immunization against TNF-alpha improved body weight gain and ameliorated pneumonic lesions in infected mice, and prevented them from lethal infection, but lung virus induced emaciation, pneumonic lesions and death were mediated by TNF-alpha.

Predictors of outcome of severe respiratory syncytial virus-associated respiratory failure treated with extracorporeal membrane oxygenation

OBJECTIVE

To examine the Extracorporeal Life Support Organization registry data base for all infants and children with respiratory syncytial virus-associated respiratory failure managed with extracorporeal life support, to delineate predictors of outcome.

DESIGN

Retrospective cohort study.

SETTING

Extracorporeal Life Support Organization data registry.

PATIENTS

All pediatric patients treated in the United States with extracorporeal life support for severe pediatric respiratory syncytial virus-associated respiratory failure reported to the registry, from 1982 through June 1992.

INTERVENTIONS

Venoarterial or venovenous extracorporeal life support.

MEASUREMENTS AND MAIN RESULTS

As of June 1992, fifty-three pediatric patients meeting study entry criteria were reported to the Pediatric Respiratory Failure Registry (n = 412) as having received extracorporeal membrane oxygenation (ECMO) for severe respiratory syncytial virus infection with pulmonary failure. Forty-nine percent (26/53) were successfully managed and survived to hospital discharge. The mean patient age was 5.0 +/- 8.6 months. Duration of mechanical ventilation before institution of extracorporeal life support was 8.1 +/- 6.2 days. Multivariate logistic regression analysis found four variables to be associated with patient nonsurvival at the p < 0.05 level: male gender, longer duration of mechanical ventilation before ECMO, higher peak inspiratory pressure, and lower ratio of arterial oxygen tension to fraction of inspired oxygen. Era of treatment was not associated with outcome. Receiver operator characteristic curve analysis of this multivariate model resulted in cutoff points of r = 0.5 and 0.1 that resulted in 92% sensitivity and 81% specificity (false-positive ratio 19%) and 96% sensitivity and 73% specificity (false-positive ratio 27%), respectively.

CONCLUSIONS

Predictors of outcome of severe respiratory failure caused by respiratory syncytial virus infection managed with ECMO exist, and multivariate predictive models with high sensitivity and low false-positive risk are possible. Similar mathematical models may be helpful in establishing criteria for future trials of ECMO versus conventional respiratory support.

Improved outcome of respiratory syncytial virus infection in a high-risk hospitalized population of Canadian children. Pediatric Investigators Collaborative Network on Infections in Canada

PURPOSE

To determine the outcomes in children at high risk for death or complications from respiratory disease who are hospitalized with respiratory syncytial virus (RSV) infection.

DESIGN

Retrospective chart review.

SETTING

Twelve pediatric tertiary care centers.

PATIENTS

All hospitalized children with an RSV infection diagnosed by a positive antigen detection test result or viral isolation during the study period from 1988 to 1991, encompassing three winter seasons. Charts from patients in the following high-risk groups were reviewed in detail: (1) congenital heart disease, (2) chronic lung disease, (3) immunodeficiency, (4) age less than 6 weeks, (5) gestational age less than 36 weeks, and (6) hypoxia (defined as oxygen saturation less than 90% or arterial oxygen pressure less than 60 mm Hg).

MEASUREMENTS

The age of all children, the date of RSV identification, and the use of oxygen supplementation, intensive care, and ventilatory support. In addition, the duration of these treatments and the duration of hospitalization were noted. Left-to-right shunting and pulmonary hypertension before RSV infection were determined in those children with congenital heart disease. The nature of the chronic lung disease was noted. Death within 2 weeks of RSV identification was recorded, and the use of ribavirin, bronchodilators, and corticosteroids was determined.

RESULTS

Significant year-to-year variation in the frequency of RSV infection was confirmed, with a peak during the 1989-1990 winter noted by the majority of centers (p = 0.0001). Of the 1584 patients in the study, 260 had underlying cardiac disease, 200 had chronic lung disease, 35 had compromised immune function, 378 had been premature, 373 were less than 6 weeks of age, and 338 had hypoxia. Seventeen patients died within 2 weeks (mortality rate 1%); significantly more patients with underlying cardiac disease (3.4%) or lung disease (3.5%) died. Immunocompromised patients had the longest hospital stay (median 39 days), followed by those patients with underlying cardiac or pulmonary disease (11 days); patients less than 6 weeks of age (5 days) and those with hypoxia (6 days) had the shortest hospital stays. Patients with underlying cardiac and pulmonary disease also required oxygen supplementation for a significantly longer period.

CONCLUSION

The year-to-year variation in frequency of RSV infection was confirmed in this study. Morbidity and mortality rates associated with RSV infection in a high-risk population in Canada were significantly lower than previously reported.

An outbreak of respiratory syncytial virus in a bone marrow transplant center

An outbreak of respiratory syncytial virus (RSV) infection occurred among 31 patients in a marrow transplant center over a 13-week period beginning in January 1990. RSV infection was also documented in 35 family members and employees. Of 18 patients with pneumonia, 14 (78%) died. None of 13 with upper respiratory infection died. Preengraftment patients tended to develop pneumonia more frequently than did engrafted patients. Early administration of ribavirin may have had a beneficial effect in patients with pneumonia. Antigenic and genomic analysis of 14 available isolates suggested that at least four different viral strains were responsible for the outbreak. One group of patients and 1 employee in spatial proximity were infected with the same strain and likely acquired their infections nosocomially. RSV infection in marrow transplant patients is a serious and life-threatening infection with a high mortality rate once pneumonia develops.

Serologic study of phocine distemper in a population of harbor seals in Scotland

A serologic survey of the prevalence of morbillivirus antibodies was conducted in a population of harbor seals (Phoca vitulina) from northeastern Scotland, where mortality was comparatively low during the 1988 phocine distemper virus outbreak. None of the 12 seals sampled before the epizootic were seropositive. Thirty-five (52%) of 68 seals sampled after the beginning of the epizootic were seropositive, although there were significant age-related differences in both the number of seropositive individuals and in antibody levels. Marking studies showed that most seropositive seals caught during the peak of the epizootic survived for several months. Thus, the low mortality observed in this population did not appear to result from a lack of contact with the virus.

Mass mortality in seals caused by a newly discovered morbillivirus

During a recent disease outbreak among harbour seals (Phoca vitulina) in the North and Baltic seas, more than 17,000 animals have died. The clinical symptoms and pathological findings were similar to those of distemper in dogs. Based on a seroepizootiological study, using a canine distemper virus (CDV) neutralization assay, it was shown that CDV or a closely related morbillivirus (phocid distemper virus-PDV) was the primary cause of the disease. The virus was isolated in cell culture from the organs of dead seals and characterized as a morbillivirus by serology (immunofluorescence neutralization and enzyme-linked immunosorbent assays) and by negative contrast electron microscopy. Experimental infection of SPF dogs resulted in the development of mild clinical signs of distemper and CDV-neutralizing antibodies. The disease was reproduced in seals by experimental inoculation of organ material from animals that had died during the outbreak. However, seals that had been vaccinated with experimental inactivated CDV vaccines were protected against this challenge. This fulfilled the last of Koch's postulates, confirming that the morbillivirus isolated from the seal organs, was the primary cause of the disease outbreak. The recent demonstration of the presence of a similar virus in Lake Baikal seals (Phoca sibirica), which infected these Siberian seals 1 year before the northwestern European seals were infected, raises new questions about the origin of this infectious disease in pinnipeds.

Association between respiratory syncytial virus outbreaks and lower respiratory tract deaths of infants and young children

The temporal patterns of respiratory virus isolations from 10 laboratories in the USA were compared with that of deaths of children less than 5 years old from July 1975 through June 1984. Isolations of respiratory syncytial virus (RSV) occurred as yearly winter outbreaks; parainfluenza virus 1 and 2 isolations occurred as well-defined outbreaks every other year in the autumn; parainfluenza virus 3 isolations occurred throughout the year with periodic, increased isolations suggestive of outbreaks; and influenza virus isolations (A, B, or A plus B) occurred as yearly winter outbreaks. After data were controlled for seasonal patterns, RSV isolations were strongly correlated with the winter peaks in lower respiratory tract illness (LRI) deaths of infants 1-11 months old; influenza virus isolations were correlated with the winter peak in LRI deaths of children 24-59 months old. The parainfluenza viruses were not correlated with respiratory deaths. This study supports the idea that RSV is a major contributor to winter peaks in LRI deaths of children 1-11 months old.

Use of extracorporeal membrane oxygenation in the treatment of respiratory syncytial virus bronchiolitis: the national experience, 1983 to 1988

In an effort to obtain data to provide the basis for the design of controlled clinical trials, we contacted all U.S. participants in the National ECMO Registry to assemble the national experience on the use of extracorporeal membrane oxygenation in respiratory syncytial virus bronchiolitis during the past 5 years. Twelve infants were treated at nine centers between 1983 and 1988. Eight had been born prematurely, and five had bronchopulmonary dysplasia. The mean age at onset of infection with respiratory syncytial virus was 108 +/- 102 days. The mean length of ventilator management before extracorporeal membrane oxygenation was 7.8 +/- 7.1 days. All infants had persistent hypoxemia with a mean arterial oxygen pressure of 39.2 +/- 11.7 torr (5.3 +/- 1.6 kPa) despite high ventilator pressures (mean airway pressure 19.7 +/- 6.4 cm H2O) and 100% inspired oxygen; six had air leak syndrome. Seven infants survived (58%). The mean duration of extracorporeal membrane oxygenation for survivors was 233 +/- 139 hours. Preexisting chronic lung disease did not predict a poor outcome: four of the five infants with bronchopulmonary dysplasia survived. Six of the survivors have subsequently achieved expected developmental milestones and one has slight motor delay. We conclude that, for infants with severe respiratory syncytial virus bronchiolitis whose condition deteriorates despite maximal ventilator management, extracorporeal membrane oxygenation may provide lifesaving support. The duration of successful treatment with this therapy may be longer than that for conventional neonatal indications, but excellent neurologic outcome may be expected in survivors.

Respiratory syncytial virus-induced acute lung injury in adult patients with bone marrow transplants: a clinical approach and review of the literature

Acute lung injury induced by respiratory syncytial virus (RSV) is a major cause of morbidity and mortality in patients who have undergone bone marrow transplantation. Twenty-nine of the 74 patients who received bone marrow transplants at the University of Minnesota during a 1-year period developed evidence of acute lung injury, and RSV was identified as the cause in 8. We discuss the clinical course of these 8 patients and offer a clinical approach to RSV infection occurring after bone marrow transplantation. We also review the immune response to infection with RSV and relate this information to the nature and degree of immunosuppression present in patients undergoing this type of transplantation. We found bronchoalveolar lavage with rapid antigen detection to be particularly useful for the prompt diagnosis of this serious infection. The virus was obtained from the lower respiratory tract of each patient and was identified in lavage effluent by culture and by antigen detection (ELISA). The mean time to a positive culture was 6 days, while detection of antigens of respiratory syncytial virus by ELISA was completed within 18 hours in all cases. The clinical progression of the illness in immunocompromised patients appears to be the same as in non-immunocompromised persons: upper respiratory tract infection and illness precede lower respiratory tract infection and acute lung injury. Seven of our 8 patients had upper respiratory tract symptoms or abnormal sinus radiographs, and upper respiratory specimens (cultures and ELISA from nasopharynx, throat, and sputum) were positive in 5 of 8 patients. Six patients developed RSV-induced lung injury before marrow engraftment; 4 of them had respiratory failure requiring mechanical ventilation and died, including 3 in whom RSV was eliminated from the lower respiratory tract following treatment with ribavirin aerosol. Two additional pre-engraftment patients had only relatively mild lung injury 4 days after beginning treatment with ribavirin for RSV infection in the upper respiratory tract. Their recovery suggests that early treatment may ameliorate RSV-induced lung injury. The remaining 2 patients developed lung injury after marrow engraftment. Both of these patients had clear chest radiographs, responded clinically to ribavirin, and survived. RSV is a potentially treatable cause of life-threatening lung injury, if the physician is aggressive in identifying the virus in the upper respiratory tract before evidence of lung injury appears. Rapid detection methods are essential when bone marrow transplant patients have fever along with signs, symptoms, or radiographic indications of nasal or sinus disorders.(ABSTRACT TRUNCATED AT 400 WORDS)

Analysis of the antibody response to bovine respiratory syncytial virus proteins in calves

The antibody response in calves to natural infections with bovine respiratory syncytial virus (BRSV) was analysed by radioimmunoprecipitation assays. Antibodies to virus proteins of Mr 200K (L), 87K (G), 46K (F1), 41K (N), 35K (P), 28K and 24K (F2), 27K (M), 22K and less than 14K could be identified. Recovery of 6- to 7-month-old calves from severe BRSV-associated disease was accompanied by the development of an antibody response to the virus, which was directed mainly o the F and N proteins. Calves of 2 to 3 weeks of age possessed moderate levels of maternal antibodies to BRSV particularly directed to the F and N proteins but became seriously ill after infection. The antibody response in these calves was severely suppressed. In the sera of 4- to 9-month-old calves that died in the course of infection, high antibody levels to the virus were found, which were directed at least to the F and N proteins. The presence or development of antibodies to the F and N proteins appears insufficient for protection against or recovery from BRSV infections.

[Virus excretion and changes in virulence of type 1 paramyxovirus of pigeons following passage through chickens]

Paramyxovirus type 1 of pigeons (strain PMV1-D) was transmitted by sequential contact over nine groups of SPF chicks. The first and last (9th) passages were made in 12-day-old SPF chicks, whereas the others were made in day-old chicks. Mortality was much higher in the last passage group than it was in the first group. None of the day-old chicks survived the PMV1-D infection. Increased virulence of PMV1-D for chickens following passages was also found to be present by the virus characterisation indexes, the EID50, the ICPI and the IVPI in particular.

Severe respiratory syncytial virus infection: clinical features, nosocomial acquisition and outcome

Respiratory syncytial virus (RSV) frequently causes bronchiolitis in young infants. RSV infection was established by culture, serologic response, immunofluorescence of secretions or lung tissue or typical histology on pathologic examination of the lungs in 10 patients who were hospitalized at Children's Medical Center, Dallas. Eight were infants 4 days to 3 months old, one was 9 months and one was 16 months old. Seven patients were afebrile but had rapidly progressive diffuse infiltrates on chest roentgenograms. Six infants admitted for surgical correction of gastrointestinal anomalies or congenital heart disease had tracheal intubation before onset of pneumonia. RSV infection was acquired in the hospital in five infants. Five patients developed chronic pulmonary changes and 8 of the 10 infants died. These observations emphasize the importance of nosocomial transmission of RSV and the frequency of fatal infection in children with congenital anomalies. They also suggest that intubation can be a predisposing factor and that RSV infection can lead to chronic pulmonary changes.

Effect of emulsifiers on influenza type A virus infection, in vivo and in vitro studies

Results of in vitro studies carried out by other investigators suggest that insecticide emulsifiers enhance the replication of animal viruses possessing a single-stranded RNA genome. Based on this observation and on epidemiological findings, it has been postulated that insecticide emulsifiers and related compounds may be etiologically involved in Reye's syndrome. Reye's syndrome is an enigmatic pernicious disease of childhood causally associated with an antecedent viral infection, usually influenza, and putatively associated with exposure to environmental chemicals. The present study was carried out to assess the effects of emulsifiers on infection in vivo with influenza type A virus, a virus possessing a single-stranded RNA genome, using the suckling mouse as host, and in vitro using a susceptible line of mammalian cells. Three coded emulsifiers retrospectively identified as Atlox 3409F, Toximul MP8, and Triton X-100 were assayed at concentrations of 1.0, 2.5, 5.0, and 10.0 ppm. None of the emulsifiers enhanced the plaquing efficiency of influenza A/PR/8/34 (HON1) virus in Madin-Darby canine kidney cells (less than a twofold increase), nor did percutaneous application of these emulsifiers at a concentration of 21 parts per thousand in peanut oil enhance the lethality of influenza A/PR/8/34 (HON1) virus infection. Indeed, peanut oil alone, and in combination with the emulsifiers, lowered lethality relative to mice that were treated percutaneously in parallel with physiologic saline.

Respiratory syncytial viral infection in infants with congenital heart disease

Occasional reports have suggested that infants with congenital heart disease may have an increased risk of severe illness from respiratory syncytial virus (RSV) infection. We prospectively studied 699 infants hospitalized during the winters of 1976 through 1980, when RSV was prevalent in the community; 229 of these infants had proved RSV infections acquired either before admission or during hospitalization; 27 had both congenital heart disease and RSV infection, and 46 had congenital heart disease without RSV infection. Infected infants with congenital heart disease had significantly more severe illness than those without congenital heart disease, as judged by the requirement for intensive care and assisted ventilation and by the mortality rate (37 per cent vs. 1.5 per cent, P less than 0.01). The infection was acquired nosocomially by 21 per cent of infected infants; the mortality rate from nosocomial infection was also higher in infants with congenital heart disease (44 per cent vs. 5 per cent, P less than 0.01). Pulmonary hypertension was the one condition particularly associated with severe RSV illness. Eight of the 11 infants (73 per cent) with congenital heart disease and pulmonary hypertension died during their RSV illness. The courses in infants with congenital heart disease with and without RSV infection were also compared. Their ages, types of cardiac lesions, and incidence of pulmonary hypertension were similar, but the infants with RSV infection had a higher mortality rate (37 per cent vs. 6.5 per cent, P less than 0.1).

A naturally occurring epizootic caused by Sendai virus in breeding and aging rodent colonies. I. Infection in the mouse

An acute Sendai virus epizootic occurred simultaneously in a breeding colony, in experimental and stock animal rooms, and in a colony of aging mice. During the 2-month period that the infection was at its maximum, death rates were approximately doubled. In some strains, the preweanling death rate reached 100%. RFM and BALB/c mice were most susceptible and NZB mice least susceptible. The mortality during the period of Sendai virus infection was increased for most strains and age groups except for the oldest female RFM and NZB mice. Death rates during the epizootic were lowest in young adult mice (greater than 10 weeks of age) and highest in the very young mice (less than 10 weeks of age) and in the oldest male and the moderately aged female mice. Although a substantial number of older mice died during the epizootic, examination of the age-specific death rates indicated that the increase in deaths remained relatively constant for all ages over 10 weeks. This showed that the older mice were not more susceptible to Sendai virus infection. As a sequela of the epizootic, focal chronic pneumonia was found in 10-40% of the mice coming to necropsy even 1 year later.

Respiratory syncytial virus infection in north-east England

During a period covering four winter epidemics 987 respiratory syncytial (RS) virus infections were identified in the children's wards that served a total population of about 875 000 in north-east England. The incidence of admission to hospital with RS virus infection tended to be twice as high among children in Tyneside as that among children from the rest of the catchment area. The risk of hospital admission with RS virus infection in the first year of life for city children was about 1 in 50. The risk tended to be increased when there was a high proportion of children in the population, overcrowded housing, and unemployment. There was no clear relation between climatic changes and the onset or progress of epidemics. Thirteen deaths associated with RS virus infection were identified, four of them sudden and unexpected at home, and nine of them in children with congenital or acquired abnormalities. Twelve children were admitted twice with distinct RS virus infections; the relative severity of their two illnesses depended on age. Hospital cross-infection accounted for 60 of the 987 illnesses. Large families and overcrowding among poorer families seem to lead to a higher incidence of RS virus infection, and measures to reduce overcrowding and improve housing should help to reduce the spread of infection. Breast-feeding also protects infants from infection, but further information is needed to pinpoint the infants at greater risk and how they may best be protected.