Respiratory syncytial virus subgroup B dominance during one winter season between 1987 and 1992 in Vancouver, Canada

Respiratory viral infections in hospitalised paediatric patients in the tropics

AIM

Respiratory viruses are a huge disease burden globally. An understanding of the seasonal trends and the ability to predict peak periods of respiratory virus disease incidence is useful for clinical care.

METHODS

This is a retrospective analysis of paediatric hospitalizations of laboratory-confirmed viral respiratory tract infections in KK Women's and Children's Hospital, Singapore, from 1 January 2011 to 31 December 2016. Standard direct immunofluorescence was used to detect respiratory syncytial virus (RSV), influenza A and B viruses, parainfluenza 1, 2 and 3 viruses, metapneumovirus and adenovirus.

RESULTS

A total of 97 840 specimens were analysed with a positive detection rate of 23.8%. RSV made up the largest proportion (42% of the total positive results), predominating between May to September. Influenza A had two peaks, June to July and December to January. Type 3 was the most common parainfluenza virus and showed annually recurring peaks. In contrast, parainfluenza 1 and 2, metapneumovirus and adenovirus had a biennial pattern. The test of seasonality detected identifiable seasonality for RSV and parainfluenza 3 virus.

CONCLUSIONS

In conclusion, respiratory viruses have different and overlapping seasonality in tropical Singapore. Respiratory virus testing for patients admitted for acute respiratory infection is useful to target antiviral therapies and appropriate infection control practices.

Predicting the hotspots of age-adjusted mortality rates of lower respiratory infection across the continental United States: Integration of GIS, spatial statistics and machine learning algorithms

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Lower respiratory infections (LRI) are the cause of a significant number of hospitalizations in the US.

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No previous nationwide study examined geographic variations of LRI mortality rates and their association with underlying factors.

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There was a shift in the location of LRI hotspots from west coast to southeast over time.

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Decision tree classifiers could predict LRI mortality hotspots with high accuracies.

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Higher spring temperature and increased precipitation during winter were among the most substantial predictors of presence or absence of LRI hotspots.

Objective

Although lower respiratory infections (LRI) are among the leading causes of mortality in the US, their association with underlying factors and geographic variation have not been adequately examined.

Methods

In this study, explanatory variables (n = 46) including climatic, topographic, socio-economic, and demographic factors were compiled at the county level across the continentalUS.Machine learning algorithms - logistic regression (LR), random forest (RF), gradient boosting decision trees (GBDT), k-nearest neighbors (KNN), and support vector machine (SVM) - were employed to predict the presence/absence of hotspots (P < 0.05) for elevated age-adjusted LRI mortality rates in a geographic information system framework.

Results

Overall, there was a historical shift in hotspots away from the western US into the southeastern parts of the country and they were highly localized in a few counties. The two decision tree methods (RF and GBDT) outperformed the other algorithms (accuracies: 0.92; F1-scores: 0.85 and 0.84; area under the precision-recall curve: 0.84 and 0.83, respectively). Moreover, the results of the RF and GBDT indicated that higher spring minimum temperature, increased winter precipitation, and higher annual median household income were among the most substantial factors in predicting the hotspots.

Conclusions

This study helps raise awareness of public health decision-makers to develop and target LRI prevention programs.

Comparative viral frequency in Mexican children under 5 years of age with and without upper respiratory symptoms

In Mexico, there is a lack of up-to-date published data that show viruses to be the main cause of acute respiratory infection (ARI). The objective of this study was to estimate the comparative viral frequency between children under the age of 5 years with and without ARI (n = 179 in each group) in a suburban community (Nezahualcóyotl City). A nasopharyngeal sample was collected for viral culture and identification was carried out by indirect immunofluorescence (IIF) using mAbs. There were no sex differences between the two groups. Children under 1 year of age with ARI showed a higher frequency (56 %) of viral infections; this was statistically significant (P < 0.05) when compared with the same age group in ARI-free children (17 %). Respiratory syncytial virus (RSV) was the most prevalent type of virus isolated from both groups (38 vs 18 %). A statistically significantly higher number of subjects with ARI (33/179) than without (12/179) were infected with RSV (P < 0.003). Prevalences of four other viruses studied were similar in the two groups. The highest viral incidence of ARI in children was detected in the winter-spring seasonal period.

Respiratory syncytial virus epidemics: the ups and downs of a seasonal virus

Respiratory syncytial virus (RSV) is the most common pathogen causing lower respiratory tract infections in infants worldwide. Lower respiratory tract infections caused by RSV occur epidemically, and the appearance of epidemics seems to vary with latitude, altitude and climate. This study uses a review of the literature on RSV seasonality to investigate whether a global pattern in RSV epidemics can be found. A comparison of morbidity and mortality caused by RSV in developed vs. developing countries is also presented. The seasons in which RSV epidemics occur typically depend on geographic location and altitude. During these seasons the epidemics tend to appear in clusters. Although the appearance pattern of these epidemics varies from one continent to another, they usually begin in coastal areas. RSV is the cause of one-fifth of lower respiratory infections worldwide. Generally RSV mortality is low, with a median value of zero. However, RSV mortality in developing countries is significantly higher than RSV mortality in developed countries.

Seasonal pattern of early mortality and infectious complications in liver transplant recipients

Seasonal variation has been documented in the frequency and attributable mortality of a number of medical illnesses and infections in the nontransplantation setting. Whether similar trends exist in transplant recipients is not known. Seasonal rates of overall and early mortality and contributory variables stratified by season were assessed in 190 consecutive liver transplant recipients who underwent transplantation over a 10-year period. The frequency of infectious complications and rejection was also assessed and stratified by season of transplantation. Early (deaths occurring in the first year posttransplantation), but not overall, mortality correlated significantly with seasonality. Of patients with early mortality, 43% (13 of 30 patients) died in winter; 23% (7 of 30 patients), in spring; 13% (4 of 30 patients), in summer; and 20% (6 of 30 patients), in fall. The frequency of deaths in winter was significantly greater than for all other seasons (P = .022). The high wintertime mortality could not be explained by previously recognized risk factors portending a poor outcome, e.g., United Network for Organ Sharing status, Child-Pugh score, surgical time, blood loss, pretransplantation and posttransplantation dialysis, infections, rejection, or increased immunosuppression. Strong trends toward a higher rate of cytomegalovirus disease in patients who underwent transplantation in fall (P = .09) and bacterial infections in those who underwent transplantation in winter were documented (P = .09). There was no correlation between seasonality and rejection. Early mortality in winter in liver transplant recipients was significantly greater than if the deaths were totally random. Whether the seasonal clustering of deaths and infections is triggered by respiratory viruses, yet unrecognized viruses, or unknown exogenous factors remains to be determined.

Respiratory syncytial virus subgroup A in hospitalized children in Zarqa, Jordan

The epidemiology of RSV infection was investigated in 271 children aged less than 2 years admitted to the Zarqa Government Hospital, Jordan with bronchiolitis or bronchopneumonia. Nasopharyngeal washings were cultured and RSV antigen was detected by the direct immunofluorescence technique. Of the 271 specimens, 69 (25.46%) were positive for RSV, representing 50.36% of the respiratory viruses. All RSV isolates were typed as subgroup A by monoclonal antibody and confirmed by RT-PCR. RSV was prevalent in the hospitalised children in the coldest months of the year. The epidemics began in January or February, peaked in spring and then disappeared in summer. This study supports the idea that RSV subgroup A is a major contributor to winter outbreaks of respiratory tract disease in children, and health care workers in Jordan should consider the diagnosis during January-May each year.

Respiratory syncytial virus genetic and antigenic diversity

Respiratory syncytial virus (RSV) is a major cause of viral lower respiratory tract infections among infants and young children in both developing and developed countries. There are two major antigenic groups of RSV, A and B, and additional antigenic variability occurs within the groups. The most extensive antigenic and genetic diversity is found in the attachment glycoprotein, G. During individual epidemic periods, viruses of both antigenic groups may cocirculate or viruses of one group may predominate. When there are consecutive annual epidemics in which the same group predominates, the dominant viruses are genetically different from year to year. The antigenic differences that occur among these viruses may contribute to the ability of RSV to establish reinfections throughout life. The differences between the two groups have led to vaccine development strategies that should provide protection against both antigenic groups. The ability to discern intergroup and intragroup differences has increased the power of epidemiologic investigations of RSV. Future studies should expand our understanding of the molecular evolution of RSV and continue to contribute to the process of vaccine development.

Respiratory syncytial virus genetic and antigenic diversity

Respiratory syncytial virus (RSV) is a major cause of viral lower respiratory tract infections among infants and young children in both developing and developed countries. There are two major antigenic groups of RSV, A and B, and additional antigenic variability occurs within the groups. The most extensive antigenic and genetic diversity is found in the attachment glycoprotein, G. During individual epidemic periods, viruses of both antigenic groups may cocirculate or viruses of one group may predominate. When there are consecutive annual epidemics in which the same group predominates, the dominant viruses are genetically different from year to year. The antigenic differences that occur among these viruses may contribute to the ability of RSV to establish reinfections throughout life. The differences between the two groups have led to vaccine development strategies that should provide protection against both antigenic groups. The ability to discern intergroup and intragroup differences has increased the power of epidemiologic investigations of RSV. Future studies should expand our understanding of the molecular evolution of RSV and continue to contribute to the process of vaccine development.

The fluctuating pattern of various genome types of respiratory syncytial virus in Copenhagen and some other locations in Denmark

A semi-nested RT-PCR method based on a region of the F and G glycoprotein genes was established, allowing the simultaneous detection and differentiation of group A and group B isolates of respiratory syncytial virus (RSV). The PCR products were subjected to digestion with restriction endonucleases to further differentiate the isolates. Using, in addition, previously reported studies the prevalence of various genome types in the Copenhagen region over a period of 6 years was established. Furthermore, the prevalence of genome types was determined in a distant region in Denmark during the winters of 1996/97 and 1997/98, and in yet another distant region during the winter of 1997/98. It was shown that the different regions in Denmark to a large extent share the same pool of genome types of RSV. Yet, while the fluctuating patterns of the two groups and various genome types were almost identical at different hospitals in the Copenhagen region, they varied between the different regions. This suggests that epidemics in local communities primarily rely on region-specific herd immunity parameters and emerge from strains endemically circulating in these local communities. Group B strains in Copenhagen showed an overall predominance, being predominant in three of the six epidemic seasons studied, and of almost equal predominance in one season.

Severity of respiratory syncytial virus disease related to type and genotype of virus and to cytokine values in nasopharyngeal secretions

BACKGROUND

Investigations concerning the severity of respiratory syncytial virus (RSV) disease as related to (1) RSV type and genotype determined respectively by PCR and restriction enzyme analysis and (2) interleukin 6 (IL-6) and tumor necrosis factor alpha (TNF-alpha) values in samples of nasopharyngeal secretion (NPS) have not been previously reported.

METHODS

We prospectively studied 105 RSV infections in the lower respiratory tract of infants and young children admitted to a pediatric department in Copenhagen during three winter seasons, 1993, 1994 and 1995. RSV strains were typed and genotyped, respectively, by PCR and nucleic acid restriction analysis and correlated to the severity of the disease. The ratio IL-6:TNF-alpha, determined from IL-6- and TNF-alpha values in samples of NPS, was related to the severity of the disease. Concentrations of IL-6 and of TNF-alpha were determined in serum samples taken during 5 weeks after the onset of illness.

RESULTS

Type B infections produced more severe disease than did type A infections, as assessed on the length of the hospital stay, use of respiratory support and the presence of an infiltrate on a chest radiograph. This difference was age-related. It was observed in infants 0 to 5 months old, but not in older age groups. Type B genotype B1122 produced more severe disease than type A genotype A2311 in infants 0 to 11 months old. Increased serum concentrations of IL-6 and TNF-alpha were detected in samples taken 1 to 2 days after the onset of illness. Whereas TNF-alpha serum concentrations remained high, IL-6 serum concentrations decreased during the following 3 to 4 weeks. The IL-6:TNF-alpha ratio in samples of NPS was related to the severity of the disease. A high ratio was related to a low severity.

CONCLUSIONS

The severity of disease in patients admitted with acute RSV infections can be correlated to the RSV type as determined by PCR, to the RSV genotype as determined by nucleic acid restriction analysis and to the ratio IL-6:TNF-alpha in NPS.

Rehospitalization with respiratory syncytial virus after neonatal intensive care unit discharge: A 3-year follow-up

OBJECTIVES

This study sought to determine 1) the incidence of rehospitalization with respiratory syncytial virus (RSV) infection within a 3-year follow-up among infants discharged from the neonatal intensive care unit (NICU), and 2) to examine associations between age at readmission and medical and sociodemographic characteristics among infants rehospitalized with RSV.

METHODS

A 3-year retrospective review of NICU discharges at a tertiary care center identified 2506 infants. Using medical record numbers linked with International Classification of Diseases, 9th ed, diagnostic codes for RSV infection, bronchiolitis, or respiratory distress, 67 NICU graduates were identified as having been readmitted from November to April (RSV season). Bivariate analyses and logistic regression modeling were applied to determine the association between a series of predictor variables and age at readmission with RSV by 90 days, 125 days, and 180 days after discharge from the NICU.

RESULTS

The 3-year incidence of readmission with RSV infection after NICU discharge was 2.7%. During the 3-year follow-up, 6.4% of very low birth weight infants, 2.8% of low birth weight infants, and 1.7% of normal weight infants were readmitted with RSV. Crude results revealed that the presence of bacteremia, intraventricular hemorrhage, and necrotizing enterocolitis, as well as ventilation use, were associated with younger age at readmission with RSV. Simultaneous consideration of the effects of all of these medical predictors and birth weight on age at readmission revealed that normal birth weight was the only significant factor associated with younger age at readmission with RSV.

CONCLUSIONS

This study found significantly lower rates of RSV readmission among NICU graduates than those reported previously in the literature. Based on these data, prophylactic treatment of all preterm infants may not be warranted.

Pediatric Investigators Collaborative Network on Infections in Canada (PICNIC) prospective study of risk factors and outcomes in patients hospitalized with respiratory syncytial viral lower respiratory tract infection

OBJECTIVE

To provide information on disease attributable to respiratory syncytial viral lower respiratory tract infection (RSV LRI) and to quantify the morbidity associated with various risk factors.

DESIGN

Prospective cohort study.

SUBJECTS

Patients hospitalized with RSV LRIs at seven centers were eligible for study if they were younger than 2 years of age, or hospitalized patients of any age if they had underlying cardiac or pulmonary disease or immunosuppression.

MEASUREMENTS AND RESULTS

Enrolled (n = 689) and eligible but not enrolled (n = 191) patients were similar in age, duration of illness and proportion with underlying illness, use of intensive care, and ventilation. Of the enrolled patients, 156 had underlying illness. The isolates from 353 patients were typeable: 102 isolates were subgroup A, 250 were subgroup B, and one isolated grouped with both antisera. The mean hospital stay attributable to respiratory syncytial virus (RSV) was 7 days; 110 patients were admitted to intensive care units, 63 were supported by mechanical ventilation, and 6 patients died. Regression models were developed for the prediction of three outcomes: RSV-associated hospital duration, intensive care unit admission, and ventilation treatment. In addition to previously described risk factors for an increased morbidity, such as underlying illness, hypoxia, prematurity and young age, three other factors were found to be significantly associated with complicated hospitalization: aboriginal race (defined by maternal race), a history of apnea or respiratory arrest during the acute illness before hospitalization, and pulmonary consolidation as shown on the chest radiograph obtained at admission. The RSV subgroup, family income, and day care attendance were not significantly associated with these outcomes.

CONCLUSIONS

Hypoxia on admission, a history of apnea or respiratory arrest, and pulmonary consolidation should be considered in the management of children with RSV LRIs. Vaccine trials should target patients with underlying heart or lung disease or of aboriginal race.

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.