Clinical and epidemiologic aspects of respiratory syncytial virus antigenic variants in Argentinian children

Epidemiological changes of respiratory syncytial virus (RSV) infections in Israel

RSV is the leading cause of lower respiratory-tract infections in infants and therefore demands in-depth epidemiological characterization. We investigated here the distribution of RSV types in Israel between the years 2005–2012. Clinical samples were collected from 11,018 patients hospitalized due to respiratory illnesses and were evaluated for the presence of various respiratory viruses, including RSV A and RSV B. Until 2008, each year was characterized by the presence of one dominant type of RSV. However, from 2008, both RSV A and B types were detected at significant levels, particularly among infants aged 0–2 years. Furthermore, significant changes in the RSV A and RSV B subtypes circulating in Israel since 2008 were observed. Finally, we demonstrate that, irrespectively of the changes observed in RSV epidemiology, when the pandemic H1N1pdm09 influenza virus appeared in 2009, RSV infections were delayed and were detected when infection with H1N1pdm09 had declined.

Distribution of respiratory syncytial virus subtypes A and B among infants presenting to the emergency department with lower respiratory tract infection or apnea

BACKGROUND

Respiratory syncytial virus (RSV), a leading viral respiratory pathogen worldwide, has 2 major subtypes, A and B.

OBJECTIVE

To describe the temporal and geographic distribution and parameters of disease severity associated with RSV A and B in the United States.

METHODS

A US multicenter active surveillance study was conducted in emergency departments (EDs) during 2 RSV seasons. Infants <1 year of age presenting to the ED with symptoms of lower respiratory tract infection or apnea were enrolled. RSV subtypes were detected in nasal swabs by reverse transcriptase polymerase chain reaction.

RESULTS

Of 4248 patients enrolled, 4172 patients were evaluable; 32.4% of patients were positive for any RSV subtype in season 1 and 29.9% in season 2. RSV A and B were detected in each region studied. More patients presented to the ED with RSV A than with RSV B (853 [20.4%] versus 453 [10.9%], respectively); RSV A-positive patients were more likely to be admitted to the hospital or intensive care unit (47.7%, versus RSV B, 35.8%; P < 0.0001); hospitalized RSV A-positive patients were less likely to be prescribed antibiotics (32.4%, versus RSV B, 47.8%; P < 0.001).

CONCLUSIONS

This is the largest epidemiologic study in EDs reporting trends in RSV subtypes. RSV subtypes A and B were documented in both seasons across all US regions studied and detected in September to May. The results of this study support suggestions from smaller studies that RSV A may be more virulent than RSV B; however, more quantitative assessments of disease severity are needed.

Molecular epidemiology and disease severity of human respiratory syncytial virus in Vietnam

Respiratory syncytial virus (RSV) is a major cause of acute respiratory infections (ARIs) in children worldwide and can cause high mortality, especially in developing countries. However, information on the clinical and molecular characteristics of RSV infection in developing countries is limited. From April 2010 to May 2011, 1,082 nasopharyngeal swabs were collected from children with ARI admitted to the Children's Hospital 2, Ho Chi Minh City, Vietnam. Samples were screened for RSV and genotyped by reverse transcription-PCR and sequencing. Demographic and clinical data was also recorded. RSV was found in 23.8% (257/1,082) of samples. RSV A was the dominant subgroup, accounting for 91.4% (235/257), followed by RSV B, 5.1% (13/257), and 9 cases (3.5%) were mixed infection of these subgroups. The phylogenetic analysis revealed that all group A strains belonged to the GA2 genotype. All group B strains belonged to the recently identified BA genotype, and further clustered into 2 recently described subgenotypes BA9 and BA10. One GA2 genotype strain had a premature stop codon which shortened the G protein length. RSV infection was significantly associated with younger age and higher severity score than those without. Co-infection with other viruses did not affect disease severity. RSV A caused more severe disease than RSV B. The results from this study will not only contribute to the growing database on the molecular diversity of RSV circulating worldwide but may be also useful in clinical management and vaccine development.

Viral etiology of acute respiratory infections among children in Porto Alegre, RS, Brazil

Although acute respiratory infections (ARIs) are a major cause of child morbidity and mortality in Southern Brazil, little information is available on their seasonality and viral etiology. This study was conducted on children under 5 years of age with ARI to assess viral etiology in the State of Rio Grande do Sul, from 1990 to 1992. A total of 862 nasopharyngeal secretion (NPS) samples were tested using indirect immunofluorescence. The results showed that 316 (36.6%) NPS samples were positive: 26.2% for RSV, 6% for adenovirus, 1.7% for influenza viruses, 1.5% for parainfluenza viruses, and 1.2% for mixed infection. The mean viral prevalence rates in out-patient services, emergency wards, and in-patient hospital wards were 26.7%, 53% and 42.3%, respectively. Respiratory syncytial virus (RSV) and adenovirus accounted for 91.4 % of the viral diagnoses. RSV was more frequent in children under one year of age at the three levels of health care and was prevalent in infants under six months. Adenovirus was the most prevalent pathogen in hospitalized children, in 1992. Influenza A virus showed an increased prevalence with age among out-patient children. This study shows the annual occurrence of viral respiratory infections in the coldest months, with a significant annual variation in the frequency of RSV infection.

Occurrence and severity of infections caused by subgroup A and B respiratory syncytial virus in children in southeast Brazil

The frequency and severity of infections caused by respiratory syncytial virus (RSV) were assessed in children <2 years of age seen at the emergency department. The frequency of RSV detection in the clinical virology laboratory during the past 3 years was also analyzed retrospectively. RSV was found in 21.6% (188/869) of the samples collected from children seen at the emergency department and was found to be more frequent during the autumn, being less frequent or negligible by midwinter. RSV subgroups A and B co-circulated within the same time period in children seen at the emergency department, with varying predominance of either subgroup. There was no significant association of RSV subgroup with disease severity, but only a trend for RSV subgroup B being more frequent in children with risk factors for severe disease.

Molecular epidemiology of respiratory syncytial virus

Human respiratory syncytial virus (RSV) is the major cause of lower respiratory tract disease in infants. It is unusual in that it causes repeated infections throughout life. Despite considerable efforts there is as yet no satisfactory vaccine available. This paper reviews the molecular epidemiology of the RSV and describes the complex genotypic structure of RSV epidemics. The evolution of the virus is discussed, with particular reference to the antigenic and genetic variability of the attachment glycoprotein.

Respiratory syncytial virus groups A and B in Porto Alegre, Brazil, from 1990 to 1995 and 1998

We analyzed the respiratory syncytial virus (RSV) groups and their epidemiological pattern that were detected over the course of seven years in southern Brazil. The two RSV groups co-circulated each year, but frequencies of groups A and B varied both between and within yearly outbreaks. In 1991, group A predominated over group B (p=0.0016). RSV outbreaks analyzed showed a temperature-dependent pattern and no association with rainfall, similarly to other countries from southern South America. Knowledge of the variants is important in terms of both diagnosis and definition of a vaccine composition.

G protein variation in respiratory syncytial virus group A does not correlate with clinical severity

Respiratory syncytial virus group A strain variations of 28 isolates from The Netherlands collected during three consecutive seasons were studied by analyzing G protein sequences. Several lineages circulated repeatedly and simultaneously during the respective seasons. No relationships were found between lineages on the one hand and clinical severity or age on the other.

Respiratory syncytial virus: changes in prevalence of subgroups A and B among Argentinian children, 1990-1996

The frequency of respiratory syncytial virus (RSV) and the distribution of subgroups A and B strains during 7 consecutive years (1990-1996) were examined in two cities of Argentina. Nasopharyngeal aspirates from 1,304 children less than 2 years of age hospitalized with acute lower respiratory infection were studied by indirect immunofluorescence. RSV was detected in 352 cases (26.9%), and the peak activity was observed in midwinter. Subgroup characterization was performed with two monoclonal antibodies against the F protein on nasopharyngeal aspirate smears. Of 195 samples, 174 (89.2%) were identified as subgroup A strains and 21 (10.8%) as subgroup B. Both strains cocirculated during 5 of 7 years studied with subgroup A predominating. Subgroup A occurred at least 8 times as often in all years except for 1994-1995. Children infected by subgroup A were younger than those infected by subgroup B (P < 0.05). The association of subgroup A infection with bronchiolitis and subgroup B with pneumonia was statistically significant (P < 0.03).

Clinical and epidemiologic characteristics of respiratory syncytial virus subgroups A and B infections in Santa Fe, Argentina

Respiratory Syncytial Virus (RSV) has two major antigenic groups, A and B. The implications of these variants in the epidemiology and pathogenesis of RSV infection are not well defined. This study was undertaken to compare the two RSV subgroups in patients admitted to hospital. Clinical and epidemiologic features of RSV subgroups in children under 30 months of age with proven RSV acute lower respiratory infections were examined during 4 winters from 1993 to 1996 in Santa Fe, Argentina. RSV typing was carried out with monoclonal antibodies in nasopharyngeal cells by indirect immunofluorescence. Of the 177 RSV positive nasopharyngeal aspirates obtained from 1993 to 1996, 85 (48%) were available for typing. Seventy-three (85.9%) specimens were identified as Subgroup A and 12 (14.1%) as Subgroup B. Except in 1993, in which only Subgroup A was detected, both variants circulated throughout the epidemic season. Subgroup A infections produced more severe disease than Subgroup B infections, as assessed by the length of the hospital stay and the use of respiratory support. This difference was age related, being evident in infants 0-6 months old. Patients with Subgroup B infections were also significantly less frequently breast-fed (95% vs. 75% for A and B subgroups, respectively; P = 0.04). It is concluded that the severity of disease in Argentinian patients admitted with acute RSV infections may be associated with Subgroup A strains as determined by a serogrouping method.

Incidence of acute otitis media associated with group A and B respiratory syncytial virus infections

The comparative association of respiratory syncytial virus group A and B infections with acute otitis media was determined by analysing the hospital records of children with community-acquired respiratory syncytial virus infection during three successive outbreaks from 1987 to 1992. Of 326 episodes analysed, 192 (59%) were caused by group A and 134 (41%) by group B infections. Acute otitis media was diagnosed in 101 (75%) children with group B infection, compared with 119 (62%) with group A infection (p = 0.01). Group A infections were more often associated with wheezing (71% versus 59% in group B; p = 0.02) and oxygen therapy in inpatients (48% versus 31%, respectively; p = 0.008). The higher incidence of acute otitis media associated with group B infections was observed both after adjustment for potential confounding variables and during each outbreak.

Subgrouping of respiratory syncytial virus strains from Australia and Papua New Guinea by biological and antigenic characteristics

Strains of respiratory syncytial virus from 3 major areas of Australia and Papua New Guinea (PNG) were analyzed for variations in their antigenic and biological properties and in the molecular weights of their major structural proteins. Seventy-eight strains from infants and young children with LRI were collected from 1981-1984. The RSV season in the Australian cities lasted from April through September, with major peaks in July of each year, while the RSV season in tropical PNG was year-round, with small peaks in March and October of each year coinciding with excessive rainfall. Fifty-six strains were analyzed in detail; 40 were typed by time-resolved fluoroimmunoassay with monoclonal antibodies as group A strains and 16 were group B; both groups were concurrent. Three children of one family had sequential RSV infections 13 months apart, and the etiologic group A strain was identical both years in terms of growth and antigenic properties with strain-specific ferret antisera; the second infection was milder in all three children. On average, the group A strains replicated considerably better than group B strains in HEp2 cells, producing 53% more syncytia and 99% higher infectious virus titers in 31% less time in culture. Ten group A and B reference strains exhibited the same growth patterns as the A and B regional strains, respectively. Differences in antigenicity as measured with hyperimmune antisera to prototype Long strain were even greater. Group A strains exhibited a mean 68% greater IFA staining than B strains, a 71% greater EIA reaction, and were neutralized to 69% higher serum titers than B strains. Again, the reference A and B strains included as controls gave patterns identical to those of the regional strains. Finally, the P phosphoprotein had consistently higher molecular weight in A strains (mean 35,900) than B strains (mean 33,100). Small variations in the sizes of the F and G glycoproteins were not sufficient to suggest grouping on this basis.

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

A subgroup analysis of 613 specimens submitted to the British Columbia's Children's Hospital from 1987 to 1992 revealed that subgroups A and B of respiratory syncytial virus (RSV) were both circulating in our community, with some predominance for subgroup A during the period from October 1987 to September 1988 (the 1987-88 season) (64%), 1990-91 (60%), and 1991-92 (62%). During 1989-90 subgroup A represented the majority of isolates (80%). Subgroup B predominated during only one season, 1988-89 (94%). No microheterogeneity within subgroups was apparent as judged by the monoclonal antibody reactivity pattern. More male than female children were affected overall, but no sex-related difference between subgroup infections could be detected (P = 0.28). The majority of patients were less than 1 year of age, and no significant association between age and subgroup was detected after stratifying for year (P = 0.64). This is, to our knowledge, the first comprehensive longitudinal RSV subgroup prevalence study from the Pacific Northwest and from Canada.

Respiratory syncytial virus (RSV) bronchiolitis: comparative study of RSV groups A and B infected children

The grouping characteristics of 29 respiratory syncytial virus (RSV) present in nasopharyngeal cells collected from hospitalized children with bronchiolitis during the 1990 RSV season in Porto Alegre, RS, were analysed. Twenty-two were grouped as belonging to group A and 7 to group B. Cyanosis, oxygen therapy, cough, length of hospitalization and atelectasis were observed to be more frequently found within group B infected children. Other clinical signs and symptoms were similarly found in both groups.