Differing manifestations of respiratory syncytial virus-associated severe lower respiratory tract infections in human immunodeficiency virus type 1-infected and uninfected children

Reshaping Our Knowledge: Advancements in Understanding the Immune Response to Human Respiratory Syncytial Virus

Human respiratory syncytial virus (hRSV) is a significant cause of respiratory tract infections, particularly in young children and older adults. In this review, we aimed to comprehensively summarize what is known about the immune response to hRSV infection. We described the innate and adaptive immune components involved, including the recognition of RSV, the inflammatory response, the role of natural killer (NK) cells, antigen presentation, T cell response, and antibody production. Understanding the complex immune response to hRSV infection is crucial for developing effective interventions against this significant respiratory pathogen. Further investigations into the immune memory generated by hRSV infection and the development of strategies to enhance immune responses may hold promise for the prevention and management of hRSV-associated diseases.

During the COVID-19 pandemic where has respiratory syncytial virus gone?

The diffusion of the SARS-CoV-2 virus and the implementation of restrictive measures led to a drastic reduction of respiratory syncytial virus (RSV) diffusion. Few RSV cases have been detected worldwide, even after the removal of the restrictions. We review the current literature and present possible explanations on why there has been a significant reduction of RSV detection during the COVID-19 pandemic. We also hypothesize what may happen when RSV begins to circulate again. The increase of an immunologically naïve population, with infants born from mothers who have not reinforced their immunity to RSV, could lead to greater RSV epidemics in the coming seasons. It is crucial to prepare the scientific community and to keep RSV surveillance active to avoid dramatic consequences.

The impact of cytokine levels in young South African children with and without HIV-associated acute lower respiratory infections

Altered host immune responses are considered to play a key role in the pathogenesis of acute lower respiratory infections (ALRI). The existing literature on cytokine responses in ALRI is largely focussed on adults from developed countries and there are few reports describing the role of cytokines in childhood ALRI, particularly in African or human immunodeficiency virus (HIV)-infected populations. To measure systemic cytokine levels in blood plasma from young South African children with and without ALRI and with and without HIV to determine associations between cytokine responses and disease status and respiratory viral identification. Blood plasma samples were collected from 106 hospitalized ALRI cases and 54 non-ALRI controls less than 2 years of age. HIV status was determined. Blood plasma concentrations of 19 cytokines, 7 chemokines, and 4 growth factors (epidermal growth factor, fibroblast growth factor-basic, hepatocyte growth factor, and vascular endothelial) were measured using The Human Cytokine 30-Plex Panel. Common respiratory viruses were identified by PCR. Mean cytokine concentrations for G-CSF, interferon (IFN)-γ, interleukin (IL)-5, and MCP-1 were significantly higher in ALRI cases than in nonrespiratory controls. Within the ALRI cases, several cytokines were higher in children with a virus compared with children without a virus. Mean cytokine concentrations for IFN-α, IFN-γ, IL-4, IL-5, IL-13, tumour necrosis factor-α, and MIP-1α were significantly lower in HIV-infected cases than in HIV-uninfected cases, while IP-10 and monokine induced by interferon-γ were significantly higher in HIV-infected cases than in HIV-uninfected cases. Certain cytokines are likely to play an important role in the host immune response to ALRI. HIV-infected children have impaired inflammatory responses to respiratory infections compared with HIV-uninfected children.

Pneumococcal Conjugate Vaccine Protection against Coronavirus-Associated Pneumonia Hospitalization in Children Living with and without HIV

SARS-CoV-2 may cause severe hospitalization, but little is known about the role of secondary bacterial infection in these severe cases, beyond the observation of high levels of reported inflammatory markers, associated with bacterial infection, such as procalcitonin. We did a secondary analysis of a double-blind randomized trial of pneumococcal conjugate vaccine (PCV) to examine its impact on human coronavirus (CoV) infections before the pandemic.

In December 2019 a new coronavirus (CoV) emerged as a human pathogen, SARS-CoV-2. There are few data on human coronavirus infections among individuals living with HIV. In this study we probed the role of pneumococcal coinfections with seasonal CoVs among children living with and without HIV hospitalized for pneumonia. We also described the prevalence and clinical manifestations of these infections. A total of 39,836 children who participated in a randomized, double-blind, placebo-controlled clinical trial on the efficacy of a 9-valent pneumococcal conjugate vaccine (PCV9) were followed for lower respiratory tract infection hospitalizations until 2 years of age. Nasopharyngeal aspirates were collected at the time of hospitalization and were screened by PCR for four seasonal CoVs. The frequency of CoV-associated pneumonia was higher in children living with HIV (19.9%) than in those without HIV (7.6%, P < 0.001). Serial CoV infections were detected in children living with HIV. The case fatality risk among children with CoV-associated pneumonia was higher in those living with HIV (30.4%) than without HIV (2.9%, P = 0.001). C-reactive protein and procalcitonin levels were elevated in 36.8% (≥40 mg/liter) and 64.7% (≥0.5 ng/ml), respectively, of the fatal cases living with HIV. Among children without HIV, there was a 64.0% (95% CI: 22.9% to 83.2%) lower incidence of CoV-associated pneumonia hospitalizations among PCV9 recipients compared to placebo recipients. These data suggest that Streptococcus pneumoniae infections might have a role in the development of pneumonia associated with endemic CoVs, that PCV may prevent pediatric CoV-associated hospitalization, and that children living with HIV with CoV infections develop more severe outcomes.

Accuracy of diagnostic tests for respiratory syncytial virus infection within a paediatric hospital population in Kilifi County, Kenya

Background: Respiratory syncytial virus (RSV)-induced lower respiratory tract disease is a prominent cause of hospitalisation among children aged <5 years in developing countries. Accurate and rapid diagnostic tests are central to informing effective patient management and surveillance efforts geared towards quantifying RSV disease burden. This study sought to estimate the sensitivity (Se), specificity (Sp) (along with the associated factors) and predictive values of a direct immunofluorescence test (IFAT), and two real-time reverse transcription polymerase chain reaction (rRT-PCR) assays for RSV infection within a paediatric hospital population: a multiplex rRT-PCR (MPX) and Fast-Track Diagnostics ® (FTD) Respiratory Pathogens 33 (Resp-33) rRT-PCR. Methods: The study enlisted 1458 paediatrics aged ≤59 months admitted with acute respiratory illness at the Kilifi County Hospital between August 2011 and December 2013. A Bayesian latent class modelling framework was employed to infer the tests' estimates based on the patients' diagnostic data from the three tests. Results: The tests posted statistically similar Se estimates: IFAT (93.7%, [90.7; 95.0]), FTD (97.8%, [94.6; 99.4]) and MPX (97.5%, [94.2; 99.3]). As for Sp, FTD registered a lower estimate (97.4%, [96.2; 98.2]) than MPX (99.7%, [99.0; 100.0]) but similar to IFAT (99.0%, [98.2; 99.6]). The negative and positive predictive values were strong (>91%) and closely mimicked the pattern given by the Se and Sp values respectively. None of the examined covariates (age, sex and pneumonia status) significantly influenced the accuracy of the tests. Conclusions: The evaluation found little to choose between the three diagnostic tests. Nonetheless, with its relative affordability, the conventional IFAT continues to hold promise for use in patient care and surveillance activities for RSV infection within settings where children are hospitalised with severe acute respiratory illness.

Case fatality rate and viral aetiologies of acute respiratory tract infections in HIV positive and negative people in Africa: The VARIAFRICA-HIV systematic review and meta-analysis

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This first meta-analysis compare CFR between HIV(+) and HIV(-) with ARTI in Africa

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We found higher rate of mortality in HIV(+) people compared to HIV(-)

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In subgroup analysis, the CFR was higher in HIV + children <5 compared to people >5

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Viral aetiologies of ARTI were not different between HIV(+) and HIV(-)

Background

To set priorities for efficient control of acute respiratory tract infection (ARTI) in Africa, it is necessary to have accurate estimate of its burden, especially among HIV-infected populations.

Objectives

To compare case fatality rate (CFR) and viral aetiologies of ARTI between HIV-positive and HIV-negative populations in Africa.

Study design

We searched PubMed, EMBASE, Web of Knowledge, Africa Journal Online, and Global Index Medicus to identify studies published from January 2000 to April 2018. Random-effect meta-analysis method was used to assess association (pooled weighted odds ratios (OR) with 95% confidence interval (CI)).

Results

A total of 36 studies (126,526 participants) were included. CFR was significantly higher in patients with HIV than in HIV-negative controls (OR 4.10, 95%CI: 2.63–6.27, I²: 93.7%). The risk was significantly higher among children ≤5 years (OR 5.51, 95%CI 2.83–10.74) compared to people aged >5 years (OR 1.48, 95%CI 1.17–1.89); p = 0.0002. There was no difference between children (15 years) and adults and between regions of Africa. There was no difference for viral respiratory aetiologies (Enterovirus, Adenovirus, Bocavirus, Coronavirus, Metapneumovirus, Parainfluenza, Influenza, and Respiratory Syncytial Virus) of ARTI between HIV-positive and HIV-negative people, except for Rhinovirus where being HIV-negative was associated with Rhinovirus (OR 0.70; 95%CI 0.51–0.97, I²: 63.4%).

Conclusions

This study shows an increased risk of deaths among HIV-infected individuals with ARTI, however with no difference in viral aetiologies compared to HIV-negative individuals in Africa. ARTI deserves more attention from HIV health-care providers for efficient control. Specific strategies are needed for HIV-positive children under 5.

Respiratory Syncytial Virus Vaccine Approaches: a Current Overview

PURPOSE OF REVIEW

Respiratory syncytial virus (RSV) is a global human pathogen responsible for lower respiratory tract infections (LRTI). While RSV infection is innocuous in healthy adults, it is the leading cause of infant hospitalization for respiratory tract infection. Nearly everyone shows evidence of an RSV infection by the age of 3. However, there is still not a vaccine commercially available. This review will provide an update on the clinical and preclinical vaccine studies and different approaches to prevent RSV infection.

RECENT FINDINGS

Novel vaccine approaches that induce protection against RSV without enhancement of respiratory tract disease.

SUMMARY

Recent technological approaches have led to generation of different strategies to prevent RSV infection, including live attenuated, chimeric, and subunit vaccines, virus-like particles, and nanoparticles. These vaccine approaches represent promising candidates towards an efficient RSV vaccine that effectively protects infants, children, and adults.

Respiratory viruses in young South African children with acute lower respiratory infections and interactions with HIV

BACKGROUND

Human rhinovirus (RV) is the most common respiratory virus and has been associated with frequent and severe acute lower respiratory infections (ALRI). The prevalence of RV species among HIV-infected children in South Africa is unknown.

OBJECTIVES

To describe the prevalence of respiratory viruses, including RV species, associated with HIV status and other clinical symptoms in children less than two years of age with and without ALRI in Pretoria, South Africa.

STUDY DESIGN

Nasopharyngeal aspirates were collected from 105 hospitalized ALRI cases and 53 non-ALRI controls less than two years of age. HIV status was determined. Common respiratory viruses were identified by PCR, and RV species and genotypes were identified by semi-nested PCR, sequencing and phylogenetic tree analyses.

RESULTS

Respiratory viruses were more common among ALRI cases than controls (83.8% vs. 69.2%; p=0.041). RV was the most commonly identified virus in cases with pneumonia (45.6%) or bronchiolitis (52.1%), regardless of HIV status, as well as in controls (39.6%). RV-A was identified in 26.7% of cases and 15.1% of controls while RV-C was identified in 21.0% of cases and 18.9% of controls. HIV-infected children were more likely to be diagnosed with pneumonia than bronchiolitis (p<0.01). RSV was not identified in any HIV-infected cases (n=15) compared with 30.6% of HIV-uninfected cases (n=85, p=0.013), and was identified more frequently in bronchiolitis than in pneumonia cases (43.8% vs. 12.3%; p<0.01).

CONCLUSIONS

RV-A and RV-C are endemic in South African children and HIV infection may be protective against RSV and bronchiolitis.

Successive Respiratory Syncytial Virus Epidemics in Local Populations Arise from Multiple Variant Introductions, Providing Insights into Virus Persistence

Respiratory syncytial virus (RSV) is a global respiratory pathogen of humans, with infection occurring characteristically as recurrent seasonal epidemics. Unlike influenza viruses, little attention has been paid to the mechanism underlying worldwide spread and persistence of RSV and how this may be discerned through an improved understanding of the introduction and persistence of RSV in local communities. We analyzed 651 attachment (G) glycoprotein nucleotide sequences of RSV B collected over 11 epidemics (2002 to 2012) in Kilifi, Kenya, and contemporaneous data collected elsewhere in Kenya and 18 other countries worldwide (2002 to 2012). Based on phylogeny, genetic distance and clustering patterns, we set out pragmatic criteria to classify local viruses into distinct genotypes and variants, identifying those newly introduced and those locally persisting. Three genotypes were identified in the Kilifi data set: BA (n = 500), SAB1 (n = 148), and SAB4 (n = 3). Recurrent RSV epidemics in the local population were composed of numerous genetic variants, most of which have been newly introduced rather than persisting in the location from season to season. Global comparison revealed that (i) most Kilifi variants do not cluster closely with strains from outside Kenya, (ii) some Kilifi variants were closely related to those observed outside Kenya (mostly Western Europe), and (iii) many variants were circulating elsewhere but were never detected in Kilifi. These results are consistent with the hypothesis that year-to-year presence of RSV at the local level (i.e., Kilifi) is achieved primarily, but not exclusively, through introductions from a pool of variants that are geographically restricted (i.e., to Kenya or to the region) rather than global.

IMPORTANCE The mechanism by which RSV persists and reinvades local populations is poorly understood. We investigated this by studying the temporal patterns of RSV variants in a rural setting in tropical Africa and comparing these variants with contemporaneous variants circulating in other countries. We found that periodic seasonal RSV transmission at the local level appears to require regular new introductions of variants. However, importantly, the evidence suggests that the source of new variants is mostly geographically restricted, and we hypothesize that year-to-year RSV persistence is at the country level rather than the global level. This has implications for control.

The chest X-ray features of chronic respiratory disease in HIV-infected children--a review

Several features of human immunodeficiency virus (HIV) infection contribute to the development of chronic respiratory disease in children. These include the frequency and severity of acute chest infections, as well as the increased risk of pulmonary tuberculosis, aspiration, cardiovascular disease, lymphocytic interstitial pneumonitis or pulmonary neoplasia. The chest radiograph (CXR) remains the most accessible investigation for respiratory disease and plays an important role in the baseline assessment and follow-up. This review focuses on the CXR abnormalities of HIV-related chronic respiratory disease in children. The most commonly documented chronic CXR abnormalities are homogeneous opacification and pulmonary nodules, with pulmonary tuberculosis and lymphocytic interstitial pneumonitis the leading respective causes. Deficiencies in radiographic reporting methodology and relative paucity of radiographic data contribute to current limitations in knowledge and understanding of this field. The review highlights the need for standardised terminology and systematic reporting methodology in future studies. Prospective research on the natural history of lymphocytic interstitial pneumonitis, response to anti-tuberculous therapy, the impact of anti-retroviral therapy and HIV-associated bronchiectasis are needed.

Risks and prevention of severe RS virus infection among children with immunodeficiency and Down's syndrome

By the age of two years, almost all infants are infected with the Respiratory syncytial virus (RSV). One of the main causes of hospitalizations for bronchiolitis and pneumonia at this age is RSV infection. In addition to well-known risks for severe RSV disease, such as prematurity, bronchopulmonary dysplasia and congenital heart disease, immunodeficiencies, chromosomal abnormalities such as Down's syndrome or neuromuscular diseases have also been identified as risks. While the medical needs for RSV prevention in these risk groups are high, clinical evidence to support this is limited. Palivizumab was recently approved in Japan for prophylaxis in children with immunodeficiency or Down's syndrome. A clinical guidance protocol for the prevention of RSV infection using Palivizumab in these risk groups is provided here on the basis of a review of the available literature and on expert opinion. Thus, the present article reviews the published literature related to RSV infections in infants and children with immunodeficiencies or Down's syndrome in order to outline the risks, pathology and physiology of severe RSV disease in these patient groups. The purpose of this article is to facilitate understanding of the medical scientific bases for the clinical guidance.

Clinical epidemiology of bocavirus, rhinovirus, two polyomaviruses and four coronaviruses in HIV-infected and HIV-uninfected South African children

Background

Advances in molecular diagnostics have implicated newly-discovered respiratory viruses in the pathogenesis of pneumonia. We aimed to determine the prevalence and clinical characteristics of human bocavirus (hBoV), human rhinovirus (hRV), polyomavirus-WU (WUPyV) and –KI (KIPyV) and human coronaviruses (CoV)-OC43, -NL63, -HKU1 and -229E among children hospitalized with lower respiratory tract infections (LRTI).

Methods

Multiplex real-time reverse-transcriptase polymerase chain reaction was undertaken on archived nasopharyngeal aspirates from HIV-infected and –uninfected children (<2 years age) hospitalized for LRTI, who had been previously investigated for respiratory syncytial virus, human metapneumovirus, parainfluenza I–III, adenovirus and influenza A/B.

Results

At least one of these viruses were identified in 274 (53.0%) of 517 and in 509 (54.0%) of 943 LRTI-episodes in HIV-infected and -uninfected children, respectively. Human rhinovirus was the most prevalent in HIV-infected (31.7%) and –uninfected children (32.0%), followed by CoV-OC43 (12.2%) and hBoV (9.5%) in HIV-infected; and by hBoV (13.3%) and WUPyV (11.9%) in HIV-uninfected children. Polyomavirus-KI (8.9% vs. 4.8%; p = 0.002) and CoV-OC43 (12.2% vs. 3.6%; p<0.001) were more prevalent in HIV-infected than –uninfected children. Combined with previously-tested viruses, respiratory viruses were identified in 60.9% of HIV-infected and 78.3% of HIV-uninfected children. The newly tested viruses were detected at high frequency in association with other respiratory viruses, including previously-investigated viruses (22.8% in HIV-infected and 28.5% in HIV–uninfected children).

Conclusions

We established that combined with previously-investigated viruses, at least one respiratory virus was identified in the majority of HIV-infected and HIV-uninfected children hospitalized for LRTI. The high frequency of viral co-infections illustrates the complexities in attributing causality to specific viruses in the aetiology of LRTI and may indicate a synergetic role of viral co-infections in the pathogenesis of childhood LRTI.

An investigation into the prevalence and outcome of patients admitted to a pediatric intensive care unit with viral respiratory tract infections in Cape Town, South Africa

OBJECTIVES

To describe the prevalence and outcome of patients admitted to a pediatric intensive care unit with viral respiratory tract infections.

DESIGN

Retrospective descriptive study.

SETTING

Pediatric intensive care unit in a tertiary pediatric hospital situated in Cape Town, South Africa.

PATIENTS

All children (n = 195; 20% pediatric intensive care unit admissions) with positive respiratory viral isolates between April 1 and December 31, 2009.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Demographic, clinical, laboratory, and outcome data were recorded from medical folders. Complete data were available for 175 patients (median age [interquartile range] 4.7 months [2.3-12.9 months]; 49% male). One hundred four (59.4%) patients had comorbid conditions; 30 (17%) were HIV-infected. Rhinovirus (n = 76 [39%]), respiratory syncytial virus (n = 54 [27.7%]), adenovirus (n = 30 [15.4%]), influenza A (n = 26 [13.3%]), parainfluenza (n = 23 [11.8%]), and human metapneumovirus (n = 12 [6.2%]) were most commonly isolated. Ninety-five infections (51.4%) were isolated >48 hrs after admission. Seasonal patterns were identified for respiratory syncytial virus, human metapneumovirus, and influenza A, whereas others occurred throughout the year. Twenty-five patients (14.3%) had more than one viral isolate. Presumed bacterial coinfection, which occurred in 68 (39%) patients (18 [26.5%] HIV-infected), was associated with significantly longer pediatric intensive care unit and hospital stays but not with mortality. Twenty patients died (11%, standardized mortality ratio 0.64). High Pediatric Index of Mortality scores, HIV exposure and infection, nosocomial infection, and influenza A infection were associated with mortality.

CONCLUSIONS

Viral respiratory tract infection is common in this pediatric intensive care unit associated with significant morbidity and mortality, which may relate to the high burden of comorbidity and HIV.

Contribution of common and recently described respiratory viruses to annual hospitalizations in children in South Africa

The contribution of viruses to lower respiratory tract disease in sub‐Saharan Africa where human immunodeficiency virus may exacerbate respiratory infections is not well defined. No data exist on some of these viruses for Southern Africa. Comprehensive molecular screening may define the role of these viruses as single and co‐infections in a population with a high HIV‐AIDS burden. To address this, children less than 5 years of age with respiratory infections from 3 public sector hospitals, Pretoria South Africa were screened for 14 respiratory viruses, by PCR over 2 years. Healthy control children from the same region were included. Rhinovirus was identified in 33% of patients, RSV (30.1%), PIV‐3 (7.8%), hBoV (6.1%), adenovirus (5.7%), hMPV (4.8%), influenza A (3.4%), coronavirus NL63 (2.1%), and OC43 (1.8%). PIV‐1, PIV‐2, CoV‐229E, ‐HKU1, and influenza B occurred in <1.5% of patients. Most cases with adenovirus, influenza A, hMPV, hBoV, coronaviruses, and WU virus occurred as co‐infections while RSV, PIV‐3, and rhinovirus were identified most frequently as the only respiratory pathogen. Rhinovirus but not RSV or PIV‐3 was also frequently identified in healthy controls. A higher HIV sero‐prevalence was noticed in patients with co‐infections although co‐infections were not associated with more severe disease. RSV, hPMV, PIV‐3, and influenza viruses had defined seasons while rhinovirus, adenovirus, and coronavirus infections occurred year round in this temporal region of sub‐Saharan Africa. J. Med. Virol. 83:1458–1468, 2011. © 2011 Wiley‐Liss, Inc.

Identification of deletion mutant respiratory syncytial virus strains lacking most of the G protein in immunocompromised children with pneumonia in South Africa

Respiratory syncytial virus (RSV) G protein deletion mutants replicate effectively in vitro but have not been detected in nature. Subtyping of RSV strains in hospitalized children in South Africa identified G protein PCR amplicons significantly reduced in size in 2 out of 209 clinical specimens screened over 4 years. Sequence analysis revealed subtype B strains lacking nearly the entire G protein ectodomain in one HIV-positive and one HIV-exposed child hospitalized with pneumonia. The association of clinical strains lacking most of the G protein with lower respiratory tract infection in immunocompromised children may have implications for RSV vaccine development.

Epidemiology and prevention of respiratory syncytial virus infections among infants and young children

Since its discovery in 1956, respiratory syncytial virus (RSV) has been recognized as one of the most common causes of serious lower respiratory tract infections in young children worldwide. While considered a high priority, development of a safe and effective vaccine has remained elusive. Prevention of RSV disease relies on infection control and hygiene measures, as well as providing immunoprophylaxis in select infants. The prophylaxis, however, is costly, and so targeting the recipient population and timing of administration is important for optimal effectiveness and judicious use of limited health care resources. This article reviews the epidemiology of RSV infections in infants and young children, including risk factors for severe disease, so as to inform decisions about prevention efforts.

Special populations: do we need evidence from randomized controlled trials to support the need for respiratory syncytial virus prophylaxis?

Congenital abnormalities and impaired mechanisms that govern the normal coordinated physiology of breathing, sucking, swallowing and airway clearance, place infants with underlying medical disorders at high risk for respiratory morbidity following respiratory syncytial virus (RSV) lower respiratory tract infection. The use of RSV prophylaxis in premature infants' ≤ 35 weeks gestational age, infants with chronic lung and hemodynamically significant heart disease is firmly established through randomized controlled clinical trials (RCT's). RSV prophylaxis in infants with serious medical illnesses must be justified based on emerging scientific literature and the overriding concept of achieving a balance between benefit and harm with treatment. This article will explore the current evidence for palivizumab prophylaxis in a variety of disorders and examine existing differences between pediatric advisory body recommendations and real world practice.

Severe respiratory syncytial virus (RSV) infection in infants with neuromuscular diseases and immune deficiency syndromes

Respiratory syncytial virus (RSV) is an important cause of lower respiratory tract infection (LRTI) in infants and children. There is growing evidence of severe RSV disease in infants with neuromuscular diseases and immune deficiency syndromes. Factors predisposing to a more severe course of RSV disease in neuromuscular diseases include the impaired ability to clear secretions from the airways due to ineffective cough, respiratory muscle weakness, high prevalence of gastro-oesophageal reflux and swallowing dysfunction which leads to aspiration. Similarly, pulmonary disease is a common presenting feature and complication of T-cell immunodeficiency. Infants with severe congenital and acquired immune deficiency syndromes may demonstrate prolonged viral shedding in RSV LRTI and are reported to have increased morbidity and mortality associated with RSV infection. Although not indicated in most guideline statements, palivizumab prophylaxis for these uncommon underlying conditions is under consideration by clinicians. Prospective studies are needed to determine the burden of RSV disease in these children.

Factors associated with increased risk of progression to respiratory syncytial virus-associated pneumonia in young Kenyan children

Objectives

To identify factors associated with developing severe respiratory syncytial virus (RSV) pneumonia and their commonality with all-cause lower respiratory tract infection (LRTI), in order to isolate those risk factors specifically associated with RSV-LRTI and identify targets for control.

Methods

A birth cohort of rural Kenyan children was intensively monitored for acute respiratory infection (ARI) over three RSV epidemics. RSV was diagnosed by immunofluorescence of nasal washings collected at each ARI episode. Cox regression was used to determine the relative risk of disease for a range of co-factors.

Results

A total of 469 children provided 937 years of follow-up, and experienced 857 all-cause LRTI, 362 RSV-ARI and 92 RSV-LRTI episodes. Factors associated with RSV-LRTI, but not RSV-ARI, were severe stunting (z-score ≤−2, RR 1.7 95%CI 1.1–2.8), crowding (increased number of children, RR 2.6, 1.0–6.5) and number of siblings under 6 years (RR 2.0, 1.2–3.4). Moderate and severe stunting (z-score ≤−1), crowding and a sibling aged over 5 years sleeping in the same room as the index child were associated with increased risk of all-cause LRTI, whereas higher educational level of the primary caretaker was associated with protection.

Conclusion

We identify factors related to host nutritional status (stunting) and contact intensity (crowding, siblings) which are distinguishable in their association with RSV severe disease in infant and young child. These factors are broadly in common with those associated with all-cause LRTI. The results support targeted strategies for prevention.

Molecular epidemiological analysis of a nosocomial outbreak of respiratory syncytial virus associated pneumonia in a kangaroo mother care unit in South Africa

Respiratory syncytial virus (RSV) may cause severe lower respiratory tract disease in premature infants. Prolonged viral shedding has been reported in patients with underlying immunosuppressive disorders, such as human immunodeficiency virus 1 (HIV-1) infection. During March to May 2006, 23 preterm pediatric patients developed nosocomial pneumonia in a district hospital in the Gauteng Province of South Africa due to RSV infection. The patients were identified using routine diagnostic testing. All had been admitted with their mothers to a Kangaroo Mother Care (KMC) ward from birth--a low care unit for the management of stable low birth weight infants. The HIV-1 seroprevalence among the mothers to these infants was 52.6%, translating to a 52.6% perinatal exposure. A multiplex nested RT-PCR was used to subtype RSV positive nasopharyngeal aspirates. Sequencing and phylogenetic analysis of part of the G-protein gene was used for molecular epidemiological analysis of the outbreak. In total, 19 of the 23 RSV positive specimens could be PCR amplified and sequenced. The subtype A, GA5 genotype was identified in 14 specimens and the BA genotype, a new subtype B genotype not previously recognized in South Africa, in seven. One patient had an infection with both genotypes. Phylogenetic analysis demonstrated eight separate introductions. Two of the strains identified in this outbreak were identical to strains circulating in a general pediatric ward of this hospital during the preceding month. Inadequate infection control measures by health care providers and mothers to children in KMC units may increase potentially the risk of severe RSV infection in a population group with compounded risk factors.

Respiratory viruses other than influenza virus: impact and therapeutic advances

Though several antivirals have been developed and marketed to treat influenza virus infections, the development of antiviral agents with clinical activity against other respiratory viruses has been more problematic. Here we review the epidemiology of respiratory viral infections in immunocompetent and immunocompromised hosts, examine the evidence surrounding the currently available antivirals for respiratory viral infections other than influenza, highlight those that are in the pipeline, and discuss the hurdles for development of such agents.

Seasonality, incidence, and repeat human metapneumovirus lower respiratory tract infections in an area with a high prevalence of human immunodeficiency virus type-1 infection

BACKGROUND

There is limited information regarding the epidemiology of human metapneumovirus (hMPV) from Africa, despite it being identified as a common pathogen in children with pneumonia.

OBJECTIVES

Determine the epidemiology of severe hMPV-associated lower respiratory tract infection (LRTI) in human immunodeficiency virus type-1 (HIV) infected and uninfected children.

METHODS

Nasopharyngeal aspirate samples from children hospitalized for LRTI between January 2000 and December 2002 were analyzed for common respiratory viruses using an immunofluorescence assay; and 2715 available nasopharyngeal aspirate samples were tested for hMPV by reverse-transcriptase polymerase chain reaction targeting its fusion protein. Phylogenetic analysis of the fusion (F) gene was performed on samples associated with repeat hMPV infections in the same child.

RESULTS

hMPV was identified perennially and was the second most commonly identified respiratory virus (11.3% versus 21.1% for respiratory syncytial virus, P < 0.0001) in HIV-uninfected children. The burden of hospitalization for hMPV-LRTI was 5.4 (95% CI: 3.5-7.5) fold greater in HIV-infected (2935 per 100,000) compared with HIV-uninfected children [575 (95% CI: 472-695) per 100,000]. HIV-infected children had greater evidence of bacterial coinfection and a higher mortality rate than did uninfected children. Repeat hMPV associated hospitalizations involved homologous (B2 subgroup) and heterologous (A1 and B2) hMPV.

CONCLUSIONS

There is a high burden of hMPV-LRTI and repeat severe infections occur from homologous and heterologous subgroups of the virus.

Five-year cohort study of hospitalization for respiratory syncytial virus associated lower respiratory tract infection in African children

OBJECTIVES

To describe the epidemiology of respiratory syncytial virus (RSV) associated lower respiratory tract infection (RSV-LRTI) hospitalizations in South African children over a 5-year period, and determine the impact of gestational age (GA) on the incidence of RSV-LRTI hospitalization.

STUDY DESIGN

A cohort of 39,836 children, 6.47% of whom were HIV infected, enrolled into a phase 3 trial were prospectively studied for respiratory viruses when hospitalized for LRTI.

RESULTS

The incidence of hospitalization for RSV-LRTI was 19.4 per 1000 in HIV uninfected children and 2.5-fold (95% CI 2.04-3.03) greater in HIV infected children (45.0 per 1000). The incidence of RSV-LRTI was 4.9-fold greater (95% CI 3.9-6.8) in children born at <36 weeks of gestational age (GA) and repeat hospitalizations for RSV-LRTI was 3.7-fold (95% CI 1.4-9.4) more likely in these children (7.3%) than children born at > or =36 weeks of GA (1.9%). The burden of RSV-LRTI was greater in children born at <32 weeks of GA than those born at 32-35 weeks of GA between 6-12 months (P=0.008) and 12-24 months of age (P=0.001). The RSV epidemic occurred at the end of the rainy season and peaked when the monthly temperatures were at its lowest each year.

Respiratory virus infections in children with cancer or HIV infection

Most studies focusing on respiratory infections in immunocompromised children have been addressed to bacterial etiology. However, respiratory virus infections in this population can also lead to severe disease. The objective of this study is to evaluate the clinical significance of respiratory virus infections in children with cancer or human immunodeficiency virus (HIV) infection. Retrospective study conducted in a teaching hospital in Madrid. Medical records from children <or=14 years diagnosed with cancer or with HIV infection were reviewed. We analyzed demographic characteristics, clinical syndromes associated with the infection, need for hospitalization, treatment prescribed, and outcome. Fifty-three respiratory viral infections were identified: 26 (20%) in 129 HIV-infected children and 27 (12%) in 218 children with cancer. Twenty (38%) of the respiratory infections were nosocomial. Causal viruses were: respiratory syncytial virus, 43%; influenza A, 26%; adenovirus, 13%; parainfluenza virus, 13%; and influenza B, 4%. Thirty-three children were hospitalized: 14 (54%) with HIV infection and 19 (70%) receiving anticancer chemotherapy. Pneumonia occurred in 11 (34%) of the 33 hospitalized children. Four (21%) of the 19 hospitalized children with cancer, but none of the HIV-infected children, were admitted to the Pediatric Intensive Care Unit (P=0.096). Two children with cancer died. Common respiratory virus infections in children with cancer or HIV infection have a relevant morbidity. The fact that 40% of these infections are hospital-acquired emphasizes the need for isolation and preventive measures.

Sepsis predisposition in children with human immunodeficiency virus

OBJECTIVE

To review predisposition to sepsis in children infected with human immunodeficiency virus (HIV) in the era of highly active antiretroviral therapy (HAART).

DESIGN

Summary of the literature with review by experts in the field.

RESULTS

In industrialized regions, new diagnoses of vertically acquired HIV infection are falling due to perinatal interventions. Provision of HAART has resulted in an enlarging cohort of clinically stable HIV-infected children, with low viral loads and normal CD4 T-lymphocyte counts. Access to HAART in "developed" countries has markedly decreased the rate of progression to acquired immunodeficiency syndrome, the prevalence of organ-specific complications of HIV, the risk of recurrent sepsis, and the high early childhood mortality from HIV infection. There are currently no data on whether initiation of HAART during acute sepsis reduces short-term morbidity or mortality. Undiagnosed, antiretroviral-naive, HIV-infected infants still present sporadically with opportunistic infections such as Pneumocystis jiroveci and cytomegalovirus pneumonia. HIV-infected children have a greater burden of disease due to viral, bacterial, and fungal sepsis, and the case fatality rate for nonopportunistic infections may be greater than in non-HIV-infected children. In "developing" countries, with limited access to HAART, the natural history of HIV infection has altered very little, with the majority of infected children dying from either opportunistic or nonopportunistic disease before 3 yrs of age.

CONCLUSION

Pediatric HIV infection is not a homogeneous condition in the era of HAART. Susceptibility to sepsis, morbidity, and mortality differ according to stage of disease, access to HAART, and virologic and immunologic response to treatment. These issues should be considered if HIV-infected children are to be enrolled and stratified in clinical trials.

Importance of nosocomial respiratory syncytial virus infections in an African setting

OBJECTIVE

To define the importance of nosocomial-acquired respiratory syncytial virus (RSV) infection in an area with a high prevalence of paediatric HIV-1 infection.

METHODS

A prospective study was performed that involved all children hospitalized to a general paediatric ward during the course of an RSV epidemic. These children were screened within 24 h of admission and subsequently at 3-4 day intervals for RSV infection using a direct immunofluorescence assay.

RESULTS

RSV was detected in 36 (11.8%) of the 305 children upon initial investigation. Fourteen (38.9%) of the 36 children with community-acquired RSV infection were HIV-1 infected. Repeat sampling for RSV infection was performed in 130 children who tested negative for RSV infection on initial screening and who were hospitalized for > or =3 days. Nosocomial acquisition of RSV occurred among 11.5% of these children, of whom 33% were HIV-1 infected. Fourteen (93.3%) of the children with nosocomial RSV acquisition were clinically symptomatic and treated for 'nosocomial-sepsis'. Furthermore, RSV was isolated from 54% of all children who were investigated for clinically diagnosed nosocomial sepsis. Two (13%) of 15 children with nosocomial RSV infection died; both had other underlying medical conditions.

CONCLUSION

RSV is an important under-recognized cause of nosocomial infection and sepsis among children in this African country. Active interventions are warranted in addressing this problem, as has been successfully undertaken in developed countries.

Human metapneumovirus-associated lower respiratory tract infections among hospitalized human immunodeficiency virus type 1 (HIV-1)-infected and HIV-1-uninfected African infants

Respiratory tract infections due to human metapneumovirus (hMPV) have been reported worldwide, with the exception of Africa. The prevalence of hMPV infection was studied among human immunodeficiency virus type 1 (HIV-1)-infected and HIV-1-uninfected African infants who were hospitalized for lower respiratory tract infections (LRTIs). Nasopharyngeal aspirate samples obtained from 81 HIV-1-infected and 110 HIV-1-uninfected infants who had tested negative for other respiratory viruses were selected for investigation. hMPV was detected in 10 HIV-1-uninfected infants (9.1%) and 3 HIV-1-infected infants (3.7%). Compared with the entire cohort of HIV-1-uninfected infants, hMPV was 4.6-fold less common than respiratory syncytial virus, but it was 3.2-fold more common than influenza virus and 2.1-fold more common than parainfluenza virus types 1-3. Genotyping of 7 of 14 isolates revealed the circulation of 2 major phylogenetic groups of the virus, which were similar to those described in North America and Europe.

Respiratory syncytial virus associated illness in high-risk children and national characterisation of the circulating virus genotype in South Africa

BACKGROUND

There is limited information about respiratory syncytial virus (RSV) in high-risk children from developing countries or on the genotype characterisation of the circulating virus.

OBJECTIVE

To define the proportion of children with RSV associated lower respiratory tract infections (LRTI) that had risk factors for severe disease and to genotype the circulating RSV strains across the country.

STUDY DESIGN

A prospective study was performed in four distinct regions. During April 2000-December 2000 (period 1), all children, with LRTI or without underlying high risk factors for severe RSV disease were enrolled. During January to September 2001 (period 2), only children with LRTI with underlying high risk factors were enrolled. Nasopharyngeal aspirates were evaluated for RSV infection using an ELISA test. RSV isolates were also subtyped and genotyped.

RESULTS

Fifty three (24%) of 220 children enrolled during period 1 had risk factors for severe RSV disease; in addition to which a further 38 high-risk children were enrolled during 2001. RSV was isolated from 16 (30%) of 53 and 37 (22%) of 167 high-risk and non-high risk children, respectively, P=0.31. High-risk children were more likely to require intensive unit care (25 vs. 2.7%, P=0.02) and were also more likely to be hospitalised for a longer duration (median 7 vs. 5 days, P=0.06) than non high-risk infants. Overall (periods 1 and 2), RSV was isolated from 34 (37.4%) of the 91 high-risk infants enrolled. Among high-risk children, those from whom RSV was isolated were more likely to require hospitalisation (73.5 vs. 54.4%, P=0.07) and admission to an intensive care unit (14.7 vs. 1.8%, P=0.03) than those from whom RSV was not isolated. Of 40 isolates subtyped during period one, 92.5% were subtype A. Further, 27 (83.3%) of 30 subtype A isolates genotyped during period 1 clustered with GA2.

CONCLUSION

RSV is an important cause of LRTI among high-risk infants in a developing country such as South Africa. For the season in question, the genotype that was dominant in Johannesburg was isolated throughout the country, suggesting that successful genotypes may have the ability to spread nationwide.

Selected populations at increased risk from respiratory syncytial virus infection

Respiratory syncytial virus (RSV) is the principal cause of bronchiolitis and pneumonia in infants and young children worldwide. Deficits in cellular immunity appear to promote severe RSV disease in children with malignancies, those undergoing chemotherapy and bone marrow transplant recipients. Respiratory syncytial virus infection appears to exacerbate pulmonary symptoms of cystic fibrosis. In such patients RSV disease may result in a prolonged hospital course, which is often complicated by the need for mechanical ventilation. Retrospective analyses of hospital admissions for RSV bronchiolitis among Native American and Alaskan Native children younger than 1 year of age have demonstrated rates of 62 per 1000 or higher, compared with the national average of 34 per 1000. Among these ethnic groups, specific host factors as well as environmental factors appear to contribute to these comparatively high rates of hospitalization for RSV infection. Respiratory syncytial virus has the potential to cause disease in all age groups. A 3-year observational study found that individuals who lived in a community setting, or who cared for young children on a consistent basis, experienced acute respiratory infections more commonly than those living independently or whose interaction with children was limited.

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.

Molecular epidemiological analysis of community circulating respiratory syncytial virus in rural South Africa: Comparison of viruses and genotypes responsible for different disease manifestations

Human respiratory syncytial virus (RSV) is a major cause of severe lower respiratory tract infection in children in both the industrialized and developing world. Most molecular epidemiological studies have, until now, focused on isolates from hospitalized infants in industrialized countries. Limited data have been available with regard to community circulating RSV, especially from Africa. The present study compares RSV isolates from infants attending rural community clinics in the Northern province of South Africa, with isolates from hospitalized infants in Soweto, near Johannesburg, South Africa, during the same period. A multiplex nested polymerase chain reaction was developed for analyzing the clinical specimens, a technique that permits subtyping and nucleotide sequence analysis of the second variable region of the G-protein gene. Community- and hospital-based isolates from young children in South Africa, as well as isolates from Mozambique were compared phylogenetically. One subgroup B community isolate was identified that had a G-protein truncated by approximately 35 amino acids, however, the other community isolates were not significantly different from hospital isolates. Evidence was found that the same RSV genotypes and viruses could cause mild upper respiratory tract infections or lower respiratory tract infections or severe RSV in young infants.

Current concepts on active immunization against respiratory syncytial virus for infants and young children

Respiratory syncytial virus (RSV) is the most important causative agent of viral respiratory tract infections in infants and young children. Passive immunization against RSV became available recently, but this does not apply to an effective vaccine as a result of dramatic adverse results of immunization with a RSV candidate vaccine in the 1960s and the lack of full knowledge of the immune response induced by RSV. Nonetheless intensive research during the past two decades has resulted in several interesting candidate vaccines, of which some have gone through testing in humans. These include the subunit vaccines PFP-1, PFP-2, BBG2Na and cold-passaged/temperature-sensitive mutants. The development of candidate vaccines against RSV is discussed. Because of questions, uncertainties and difficulties with the development of effective vaccines against RSV, it will probably be at least another 5 to 10 years before routine immunization against RSV becomes available.

Lower respiratory tract infections associated with influenza A and B viruses in an area with a high prevalence of pediatric human immunodeficiency type 1 infection

BACKGROUND

Despite the high burden of pediatric HIV-1 infection in developing countries, there are few data on the clinical course of influenza virus-associated lower respiratory tract infection (LRTI) in these children.

OBJECTIVE

To define and compare the clinical course of HIV-1-infected and -uninfected African children hospitalized with influenza virus associated severe LRTI.

METHODS

Children with severe LRTI were prospectively recruited between March, 1997, and March, 1999, as part of a broader study evaluating the etiology and outcome of this condition in hospitalized HIV-1-infected and -uninfected children. The results of children in whom influenza A or B virus was identified by immunofluorescent antibody staining after shell vial culture are reported. Viruses isolated were typed by hemagglutination inhibition assays.

RESULTS

Twenty-five (21.6%) of the 116 children hospitalized with severe LRTI in whom influenza A or B virus was identified were HIV-1-infected. HIV-1-infected children were older than uninfected children (mean age +/- SD 17.4 +/- 10.8 months vs. 10.2 +/- 8.9 months; P = 0.002). HIV-1-infected children were more likely to have an underlying medical illness (in addition to HIV-1 infection) predisposing them to more severe LRTI (32.0% vs. 13.2%; P = 0.03). HIV-infected children were also more likely to have indirect evidence of bacterial coinfection, including chest radiographic evidence of confluent alveolar consolidation (78.9% vs. 35.1%, P = 0.006), and were less likely be wheezing (8.0% vs. 31.9%, P = 0.01). However, there was no difference in the clinical outcome of HIV-1-infected and -uninfected children. The duration of hospitalization [median (range) 5 (2 to 33) days vs. 4 (0 to 21) days, P = 0.08] and the mortality rates (8.0% vs. 2.2%, P = 0.20) were similar between HWV-1-infected and -uninfected children.

CONCLUSION

HIV-1-infected children hospitalized with severe LRTI associated with influenza virus have an outcome similar to that of HIV-1-uninfected children even in the absence of antiretroviral or anti-influenza virus treatment.

Genetic diversity and molecular epidemiology of respiratory syncytial virus over four consecutive seasons in South Africa: identification of new subgroup A and B genotypes

The molecular epidemiology of respiratory syncytial virus (RSV) was studied over four consecutive seasons (1997-2000) in a single tertiary hospital in South Africa: 225 isolates were subgrouped by RT-PCR and the resulting products sequenced. Subgroup A predominated in two seasons, while A and B co-circulated approximately equally in the other seasons. The nucleotide sequences of the C-terminal of the G-protein were compared to sequences representative of previously defined RSV genotypes. South African subgroup A and subgroup B isolates clustered into four and five genotypes respectively. One new subgroup A and three new subgroup B genotypes were identified. Different genotypes co-circulated in every season. Different circulation patterns were identified for group A and B isolates. Subgroup A revealed more variability and displacement of genotypes while subgroup B remained more consistent.