The age profile of respiratory syncytial virus burden in preschool children of low- and middle-income countries: a semi-parametric, meta-regression approach

BACKGROUND: Respiratory syncytial virus (RSV) infections are among the primary causes of death for children under 5 years of age worldwide. A notable challenge with many of the upcoming prophylactic interventions against RSV is their short duration of protection, making the age profile of key interest to the design of prevention strategies. METHODS AND FINDINGS: We leverage the RSV data collected on cases, hospitalizations, and deaths in a systematic review in combination with flexible generalized additive mixed models (GAMMs) to characterize the age burden of RSV incidence, hospitalization, and hospital-based case fatality rate (hCFR). Due to the flexible nature of GAMMs, we estimate the peak, median, and mean incidence of infection to inform discussions on the ideal "window of protection" of prophylactic interventions. In a secondary analysis, we reestimate the burden of RSV in all low- and middle-income countries. The peak age of community-based incidence is 4.8 months, and the mean and median age of infection is 18.9 and 14.7 months, respectively. Estimating the age profile using the incidence coming from hospital-based studies yields a slightly younger age profile, in which the peak age of infection is 2.6 months and the mean and median age of infection are 15.8 and 11.6 months, respectively. More severe outcomes, such as hospitalization and in-hospital death have a younger age profile. Children under 6 months of age constitute 10% of the population under 5 years of age but bear 20% to 29% of cases, 28% to 39% of hospitalizations, and 38% to 50% of deaths. On an average year, we estimate 28.23 to 31.34 million cases of RSV, between 2.95 to 3.35 million hospitalizations, and 16,835 to 19,909 in-hospital deaths in low, lower- and upper middle-income countries. In addition, we estimate 17,254 to 23,875 deaths in the community, for a total of 34,114 to 46,485 deaths. Globally, evidence shows that community-based incidence may differ by World Bank Income Group, but not hospital-based incidence, probability of hospitalization, or the probability of in-hospital death (p ≤ 0.01, p = 1, p = 0.86, 0.63, respectively). Our study is limited mainly due to the sparsity of the data, especially for low-income countries (LICs). The lack of information for some populations makes detecting heterogeneity between income groups difficult, and differences in access to care may impact the reported burden. CONCLUSIONS: We have demonstrated an approach to synthesize information on RSV outcomes in a statistically principled manner, and we estimate that the age profile of RSV burden depends on whether information on incidence is collected in hospitals or in the community. Our results suggest that the ideal prophylactic strategy may require multiple products to avert the risk among preschool children

Immunological and Inflammatory Biomarkers of Susceptibility and Severity in Adult Respiratory Syncytial Virus Infections.

BACKGROUND: . Respiratory syncytial virus (RSV) is the most common cause of bronchiolitis in young infants. However, it is also a significant pathogen in older adults. Validated biomarkers of RSV disease severity would benefit diagnostics, treatment decisions, and prophylactic interventions. This review summarizes knowledge of biomarkers for RSV disease in adults. METHODS: A literature review was performed using Ovid Medline, Embase, Global health, Scopus, and Web of Science for articles published 1946-October 2016. Nine articles were identified plus 9 from other sources. RESULTS: From observational studies of natural infection and challenge studies in volunteers, biomarkers of RSV susceptibility or disease severity in adults were: (1) lower anti-RSV neutralizing antibodies, where neutralizing antibody (and local IgA) may be a correlate of susceptibility/severity; (2) RSV-specific CD8+ T cells in bronchoalveolar lavage fluid preinfection (subjects with higher levels had less severe illness); and (3) elevated interleukin-6 (IL-6), IL-8, and myeloperoxidase levels in the airway are indicative of severe infection. CONCLUSIONS: Factors determining susceptibility to and severity of RSV disease in adults have not been well defined. Respiratory mucosal antibodies and CD8+ T cells appear to contribute to preventing infection and modulation of disease severity. Studies of RSV pathogenesis in at-risk populations are needed

Global and regional burden of hospital admissions for pneumonia in older adults::A systematic review and meta-analysis

Pneumonia constitutes a substantial disease burden among adults overall and those who are elderly. We aimed to identify all studies investigating the disease burden among older adults (age, ≥65 years) admitted to the hospital with pneumonia. We estimated the hospital admission rate and in-hospital case-fatality ratio (CFR) of pneumonia in older adults, stratified by age and economic status (industrialized vs developing), with data from a systematic review of studies published from 1996 through 2017 and from 8 unpublished population-based studies. We applied these rate estimates to population estimates for 2015 to calculate the global and regional burden in older adults who would have been admitted to the hospital with pneumonia that year. We estimated the number of in-hospital pneumonia deaths by combining in-hospital CFRs with hospital admission estimates from hospital-based studies. We identified 109 eligible studies; 73 used clinical pneumonia as the case definition, and 36 used radiologically confirmed pneumonia as the case definition. We estimated that, in 2015, 6.8 million episodes (uncertainty range [UR], 5.8-8.0 episodes) of clinical pneumonia resulted in hospital admissions of older adults worldwide. The hospital admission rate increased with advancing age and was higher in men. The total disease burden was likely underestimated when using the definition of radiologically confirmed pneumonia. Based on data from 52 hospital studies reporting data on pneumonia mortality, we estimated that about 1.1 million in-hospital deaths (UR, 0.9-1.4 in-hospital deaths) occurred among older adults. The burden of pneumonia requiring hospitalization among older adults is substantial. Appropriate prevention and management strategies should be developed to reduce its impact

Single-cell immune profiling reveals markers of emergency myelopoiesis that distinguish severe from mild respiratory syncytial virus disease in infants

Whereas most infants infected with respiratory syncytial virus (RSV) show no or only mild symptoms, an estimated 3 million children under five are hospitalized annually due to RSV disease. This study aimed to investigate biological mechanisms and associated biomarkers underlying RSV disease heterogeneity in young infants, enabling the potential to objectively categorize RSV-infected infants according to their medical needs. Immunophenotypic and functional profiling demonstrated the emergence of immature and progenitor-like neutrophils, proliferative monocytes (HLA-DRLow, Ki67+), impaired antigen-presenting function, downregulation of T cell response and low abundance of HLA-DRLow B cells in severe RSV disease. HLA-DRLow monocytes were found as a hallmark of RSV-infected infants requiring hospitalization. Complementary transcriptomics identified genes associated with disease severity and pointed to the emergency myelopoiesis response. These results shed new light on mechanisms underlying the pathogenesis and development of severe RSV disease and identified potential new candidate biomarkers for patient stratification

Low Sensitivity of BinaxNOW RSV in Infants

BACKGROUND: Respiratory syncytial virus (RSV) is a major cause of hospitalization in infants. Early detection of RSV can optimize clinical management and minimize use of antibiotics. BinaxNOW RSV (BN) is a rapid antigen detection test that is widely used. We aimed to validate the sensitivity of BN in hospitalized and nonhospitalized infants against the gold standard of molecular diagnosis. METHODS: We evaluated the performance of BN in infants with acute respiratory tract infections with different degrees of disease severity. Diagnostic accuracy of BN test results were compared with molecular diagnosis as reference standard. RESULTS: One hundred sixty-two respiratory samples from 148 children from October 2017 to February 2019 were studied. Sixty-six (40.7%) samples tested positive for RSV (30 hospitalizations, 31 medically attended episodes not requiring hospitalization, and 5 nonmedically attended episodes). Five of these samples tested positive with BN, leading to an overall sensitivity of BN of 7.6% (95% confidence interval [CI], 3.3%-16.5%) and a specificity of 100% (95% CI, 96.2%-100%). Sensitivity was low in all subgroups. CONCLUSIONS: We found a low sensitivity of BN for point-of-care detection of RSV infection. BinaxNOW RSV should be used and interpreted with caution

Single-cell immune profiling reveals markers of emergency myelopoiesis that distinguish severe from mild respiratory syncytial virus disease in infants.

Whereas most infants infected with respiratory syncytial virus (RSV) show no or only mild symptoms, an estimated 3 million children under five are hospitalized annually due to RSV disease. This study aimed to investigate biological mechanisms and associated biomarkers underlying RSV disease heterogeneity in young infants, enabling the potential to objectively categorize RSV-infected infants according to their medical needs. Immunophenotypic and functional profiling demonstrated the emergence of immature and progenitor-like neutrophils, proliferative monocytes (HLA-DRLow , Ki67+), impaired antigen-presenting function, downregulation of T cell response and low abundance of HLA-DRLow B cells in severe RSV disease. HLA-DRLow monocytes were found as a hallmark of RSV-infected infants requiring hospitalization. Complementary transcriptomics identified genes associated with disease severity and pointed to the emergency myelopoiesis response. These results shed new light on mechanisms underlying the pathogenesis and development of severe RSV disease and identified potential new candidate biomarkers for patient stratification

Distinct patterns of within-host virus populations between two subgroups of human respiratory syncytial virus.

Human respiratory syncytial virus (RSV) is a major cause of lower respiratory tract infection in young children globally, but little is known about within-host RSV diversity. Here, we characterised within-host RSV populations using deep-sequencing data from 319 nasopharyngeal swabs collected during 2017-2020. RSV-B had lower consensus diversity than RSV-A at the population level, while exhibiting greater within-host diversity. Two RSV-B consensus sequences had an amino acid alteration (K68N) in the fusion (F) protein, which has been associated with reduced susceptibility to nirsevimab (MEDI8897), a novel RSV monoclonal antibody under development. In addition, several minor variants were identified in the antigenic sites of the F protein, one of which may confer resistance to palivizumab, the only licensed RSV monoclonal antibody. The differences in within-host virus populations emphasise the importance of monitoring for vaccine efficacy and may help to explain the different prevalences of monoclonal antibody-escape mutants between the two subgroups

A Retrospective Cohort Study on Infant Respiratory Tract Infection Hospitalizations and Recurrent Wheeze and Asthma Risk: Impact of Respiratory Syncytial Virus

Background Infant respiratory syncytial virus infection (RSV) has been associated with asthma later in life. We explored the risk of recurrent wheeze or asthma in children with infant RSV-associated hospitalization compared to other respiratory infections. Methods We performed a retrospective cohort study using Danish national hospital discharge registers. Infants younger than 6 months, born between January 1995 and October 2018, and with a RSV hospital admission were compared to infants hospitalized for injuries, non-RSV acute upper respiratory tract infection (AURTI), pneumonia and other respiratory pathogens, nonpathogen-coded lower respiratory tract infections (LRTI), pertussis, or nonspecific respiratory infections. Infants were followed until recurrent wheeze or asthma diagnosis, death, migration, age 10 years, or study end. We estimated cumulative incidence rate ratios (CIRR) and hazard ratios (HR) adjusted for sex, age at inclusion, hospital length of stay (LOS), maternal smoking, 5-minute APGAR score (APGAR5), prematurity, and congenital risk factors (CRF). Results We included 68 130 infants, of whom 20 920 (30.7%) had RSV hospitalization. The cumulative incidence rate of recurrent wheeze or asthma was 16.6 per 1000 person-years after RSV hospitalization, higher than after injury (CIRR, 2.69; 95% confidence interval [CI], 2.48-2.92), AURTI (CIRR, 1.48; 95% CI, 1.34-1.58), or pertussis (CIRR, 2.32; 95% CI, 1.85-2.91), similar to pneumonia and other respiratory pathogens (CIRR, 1.15; 95% CI, .99-1.34) and LRTI (CIRR, 0.79; 95% CI, .60-1.04), but lower than nonspecific respiratory infections (CIRR, 0.79; 95% CI, .73-.87). Adjusted HRs for recurrent wheeze or asthma after RSV hospitalization compared to injuries decreased from 2.37 (95% CI, 2.08-2.70) for 0 to <1 year to 1.23 (95% CI, .88-1.73) for 6 to <10 years for term-born children, and from 1.48 (95% CI, 1.09-2.00) to 0.60 (95% CI, .25-1.43) for preterm-born children. Sex, maternal smoking, LOS, CRF, and APGAR5 were independent risk factors. Conclusions Infant RSV hospitalization is associated with recurrent wheeze and asthma hospitalization, predominantly at preschool age. If causal, RSV prophylaxis, including vaccines, may significantly reduce disease burden of wheeze and asthma

Biomarkers for Disease Severity in Children Infected With Respiratory Syncytial Virus: A Systematic Literature Review.

BACKGROUND: Clinical manifestations of respiratory syncytial virus (RSV) infection vary widely from mild, self-limiting illness to severe life-threatening disease. There are gaps in knowledge of biomarkers to objectively define severe disease and predict clinical outcomes. METHODS: A systematic search was performed, 1945-March 2019 in databases Ovid Medline, Embase, Global health, Scopus, and Web of Science. Risk of bias was assessed using the Cochrane tool. RESULTS: A total of 25 132 abstracts were screened and studies were assessed for quality, risk of bias, and extracted data; 111 studies met the inclusion criteria. RSV severity was correlated with antibody titers, reduced T and B cells, dysregulated innate immunity, neutrophil mobilization to the lungs and blood, decreased Th1 response, and Th2 weighted shift. Microbial exposures in respiratory tract may contribute to neutrophil mobilization to the lungs of the infants with severe RSV compared with mild RSV disease. CONCLUSIONS: Although a wide range of biomarkers have been associated with RSV disease severity, robust validated biomarkers are lacking. This review illustrates the broad heterogeneity of study designs and high variability in the definition of severe RSV disease. Prospective studies are required to validate biomarkers. Additional research investigating epigenetics, metabolomics, and microbiome holds promise for novel biomarkers

Global patterns in monthly activity of influenza virus, respiratory syncytial virus, parainfluenza virus, and metapneumovirus: a systematic analysis.

BACKGROUND: Influenza virus, respiratory syncytial virus, parainfluenza virus, and metapneumovirus are the most common viruses associated with acute lower respiratory infections in young children (&lt;5 years) and older people (≥65 years). A global report of the monthly activity of these viruses is needed to inform public health strategies and programmes for their&nbsp;control. METHODS: In this systematic analysis, we compiled data from a systematic literature review of studies published between Jan 1, 2000, and Dec 31, 2017; online datasets; and unpublished research data. Studies were eligible for inclusion if they reported laboratory-confirmed incidence data of human infection of influenza virus, respiratory syncytial virus, parainfluenza virus, or metapneumovirus, or a combination of these, for at least 12 consecutive months (or 52 weeks equivalent); stable testing practice throughout all years reported; virus results among residents in well-defined geographical locations; and aggregated virus results at least on a monthly basis. Data were extracted through a three-stage process, from which we calculated monthly annual average percentage (AAP) as the relative strength of virus activity. We defined duration of epidemics as the minimum number of months to account for 75% of annual positive samples, with each component month defined as an epidemic month. Furthermore, we modelled monthly AAP of influenza virus and respiratory syncytial virus using site-specific temperature and relative humidity for the prediction of local average epidemic months. We also predicted global epidemic months of influenza virus and respiratory syncytial virus on a 5° by 5° grid. The systematic review in this study is registered with PROSPERO, number CRD42018091628. FINDINGS: We initally identified 37 335 eligible studies. Of 21 065 studies remaining after exclusion of duplicates, 1081 full-text articles were assessed for eligibility, of which 185 were identified as eligible. We included 246 sites for influenza virus, 183 sites for respiratory syncytial virus, 83 sites for parainfluenza virus, and 65 sites for metapneumovirus. Influenza virus had clear seasonal epidemics in winter months in most temperate sites but timing of epidemics was more variable and less seasonal with decreasing distance from the equator. Unlike influenza virus, respiratory syncytial virus had clear seasonal epidemics in both temperate and tropical regions, starting in late summer months in the tropics of each hemisphere, reaching most temperate sites in winter months. In most temperate sites, influenza virus epidemics occurred later than respiratory syncytial virus (by 0·3 months [95% CI -0·3 to 0·9]) while no clear temporal order was observed in the tropics. Parainfluenza virus epidemics were found mostly in spring and early summer months in each hemisphere. Metapneumovirus epidemics occurred in late winter and spring in most temperate sites but the timing of epidemics was more diverse in the tropics. Influenza virus epidemics had shorter duration (3·8 months [3·6 to 4·0]) in temperate sites and longer duration (5·2 months [4·9 to 5·5]) in the tropics. Duration of epidemics was similar across all sites for respiratory syncytial virus (4·6 months [4·3 to 4·8]), as it was for metapneumovirus (4·8 months [4·4 to 5·1]). By comparison, parainfluenza virus had longer duration of epidemics (6·3 months [6·0 to 6·7]). Our model had good predictability in the average epidemic months of influenza virus in temperate regions and respiratory syncytial virus in both temperate and tropical regions. Through leave-one-out cross validation, the overall prediction error in the onset of epidemics was within 1 month (influenza virus -0·2 months [-0·6 to 0·1]; respiratory syncytial virus 0·1 months [-0·2 to&nbsp;0·4]). INTERPRETATION: This study is the first to provide global representations of month-by-month activity of influenza virus, respiratory syncytial virus, parainfluenza virus, and metapneumovirus. Our model is helpful in predicting the local onset month of influenza virus and respiratory syncytial virus epidemics. The seasonality information has important implications for health services planning, the timing of respiratory syncytial virus passive prophylaxis, and the strategy of influenza virus and future respiratory syncytial virus&nbsp;vaccination. FUNDING: European Union Innovative Medicines Initiative Respiratory Syncytial Virus Consortium in Europe (RESCEU).</p