Severe viral respiratory tract infections in children

Respiratory tract infections (RTIs) are estimated to cause 703.000 deaths annually in children below five years. The majority of RTIs in children are caused by viruses, yet the number of antivirals approved for treatment of these infections is very limited. Moreover, it is sometimes complicated to distinguish between bacterial and viral RTIs, which results in overuse of antibiotics. The aim of this thesis is to improve the understanding of the causative role of respiratory viruses in children with severe RTI, with the long-term goal to improve diagnostics, facilitate the development of new antiviral drugs and reduce unnecessary antibiotic use. To achieve this, a number of specific objectives have been assessed. The spread of the Influenza A H1N1(pdm09) i.e. the swine flu pandemic was slower than expected when it reached Europe during Spring 2009. This was suggested to be due to negative viral interference by circulating rhinovirus (RV). In Paper I, children with influenza-like illness were assessed during the swine flu pandemic in 2009. Co-infections were specifically assessed in influenza-positive patients with regard to disease severity. No significant difference was found between patients with single versus viral co-infection. Co-infection with influenza and RV was not uncommon, which contradicted the proposed hypothesis of viral interference. Moreover, the study showed that several different viruses were present in the children with suspected influenza, underscoring the overlap of disease presentation of different respiratory viruses. PCR is a very sensitive method for detecting viruses, yet the significance of a finding in upper respiratory specimens has been questioned. In Paper II, we assessed the role of viruses in acute respiratory illness in a case-control study. Respiratory syncytial virus (RSV), human metapneumovirus (hMPV) and parainfluenza virus were highly associated with acute respiratory illness. In contrast, detection of other viruses was common in asymptomatic controls, showing the complexity in interpreting PCR-positivity for these viruses. Community-acquired pneumonia (CAP) is a disease that traditionally has been considered a predominantly bacterial disease. Nevertheless, successful immunization against the two major bacterial causes, Streptococcus pneumoniae and Haemophilus influenza, has contributed to a declining incidence of the disease and has likely also led to a relative increase of other etiologic agents. In Paper III, the role of viruses in CAP was assessed in another case-control study. Viruses were detected in the majority of cases and RSV, hMPV and influenza were highly associated with CAP. The study suggests that viruses have a major role in childhood CAP and indicates that viral CAP is an underdiagnosed disease. Viral RTIs affect also immunosuppressed children. Neutropenia is a common adverse effect in children receiving chemotherapeutic treatment for malignancies. The condition highly increases the risk for septicemia, and fever is sometimes the only symptom. However, in the majority of episodes of febrile neutropenia, no causative agent can be identified. In Paper IV, respiratory viruses were assessed in immunosuppressed children during episodes of febrile neutropenia. Interestingly, respiratory viruses were detected in almost half of the episodes, whereas laboratory confirmed septicemia was infrequent (9%). Moreover, the majority of children had cleared their virus at follow-up suggesting a causal relationship between the detected viruses and the episodes of febrile neutropenia. This thesis has contributed to an improved understanding of the role of viruses in severe RTIs in children stressing the urgent need for new diagnostic tests that better distinguish between viral and bacterial disease. It also forwards the need for improved treatment options and new vaccines against viral RTIs in children

Season of birth, childhood asthma and allergy in a nationwide cohort : mediation through lower respiratory infections

Background: Previous studies have suggested an association between season of birth and risk of childhood asthma and allergic disease. The association may be modified by birth year and region, or mediated by respiratory tract infections. Objective: We aimed to estimate the association between season of birth and risk of childhood asthma/wheeze or allergic rhinoconjunctivitis in a population-based setting, and the mediating effect of lower respiratory infections. Methods: Two population-based cohorts were identified from the nationwide Swedish Medical Birth, Patient and Prescribed Drug Registers. The association between birth month/season and asthma/wheeze incidence was analysed using Cox proportional regression in the younger cohort born 2005-2010 (n = 582 494) and asthma/allergic rhinoconjunctivitis prevalence during the 7th year of life using log-binomial models in the older cohort born 2001-2004 (n = 367 583). Interactions were formally tested. Mediation analyses to address the effect of lower respiratory infections were performed in the older cohort using the R package "medflex." Results: Children born during fall and winter had an increased risk of asthma/wheeze after 2 years of age in the younger cohort: hazard ratio 1.24 (95% confidence interval, CI 1.17, 1.33) for winter and risk of prevalent asthma during their 7th year of life in the older cohort; prevalence ratio (PR) 1.12 (95% CI 1.08, 1.16) for winter. These estimates were partly mediated by lower respiratory infections; the indirect effect for winter compared with summer was PR 1.03 (95% CI 1.03, 1.04). The association was similar for allergic rhinoconjunctivitis in the 7th year of life, but not mediated by respiratory infections.Conclusion: We found that the association between season of birth and risk of childhood asthma/wheeze, but not allergic rhinoconjunctivitis, is partly mediated through lower respiratory infections. Clinical relevance: This has important implications for patient care, such as asthma management programmes to notify timing of seasonality for viral respiratory tract infections.Swedish Research Council for Health, Working Life and Welfare, Grant/Award Number: 2015-00289Swedish Research Council, Grant/Award Number: 2018-02640 and 340-2013-5867Swedish HeartLung Foundation, Grant/Award Number: 20150440 and 20180512Stockholm County CouncilKarolinska InstitutetAccepte

Etiology of Clinical Community-Acquired Pneumonia in Swedish Children Aged 1-59 Months with High Pneumococcal Vaccine Coverage-The TREND Study

(1) Immunization with pneumococcal conjugate vaccines has decreased the burden of community-acquired pneumonia (CAP) in children and likely led to a shift in CAP etiology. (2) The Trial of Respiratory infections in children for ENhanced Diagnostics (TREND) enrolled children 1-59 months with clinical CAP according to the World Health Organization (WHO) criteria at Sachs' Children and Youth Hospital, Stockholm, Sweden. Children with rhonchi and indrawing underwent "bronchodilator challenge". C-reactive protein and nasopharyngeal PCR detecting 20 respiratory pathogens, were collected from all children. Etiology was defined according to an a priori defined algorithm based on microbiological, biochemical, and radiological findings. (3) Of 327 enrolled children, 107 (32%) required hospitalization; 91 (28%) received antibiotic treatment; 77 (24%) had a chest X-ray performed; and 60 (18%) responded to bronchodilator challenge. 243 (74%) episodes were classified as viral, 11 (3%) as mixed viral-bacterial, five (2%) as bacterial, two (0.6%) as atypical bacterial and 66 (20%) as undetermined etiology. After exclusion of children responding to bronchodilator challenge, the proportion of bacterial and mixed viral-bacterial etiology was 1% and 4%, respectively. (4) The novel TREND etiology algorithm classified the majority of clinical CAP episodes as of viral etiology, whereas bacterial etiology was uncommon. Defining CAP in children <5 years is challenging, and the WHO definition of clinical CAP is not suitable for use in children immunized with pneumococcal conjugate vaccines

HIV-Neutralizing Activity of Cationic Polypeptides in Cervicovaginal Secretions of Women in HIV-Serodiscordant Relationships

HIV exposed seronegative (HESN) women represent the population most in need of a prophylactic antiviral strategy. Mucosal cationic polypeptides can potentially be regulated for this purpose and we here aimed to determine their endogenous expression and HIV neutralizing activity in genital secretions of women at risk of HIV infection.Cervicovaginal secretions (CVS) of Kenyan women in HIV-serodiscordant relationships (HESN, n = 164; HIV seropositive, n = 60) and low-risk controls (n = 72) were assessed for the cationic polypeptides HNP1–3, LL-37 and SLPI by ELISA and for HIV neutralizing activity by a PBMC-based assay using an HIV primary isolate. Median levels of HNP1–3 and LL-37 in CVS were similar across study groups. Neither HSV-2 serostatus, nor presence of bacterial vaginosis, correlated with levels of HNP1–3 or LL-37 in the HESN women. However, an association with their partner's viral load was observed. High viral load (>10,000 HIV RNA copies/ml plasma) correlated with higher levels of HNP1–3 and LL-37 (p = 0.04 and 0.03, respectively). SLPI was most abundant in the low-risk group and did not correlate with male partner's viral load in the HESN women. HIV neutralizing activity was found in CVS of all study groups. In experimental studies, selective depletion of cationic polypeptides from CVS rendered the remaining CVS fraction non-neutralizing, whereas the cationic polypeptide fraction retained the activity. Furthermore, recombinant HNP1–3 and LL-37 could induce neutralizing activity when added to CVS lacking intrinsic activity.These findings show that CVS from HESN, low-risk, and HIV seropositive women contain HIV neutralizing activity. Although several innate immune proteins, including HNP1–3 and LL-37, contribute to this activity these molecules can also have inflammatory properties. This balance is influenced by hormonal and environmental factors and in the present HIV serodiscordant couple cohort study we show that a partner's viral load is associated with levels of such molecules

Frequent Respiratory Viral Infections in Children with Febrile Neutropenia - A Prospective Follow-Up Study.

OBJECTIVE:Febrile neutropenia is common in children undergoing chemotherapy for the treatment of malignancies. In the majority of cases, the cause of the fever is unknown. Although respiratory viruses are commonly associated with this condition, the etiologic significance of this finding remains unclear and is therefore the subject of this study. STUDY DESIGN:Nasopharyngeal aspirates were collected during 87 episodes of febrile neutropenia in children age 0-18 years, being treated at a children's oncology unit between January 2013 and June 2014. Real-time polymerase chain reaction was used to determine the presence of 16 respiratory viruses. Follow-up samples were collected from children who tested positive for one or more respiratory viruses. Rhinoviruses were genotyped by VP4/VP2 sequencing. Fisher's exact test and Mann-Whitney U test were used for group comparisons. RESULTS:At least one respiratory virus was detected in samples from 39 of 87 episodes of febrile neutropenia (45%), with rhinoviruses the most frequently detected. Follow-up samples were collected after a median of 28 days (range, 9-74 days) in 32 of the 39 virus-positive episodes. The respiratory viral infection had resolved in 25 episodes (78%). The same virus was detected at follow-up in one coronavirus and six rhinovirus episodes. Genotyping revealed a different rhinovirus species in two of the six rhinovirus infections. CONCLUSION:The frequency of respiratory viral infections in this group of patients suggests an etiologic role in febrile neutropenia. However, these findings must be confirmed in larger patient cohorts

Etiology of Clinical Community-Acquired Pneumonia in Swedish Children Aged 1-59 Months with High Pneumococcal Vaccine Coverage : The TREND Study

(1) Immunization with pneumococcal conjugate vaccines has decreased the burden of community-acquired pneumonia (CAP) in children and likely led to a shift in CAP etiology. (2) The Trial of Respiratory infections in children for ENhanced Diagnostics (TREND) enrolled children 1-59 months with clinical CAP according to the World Health Organization (WHO) criteria at Sachs' Children and Youth Hospital, Stockholm, Sweden. Children with rhonchi and indrawing underwent "bronchodilator challenge". C-reactive protein and nasopharyngeal PCR detecting 20 respiratory pathogens, were collected from all children. Etiology was defined according to an a priori defined algorithm based on microbiological, biochemical, and radiological findings. (3) Of 327 enrolled children, 107 (32%) required hospitalization; 91 (28%) received antibiotic treatment; 77 (24%) had a chest X-ray performed; and 60 (18%) responded to bronchodilator challenge. 243 (74%) episodes were classified as viral, 11 (3%) as mixed viral-bacterial, five (2%) as bacterial, two (0.6%) as atypical bacterial and 66 (20%) as undetermined etiology. After exclusion of children responding to bronchodilator challenge, the proportion of bacterial and mixed viral-bacterial etiology was 1% and 4%, respectively. (4) The novel TREND etiology algorithm classified the majority of clinical CAP episodes as of viral etiology, whereas bacterial etiology was uncommon. Defining CAP in children &lt;5 years is challenging, and the WHO definition of clinical CAP is not suitable for use in children immunized with pneumococcal conjugate vaccines

Respiratory Viruses in Hospitalized Children with Influenza-Like Illness during the H1n1 2009 Pandemic in Sweden

<div><h3>Background</h3><p>The swine-origin influenza A(H1N1)pdm09 pandemic of 2009 had a slower spread in Europe than expected. The human rhinovirus (HRV) has been suggested to have delayed the pandemic through viral interference. The importance of co-infections over time during the pandemic and in terms of severity of the disease needs to be assessed.</p> <h3>Objective</h3><p>The aim of this study was to investigate respiratory viruses and specifically the presence of co-infections with influenza A(H1N1)pdm09 (H1N1) in hospitalized children during the H1N1 pandemic. A secondary aim was to investigate if co-infections were associated with severity of disease.</p> <h3>Methods</h3><p>A retrospective study was performed on 502 children with influenza-like illness admitted to inpatient care at a pediatric hospital in Stockholm, Sweden during the 6 months spanning the H1N1 pandemic in 2009. Respiratory samples were analyzed for a panel of 16 viruses by real-time polymerase chain reaction.</p> <h3>Results</h3><p>One or more viruses were detected in 61.6% of the samples. Of these, 85.4% were single infections and 14.6% co-infections (2–4 viruses). The number of co-infections increased throughout the study period. H1N1 was found in 83 (16.5%) children and of these 12 (14.5%) were co-infections. HRV and H1N1 circulated to a large extent at the same time and 6.0% of the H1N1-positive children were also positive for HRV. There was no correlation between co-infections and severity of disease in children with H1N1.</p> <h3>Conclusions</h3><p>Viral co-infections were relatively common in H1N1 infected hospitalized children and need to be considered when estimating morbidity attributed to H1N1. Population-based longitudinal studies with repeated sampling are needed to improve the understanding of the importance of co-infections and viral interference.</p> </div

Severity of disease and underlying conditions in children admitted with influenza-like illness.

a<p>Renal, metabolic and gastrointestinal diseases.</p>b<p>Including gastroenteritis, ileus, metabolic acidosis, myocarditis, renal failure, encephalitis, viral meningitis and myositis.</p

Viruses detected at time of follow up.

<p>Viruses detected at time of follow up.</p

Genotyping of repeatedly rhinovirus positive samples collected during episodes of febrile neutropenia (black boxes) and at follow-up (white boxes).

<p>Genotyping of repeatedly rhinovirus positive samples collected during episodes of febrile neutropenia (black boxes) and at follow-up (white boxes).</p