Wheezing illness caused by respiratory syncytial virus and other agents

Does respiratory syncytial virus lower respiratory illness in early life cause recurrent wheeze of early childhood and asthma? Critical review of the evidence and guidance for future studies from a World Health Organization-sponsored meeting

Respiratory syncytial virus (RSV) is a leading cause of lower respiratory tract infection (LRTI) and hospitalization in infants and children globally. Many observational studies have found an association between RSV LRTI in early life and subsequent respiratory morbidity, including recurrent wheeze of early childhood (RWEC) and asthma. Conversely, two randomized placebo-controlled trials of efficacious anti-RSV monoclonal antibodies (mAbs) in heterogenous infant populations found no difference in physician-diagnosed RWEC or asthma by treatment group. If a causal association exists and RSV vaccines and mAbs can prevent a substantial fraction of RWEC/asthma, the full public health value of these interventions would markedly increase. The primary alternative interpretation of the observational data is that RSV LRTI in early life is a marker of an underlying predisposition for the development of RWEC and asthma. If this is the case, RSV vaccines and mAbs would not necessarily be expected to impact these outcomes. To evaluate whether the available evidence supports a causal association between RSV LRTI and RWEC/asthma and to provide guidance for future studies, the World Health Organization convened a meeting of subject matter experts on February 12-13, 2019 in Geneva, Switzerland. After discussing relevant background information and reviewing the current epidemiologic evidence, the group determined that: (i) the evidence is inconclusive in establishing a causal association between RSV LRTI and RWEC/asthma, (ii) the evidence does not establish that RSV mAbs (and, by extension, future vaccines) will have a substantial effect on these outcomes and (iii) regardless of the association with long-term childhood respiratory morbidity, severe acute RSV disease in young children poses a substantial public health burden and should continue to be the primary consideration for policy-setting bodies deliberating on RSV vaccine and mAb recommendations. Nonetheless, the group recognized the public health importance of resolving this question and suggested good practice guidelines for future studies.

The relationship between rhinovirus infection and acute wheezing in young children with recurrent wheezing

Asthma is a common chronic respiratory disease in childhood. The present study aims to assess the association between rhinovirus (RV) infection and acute wheezing in the occurrence of recurrent wheezing in 5-year old and younger children. A total of 109 children with recurrent wheezing and 70 children without wheezing (controls) were recruited from October 2013 to March 2015. Nasopharyngeal aspirate samples were obtained from all children. RV, human metapneumovirus (hMPV), and bocavirus (BoV) were tested by reverse transcription-polymerase chain reaction.Respiratory syncytial virus (RSV), parainfluenza virus (PIV), influenza virus (IV), and adenoviruses (ADV) were confirmed by detection of viral antigens via fluoroimmunoassay. Viral infection was more commonly detected in children with recurrent wheezing than in controls (odds ratio (OR): 6.10; 95% confidence interval (CI): 2.89–12.87). RV and RSV were found in both wheezing children and controls. However, RV was detected more in wheezing children than in controls (OR: 3.07; 95% CI: 1.37–6.90), followed by RSV (OR: 5.33; 95% CI: 1.53–18.62). Furthermore, RV more tended to infect wheezing children after infancy. Compared with children infected with other viruses, higher levels of eosinophil were found in wheezing children with RV infection ( P < 0.05). RV was the main pathogen that induced exacerbation in young children with recurrent wheezing. Furthermore, the rate of RV infection was higher in children above 1 year old. RV infection might be associated with high levels of eosinophil.

Clinical and genetic features of human metapneumovirus infection in children

BACKGROUND

Human metapneumovirus (hMPV) is one of the main pathogens responsible for respiratory tract infection in children.

METHODS

From 2011 to 2013, nasopharyngeal aspirates were obtained from Korean children and tested for hMPV on reverse transcription-polymerase chain reaction (RT-PCR). The genotype of hMPV in each sample was identified on PCR-restriction length polymorphism analysis of the fusion gene. We divided patients into three groups according to degree of fever. Patients with fever peaking at >39.5°C or lasting >7 days were classified as the high fever (HF) group; those with fevers peaking at <38.5°C and lasting <72 h were classified as the low fever (LF) group; and the other subjects were classified as the moderate fever group.

RESULTS

Among 457 samples positive for hMPV, hMPV genotype was able to be identified in 399 (87.3%); of these, A2a was found in 97 (24.3%), B1 in 186 (46.6%), and B2 in 116 (29.1%). Clinical features of hMPV infection were compared between the HF and LF groups. We classified 80 subjects into the HF group and 84 subjects into the LF group. Mean absolute neutrophil count (5625 ± 4418 vs 4072 ± 3076/μL, P = 0.010) and C-reactive protein (2.39 ± 3.39 vs 0.96 ± 1.77 mg/dL, P = 0.001) were higher in the HF group. Wheezing (5.0% vs 32.1%, P < 0.001) and dyspnea (2.5% vs 15.5%, P = 0.010) were more frequently seen in the LF group. Genotype distribution was similar in the two groups.

CONCLUSION

Two distinct clinical presentations of hMPV infection were identified in this study.