Evaluation of nasal levels of interferon and clinical severity of influenza in children.

BACKGROUND: Experimental data show that type I interferon has a key role in innate immune response against influenza infection. OBJECTIVE: We compared nasal levels of interferon-α2 and ß among inpatients and outpatients with influenza. STUDY DESIGN: Children younger than 5 years of age with influenza-like illness seeking care at the emergency department within the first 72 h of disease onset were prospectively included. Clinical and demographic data and secretions through nasal wash were obtained. Influenza infection was assessed through reverse-transcription polymerase chain reaction and nasal levels of interferon-α2 and ß were measured by enzyme-linked immunosorbent assay. All patients followed until the end of the disease. RESULTS: One hundred patients were included, of which 24 had confirmed influenza infection, and 5 of them were hospitalized. Subtypes A (H3N2) and B were confirmed in 10 and 14 patients, respectively. Seventy-six patients without influenza, including 48% of outpatients, were recruited as controls. All hospitalized patients were significantly younger regardless of influenza status (age <6 months in 59% vs. 23.2%, p < 0.001). All other data were similar among the groups. Comparing median levels of interferon-α2 among children with influenza, levels were significantly higher in outpatients than in hospitalized patients and were 263.2 pg/mL (25-75 interquartile range: 58.3-634) and detectable in only one patient (90 pg/mL), respectively. The levels of interferon-α2 in controls and those of interferon-ß in all groups were not detected. CONCLUSIONS: Higher levels of interferon-α2 in patients with less severe influenza reinforce experimental evidence about the protective role of interferon-α2 against influenza infection.

Respiratory viral coinfection and disease severity in children: A systematic review and meta-analysis.

BACKGROUND: With advent of molecular diagnostic technologies, studies have reported detection of two or more respiratory viruses in about 30% of children with respiratory infections. However, prognostic role of coinfection remains unclear. OBJECTIVE: Evaluate relation between respiratory viral confection and illness severity in children. STUDY DESIGN: MEDLINE (through PUBMED), EMBASE, EBSCO, LILACS databases were searched up to March 2015 by two independent reviewers. Studies assessing severity of viral coinfection in patients aged less than 18 years were included. Standardized forms were used for data extraction of population, study design, clinical syndromes, virus combinations compared and severity outcomes. Risk of bias and quality of evidence were assessed through EPHPP and GRADE. Subgroup analysis was performed according to age and viral combinations. RESULTS: Of 5218 records screened, 43 were included in analysis. Viral coinfection did not influence risks of all outcomes assessed: length of stay (mean difference in days in coinfection, -0.10 [95% confidence interval: -0.51 to 0.31]), length of supplemental oxygen (-0.42 [-1.05 to 0.20]), need of hospitalization (odds ratio of coinfection, 0.96 [95% confidence interval: 0.61-1.51]), supplemental oxygen (0.94 [0.66 to 1.34]), need of intensive care (0.99 [0.64 to 1.54]), mechanical ventilation (0.81 [0.33 to 2.01]) and death (2.22 [0.83 to 5.95]). Sub-analyses according to age and viral combinations have not shown influence of these factors in outcomes. CONCLUSIONS: Respiratory viral coinfection did not increase severity in all outcomes assessed. Further studies are necessary to confirm this finding, especially regarding role of specific viral interactions.