Evaluation of Respiratory Viral Pathogens in Acute Asthma Exacerbations during Childhood

Objective. Common upper respiratory tract viruses are the most frequent and important causes of asthma exacerbations in both children and adults. Prospective epidemiologic studies report that up to 80% of childhood exacerbations are associated with viral upper respiratory tract infections. Materials and methods. The study group consisted of 104 children with asthma aged 3–17 years who received treatment for asthma exacerbations in our clinic between September 2009 and 2010. Nasopharyngeal and nasal swabs were obtained from all patients during an acute attack, and from the control group (31 subjects). These specimens were investigated for the presence of viral respiratory pathogens using a real-time multiplex PCR method. The patients were compared for the presence of respiratory pathogens and factors related to the severity of the asthma exacerbation. Results. A pathogenic respiratory virus was detected in 53.8% of patients in the acute exacerbation group. The most commonly encountered viral agent was Rhinovirus (35.6%). Patients who had an acute exacerbation with or without a detectable viral pathogen were compared according to the severity of the exacerbation, the need for systemic steroids, and hospitalization rates. No statistically significant difference was found. Conclusion. Although viral upper respiratory tract infections are the most common cause of asthma exacerbations, the severity level of the exacerbation seems to be independent of whether a respiratory virus has been detected.     

Differences in the spectrum of respiratory viruses and detection of human rhinovirus C in exacerbations of adult asthma and chronic obstructive pulmonary disease

BackgroundViral respiratory infections are a common cause of acute exacerbations of chronic obstructive pulmonary disease (AECOPD) and asthma. We conducted a multicenter prospective study to determine the differences in the spectrum of viruses between adults with asthma exacerbations and AECOPD and assessed the prevalence and impact of human rhinovirus (HRV)-C in adults, which is more pathogenic in children with asthma than other HRV species.MethodsNasopharyngeal and serum samples and clinical information were collected from 64 outpatients with adult asthma exacerbations and 44 outpatients with AECOPD between April 2018 and March 2020. Viral pathogens and HRV strains were identified from nasal samples by multiplex PCR and VP4/VP2 nested PCR.ResultsViral pathogens were identified in 31 patients with asthma exacerbations (48.4%) and 17 patients with AECOPD (38.6%). The most commonly detected viruses were HRV/enterovirus followed by human metapneumovirus (hMPV) in patients with asthma exacerbations, and hMPV followed by parainfluenza virus in patients with AECOPD. HRV-C was the HRV species most commonly associated with both asthma exacerbations and AECOPD. Clinical characteristics, baseline lung function, serum inflammatory chemokines, hospitalization, and systemic steroid use did not differ between HRV-C-positive patients and those positive for other HRV species.ConclusionsExacerbation-associated spectrum of viruses differed between adults with asthma exacerbations and AECOPD. HRV-C was the HRV species most often observed in adult asthma exacerbations and AECOPD, although it did not worsen patients’ clinical outcomes relative to those of patients with other HRVs. Underlying disease-specific factors may be responsible for susceptibility to respiratory viruses.Trial registrationUMIN-CTR UMIN000031934.     

Respiratory viruses, symptoms, and inflammatory markers in acute exacerbations and stable chronic obstructive pulmonary disease.

The effects of respiratory viral infection on the time course of chronic obstructive pulmonary disease (COPD) exacerbation were examined by monitoring changes in systemic inflammatory markers in stable COPD and at exacerbation. Eighty-three patients with COPD (mean [SD] age, 66.6 [7.1] yr, FEV(1), 1.06 [0.61] L) recorded daily peak expiratory flow rate and any increases in respiratory symptoms. Nasal samples and blood were taken for respiratory virus detection by culture, polymerase chain reaction, and serology, and plasma fibrinogen and serum interleukin-6 (IL-6) were determined at stable baseline and exacerbation. Sixty-four percent of exacerbations were associated with a cold occurring up to 18 d before exacerbation. Seventy-seven viruses (39 [58.2%] rhinoviruses) were detected in 66 (39.2%) of 168 COPD exacerbations in 53 (64%) patients. Viral exacerbations were associated with frequent exacerbators, colds with increased dyspnea, a higher total symptom count at presentation, a longer median symptom recovery period of 13 d, and a tendency toward higher plasma fibrinogen and serum IL-6 levels. Non-respiratory syncytial virus (RSV) respiratory viruses were detected in 11 (16%), and RSV in 16 (23.5%), of 68 stable COPD patients, with RSV detection associated with higher inflammatory marker levels. Respiratory virus infections are associated with more severe and frequent exacerbations, and may cause chronic infection in COPD. Prevention and early treatment of viral infections may lead to a decreased exacerbation frequency and morbidity associated with COPD.     

Role of viruses in exacerbations of chronic obstructive pulmonary disease

Exacerbations of chronic obstructive pulmonary disease (COPD) are a major cause of morbidity and mortality and hospital admission. Respiratory viral infections, especially rhinoviruses, are a major cause of COPD exacerbations, with upper respiratory tract infections being associated with over 50% of COPD exacerbations. The presence of an upper respiratory tract infection leads to a more severe exacerbation and a longer symptom recovery time at exacerbation. Respiratory viral infections occurring during COPD exacerbations are more likely to lead to hospitalization. Sputum inflammatory markers were found to be higher in those patients with symptoms of a common cold or where rhinovirus was detected at exacerbation, thus suggesting that viral infections lead to greater airway inflammation and thus more severe exacerbations. COPD exacerbations are associated also with systemic inflammatory effects with increases in markers such as plasma fibrinogen and interleukin-6. Respiratory viruses have also been detected when the patients are stable, and this suggests that chronic viral infection may occur. Strategies to prevent viral infection will have a significant effect on the morbidity of COPD and will improve quality of life.     

Role of viruses and atypical bacteria in exacerbations of asthma in hospitalized children: a prospective study in the Nord-Pas de Calais region (France)

We studied the role of viruses and atypical bacteria in children hospitalized with exacerbated asthma by a prospective study of children with acute asthma admitted to the Department of Pediatrics in Lille, and to 15 hospitals in the Nord-Pas de Calais region, from October 1, 1998-June 30, 1999. We included children aged 2-16 years with active asthma, defined as three or more recurrent episodes of reversible wheezing. The severity of asthma and of asthmatic exacerbations was recorded. Immunofluorescence assays (IFA) on nasopharyngeal secretions (NPS), serological tests, or both, were used for detection of influenza virus, respiratory syncytial virus (RSV), adenovirus, parainfluenza virus, and coronavirus. Polymerase chain reaction (PCR) assays on NPS were used for rhinovirus and enterovirus. Serological tests for Chlamydia pneumoniae and Mycoplasma pneumoniae were performed. A control group of asymptomatic asthmatic outpatients was examined for respiratory viruses (using IFA and PCR). Eighty-two symptomatic children (mean age, 7.9 years) were examined. Viruses were detected in 38% (enterovirus, 15.8%; rhinovirus, 12%; RSV, 7.3%). Serological tests for atypical bacteria were positive in 10% of patients (C. pneumoniae, 5%; M. pneumoniae, 5%). Among the 27 control subjects (mean age, 7.9 years), one PCR was positive for enterovirus. There was no correlation between severity of chronic asthma or asthmatic exacerbations and the diagnosis of infection. Atypical bacterial pathogen infections were linked with prolonged asthmatic symptoms. In conclusion, we confirmed the high incidence of viral infection in acute exacerbations of asthma, especially enteroviruses or rhinoviruses. Persistent clinical features were more frequently associated with atypical bacterial infections, suggesting that these infections should be investigated and treated in cases of persistent asthmatic symptoms.     

Arthritis associated with inflammatory bowel disease in children

The records of 102 children with inflammatory bowel disease (44 with ulcerative colitis, 58 with Crohn's disease) were reviewed for evidence of joint disease unassociated with erythema nodosum. Thirteen children had arthritis, four had ulcerative colitis, and nine had Crohn's disease. Arthritis tended to be pauciarticular; ankles, knees, elbows and hips were most commonly affected. In three patients arthritis preceded bowel symptoms, in two the onset of arthritis and bowel disease was concurrent, and in eight arthritis appeared after the onset of bowel symptoms. The relationship between arthritis and specific features reflecting activity and severity of the bowel disease was examined in detail. Twenty-one attacks of arthritis, ranging in duration from two days to 12 weeks (mean, 31 days) were documented. Thirteen attacks occurred when the bowel disease was symptomatic; nine occurred within one month of a flare of the bowel disease. Most exacerbations of bowel disease in patients who had arthritis were unaccompanied by joint complaints. None of the features reflecting activity or severity of the bowel disease was more common in patients with arthritis than in those without arthritis.Supported in part by grant AM 20582 from the National Institute of Arthritis, Metabolism and Digestive Diseases.     

基于病原体学的急性呼吸道感染住院患儿非细菌性病原学混合感染特点研究

目的 通过回顾性分析本院儿科急性呼吸道感染住院患儿的非细菌性病原学混合感染的特点.方法 研究2014年5月至2015年3月我院儿内科住院治疗的急性呼吸道感染患儿,于入院24 h内取静脉血2 ml应用间接免疫荧光检测9种常见呼吸道病原早期特异性抗体IgM.对所得病原学检测结果及临床资料进行统计分析.结果 患儿中总阳性率51.2％ (147/287);各病原检出率以流感病毒A占首位30.0％ (86/287),其次是流感病毒B为28.2％ (81/287).3～6岁年龄组病原检出率56.3％ (54/96)及病原混合感染率40.6％ (39/96)均最高,其中以流感病毒B合并流感病毒A的双重感染最常见(48.5％;16/33).按月份分布,8月份病原检出率最高,占80.0％ (12/15).根据病原检测结果分组,三组间临床特征发热、咳嗽、病种(上、下呼吸道感染)、住院天数及白细胞计数差异均无统计学意义.流感病毒A、流感病毒B及副流感病毒1在混合感染中阳性率较单一感染高(P＜0.05).结论 本地区儿童急性呼吸道感染病原混合感染率占有一定比例,以流感病毒A检出率占首位,流感病毒B次之.双重感染多见.多发生于3～6岁儿童,8月份为混合感染的发病高峰期.     

The role of respiratory viruses in acute and chronic asthma

Respiratory infections can have dual effects related to asthma. First, there is increasing evidence that severe infections with RSV and PIV in infancy can alter lung development and physiology to increase the risks of subsequent wheezing and asthma. Second, infections with common cold viruses and influenza commonly precipitate wheezing symptoms in children and adults who already have established asthma, and RV appears to be the most important virus in producing exacerbations of the disease. The principal mechanisms by which this occurs appears to be viral replication in epithelial cells, triggering a cascade of inflammation involving granulocytes, macrophages, T cells, and secreted cytokines and mediators. The inflammatory process, although essential to clear the infection, augments pre-existing airway inflammation in asthma, leading to increased airway obstruction and lower respiratory tract symptoms. Greater understanding of virus-induced changes in inflammation and corresponding changes in airway physiology may lead to new therapeutic approaches to the treatment and prevention of virus-induced airway dysfunction.     

Atypical pathogens and respiratory tract infections.

The atypical respiratory pathogens Chlamydia pneumoniae, Mycoplasma pneumoniae and Legionella pneumophila are now recognised as a significant cause of acute respiratory-tract infections, implicated in community-acquired pneumonia, acute exacerbations of chronic bronchitis, asthma, and less frequently, upper respiratory-tract infections. Chronic infection with C. pneumoniae is common among patients with chronic obstructive pulmonary disease and may also play a role in the natural history of asthma, including exacerbations. The lack of a gold standard for diagnosis of these pathogens still handicaps the current understanding of their true prevalence and role in the pathogenesis of acute and chronic respiratory infections. While molecular diagnostic techniques, such as polymerase chain reaction, offer improvements in sensitivity, specificity and rapidity over culture and serology, the need remains for a consistent and reproducible diagnostic technique, available to all microbiology laboratories. Current treatment guidelines for community-acquired pneumonia recognise the importance of atypical respiratory pathogens in its aetiology, for which macrolides are considered suitable first-line agents. The value of atypical coverage in antibiotic therapy for acute exacerbations of chronic bronchitis and exacerbations of asthma is less clear, while there is no evidence to suggest that atypical pathogens should be covered in antibiotic treatment of upper respiratory-tract infections.     

Childhood respiratory infections and hospital admissions for COPD

BACKGROUND: Chronic Obstructive Pulmonary Disease (COPD) exacerbations are associated with viral infections. We wished to determine if respiratory viral infection of children in the community was associated with hospital admissions of patients with exacerbations of COPD. METHODS: We collected data over a 45-month period from the Northern Ireland Regional Virus Laboratory and from a general hospital in the same locality. We studied the relationship between upper respiratory infections in children and COPD admissions. We also examined the role of school holidays. RESULTS: Correlations were seen between the frequency of all viral infections in children and the number of adult COPD hospitalizations (P<0.005). Subgroup analysis showed distinct relationships with epidemics of; influenza A (P<0.001), influenza B (P<0.05), adenovirus (P=0.05), respiratory syncytial virus (P<0.005) and hospital admissions of patients with COPD. There were significantly fewer COPD admissions in the week after the start of a school holiday period (P<0.05). CONCLUSIONS: When children are hospitalized with viral respiratory infection there is an associated rise in adult COPD admissions. This suggests exacerbations of COPD are associated with epidemics of respiratory viruses. When children are on school holidays there is a reduction in COPD admissions in the community. This provides further support for respiratory viruses in the pathogenesis of COPD exacerbations.     

Neutrophil degranulation and cell lysis is associated with clinical severity in virus-induced asthma.

Acute exacerbations of asthma are frequently caused by viral infections, but the inflammatory mechanisms in virus-induced asthma are poorly understood. The aim of the present study was to determine whether viral infection in acute asthma was associated with increased sputum neutrophil degranulation and increased cellular lysis and whether these changes are related to clinical severity. Adults (n=49) presenting to the emergency department with acute asthma were examined for infection by means of sputum direct-fluorescence antigen detection, sputum culture, and sputum polymerase chain reaction for Mycoplasma, Chlamydia and Legionella pneumophila, and all common respiratory viruses. Subjects infected with one of these agents were classed as having an infective exacerbation. Spirometry and sputum induction were performed on presentation and 4-5 weeks later. Thirty-seven subjects (76%) had virus infection and acute asthma. Those with virus infection had increased sputum neutrophils (p<0.05) and increased neutrophil elastase (p<0.05), this was related to increased elevated sputum lactate dehydrogenase (LDH). Subjects with noninfective asthma had an increase in the proportion of sputum eosinophils. Both groups had elevated sputum eosinophil cationic protein (ECP) concentrations. Higher levels of sputum LDH and ECP were associated with a longer hospital stay. Virus infection and acute asthma is associated with neutrophilic inflammation, cell lysis and more severe clinical disease.     

2665例急性上呼吸道感染患儿的病原学及临床特征

目的 分析急性上呼吸道感染儿童患者的病原学及临床特征。方法 以南方医科大学珠江医院2009年11月至2015年9月收治的2 665例急性上呼吸道感染儿童为研究对象,采用qRT-PCR方法检测临床上常见的8种呼吸道病毒(流感病毒、呼吸道合胞病毒、副流感病毒、腺病毒、人类博卡病毒、人类冠状病毒、人类偏肺病毒、鼻病毒)。结果 共检测患儿标本2 665份,其中阳性标本1 566份,总阳性率为58.8%。四个季节中8种呼吸道病毒检出率存在明显差异,并以春季最高,夏冬季次之,秋季最低。儿童呼吸道病毒感染率随着年龄增加而逐渐降低,并以0~1岁婴幼儿病毒检出率最高64.5%。男童呼吸道病毒感染率高于女童,住院患儿呼吸道病毒检出率高于门诊患儿。混合感染标本260份,占阳性标本数的16.6%,主要集中于0~3岁儿童患者标本中,并因季节而异,秋冬季节较少,而春夏季节较为普遍。咳嗽为呼吸道病毒感染的主要临床症状,咳痰和流涕次之,临床症状在8种呼吸道病毒感染患儿中存在差异。结论 本调查分析了急性上呼吸道感染患儿中8种常见呼吸道病毒的病原学及临床特征,为指导临床治疗及防控提供相关数据。     

Detection and characterization of respiratory viruses causing acute respiratory illness and asthma exacerbation in children during three different seasons (2011–2014) in Mexico City

Background

Viral infections play a significant role in causing acute respiratory infections (ARIs) and exacerbations of chronic diseases. Acute respiratory infections are now the leading cause of mortality in children worldwide, especially in developing countries. Recently, human rhinovirus (HRV) infection has been emerged as an important cause of pneumonia and asthma exacerbation.

Objectives

To determine the role of several viral agents principally, respiratory syncytial virus, and HRV in children with ARIs and their relationship with asthma exacerbation and pneumonia.

Methods

Between October 2011 and March 2014, 432 nasopharyngeal samples of children <15 years of age with ARI hospitalized at a referral hospital for respiratory diseases were tested for the presence of respiratory viruses using a multiplex RT-qPCR. Clinical, epidemiological, and demographic data were collected and associated with symptomatology and viral infections.

Results

Viral infections were detected in at least 59·7% of the enrolled patients, with HRV (26·6%) being the most frequently detected. HRV infections were associated with clinical features of asthma and difficulty in breathing such as wheezing (P = 0·0003), supraesternal (P = 0·046), and xiphoid retraction (P = 0·030). HRV subtype C (HRV-C) infections were associated with asthma (P = 0·02).

Conclusions

Human rhinovirus was the virus most commonly detected in pediatric patients with ARI. There is also an association of HRV-C infection with asthma exacerbation, emphasizing the relevance of this virus in severe pediatric respiratory disease.     

Immune Responses in Rhinovirus-Induced Asthma Exacerbations

Acute asthma exacerbations are responsible for urgent care visits and hospitalizations; they interfere with school and work productivity, thereby driving much of the morbidity and mortality associated with asthma. Approximately 80 to 85 % of asthma exacerbations in children, adolescents, and less frequently adults are associated with viral upper respiratory tract viral infections, and rhinovirus (RV) accounts for ～60–70 % of these virus-associated exacerbations. Evidence suggests that it is not the virus itself but the nature of the immune response to RV that drives this untoward response. In particular, evidence supports the concept that RV acts to exacerbate an ongoing allergic inflammatory response to environmental allergens present at the time of the infection. The interaction of the ongoing IgE- and T cell-mediated response to allergen superimposed on the innate and adaptive immune responses to the virus and how this leads to triggering of an asthma exacerbation is discussed.     

Viral infection and allergy: lower airway.

Acute asthma exacerbations in adults and children are triggered commonly by viral upper respiratory infections. The main culprits are respiratory syncytial virus and parainfluenza virus in young children and rhinovirus in older children and adults. Recent investigations in multiple laboratories have increased our understanding of the nature of this relationship. Postulated mechanisms include a viral modulation of airway epithelial and inflammatory cell function with the release of proinflammatory cytokines and mediators, airway microvascular endothelial cell function leading to airway wall edema, airway smooth muscle cell functions, and neural regulation of airway tone via either enhanced parasympathetic efferent neuronal activity, activation of the release of bronchoactive neuropeptides from sensory c-fibers in the airways, or modulation of the influence of the nonadrenergic/noncholinergic neuronal system on airway tone. There also is evidence that rhinoviruses may directly infect the lower airways. These potential mechanisms likely relate to, are superimposed on, and potentiate preexisting inflammatory and immune responses that are characteristic of the atopic asthmatic airway. Undoubtedly, future efforts will be aimed at the prevention of asthma exacerbations via well-targeted and well-conceived strategies for prevention and/or treatment of upper respiratory infections.     

Clinical and molecular epidemiology of human bocavirus in respiratory and fecal samples from children in Hong Kong

BACKGROUND: Human bocavirus (HBoV) is a recently discovered parvovirus associated with respiratory tract infections in children. We conducted the first systematic prospective clinical and molecular study using nasopharyngeal aspirates (NPAs) and fecal samples. METHODS: NPAs negative for influenza virus, parainfluenza virus, respiratory syncytial virus, adenovirus, and coronavirus and fecal samples from patients with acute gastroenteritis were included. On the basis of results from a pilot study using 400 NPAs from all age groups, a prospective 12-month study was conducted to detect HBoV in 1,200 NPAs and 1,435 fecal samples from patients <18 years old by polymerase chain reaction. The complete genome sequences of HBoVs from 12 NPAs and 12 fecal samples were determined. RESULTS: Of the 400 NPAs collected in the pilot study, 20 (5.0%) were found to contain HBoV, all from children <5 years old. In the subsequent prospective study of pediatric patients, HBoV was detected in 83 (6.9%) of 1,200 NPAs. Upper and lower respiratory tract infections were equally common. HBoV was detected in 30 (2.1%) of 1,435 fecal samples. Fever and watery diarrhea were the most common symptoms. The seasonality of HBoV in NPAs and fecal samples was similar. Codetection with other pathogens occurred in 33% and 56% of NPAs and fecal samples, respectively, from patients with HBoV infection. Genomes of HBoVs from NPAs and fecal samples displayed minimal sequence variations. CONCLUSIONS: HBoV was detected in fecal specimens in children with acute gastroenteritis. A single lineage of HBoV was associated with both respiratory tract and enteric infections.     

Fecal leukocytosis,indium-111-labelled autologous polymorphonuclear leukocyte abdominal scanning,and quantitative fecal indium-111 excretion in acute gastroenteritis and enteropathogen carriage

Abdominal scintiscans were performed and three-day fecal indium-111 radioactivity measured, following injection of indium-111-labeled polymorphonuclear leukocytes, in patients with acute gastroenteritis, enteropathogen carriage, exacerbations of chronic inflammatory bowel disease, and patients without gastrointestinal symptoms. The colon was more commonly inflamed than the small intestine in acute gastroenteritis. Fecal indium-111 radioactivity excretion was elevated in gastroenteritis and in chronic inflammatory bowel disease. The magnitude of the intestinal inflammatory response, as measured by fecal indium-111 excretion, is equivalent in acute gastroenteritis caused by a defined enteropathogen and exacerbations of chronic inflammatory bowel disease. All patients with microscopically detected fecal leukocytosis gave positive intestinal scintiscans, whereas negative scans were obtained on patients without fecal leukocytosis. The results of this study suggest that indium-111-labeled polymorphonuclear leukocytes can be used to study pathophysiology of the enteric inflammatory response in acute infectious gastroenteritis.T.K. was partly supported by a grant from the Medical School, University of Athens. G.E.G. acknowledges support from the Wellcome Trust.     

Do life events or depression exacerbate inflammatory bowel disease? A prospective study

OBJECTIVE: To determine whether depressed mood or life events are associated with an exacerbation of inflammatory bowel disease. DESIGN: A prospective study of a consecutive sample of patients with relapsing inflammatory bowel disease, followed by monthly questionnaires and periodic office visits. SETTING: A referral-based gastroenterology clinic at a medical school. PATIENTS: A consecutive sample of 32 patients with inflammatory bowel disease who had had at least one relapse in a 2-year period after entry into the study. MEASUREMENTS AND MAIN RESULTS: The Social Readjustment Rating Scale (measuring life events), the Beck Depression Inventory (a visual analog scale for depressed mood) and an inventory of intestinal symptoms were completed monthly by each subject with a 78% rate of compliance. A mean of 2.2 exacerbations was seen per subject during the study period. Life events were not temporally associated with changes in intestinal symptoms. Significant associations were found between intestinal symptoms and the two mood scales (P less than 0.05 for each), but no directionality in symptom occurrence could be detected in a time-lagged analysis. The results were similar when the months preceding exacerbations of inflammatory bowel disease were analyzed separately. CONCLUSIONS: Although these findings suggest that mood changed concurrently with exacerbation of inflammatory bowel disease, no evidence indicated that stressful life events or depressed mood precipitated exacerbations in this study group.     

Burden of pediatric influenza A virus infection post swine-flu H1N1 pandemic in Egypt

ObjectiveTo screen children with influenza like illness or with symptoms of acute respiratory tract infections for influenza A virus infection — post swine flu pandemic era — using rapid influenza diagnostic tests.MethodsDuring two years (2010 & 2011), 1 200 children with influenza like illness or acute respiratory tract infections (according to World Health Organization criteria) were recruited. Their ages ranged from 2-60 months. Nasopharyngeal aspirates specimens were collected from all children for rapid influenza A diagnostic test.ResultsInfluenza A virus rapid test was positive in 47.5% of the children; the majority (89.6%) were presented with lower respiratory tract infections. Respiratory rate and temperature were significantly higher among positive rapid influenza test patients.ConclusionsInfluenza A virus infection is still a major cause of respiratory tract infections in Egyptian children. It should be considered in all cases with cough and febrile episodes and influenza like symptoms even post swine flu pandemic.     

Differential recruitment of dendritic cells and monocytes to respiratory mucosal sites in children with influenza virus or respiratory syncytial virus infection

BACKGROUND: Influenza virus and respiratory syncytial virus (RSV) are among the most common viruses causing infections of the lower respiratory tract in young children. Although there are important differences in the immunopathogenesis of these 2 viral pathogens, little is known about how they affect antigen-presenting cells in children with acute infections. METHODS: To characterize the immune cells that are mobilized to the respiratory tract by influenza virus and RSV, we analyzed nasal wash and blood samples obtained from children hospitalized with acute respiratory infections. RESULTS: Influenza virus and RSV mobilize immune cells, including myeloid dendritic cells (mDCs) and plasmacytoid dendritic cells (pDCs), to the nasal mucosa. Patients with influenza virus infection had greater numbers of mDCs, pDCs, and monocytes in nasal wash samples than did patients with RSV infection. The frequencies of respiratory tract and blood T cell subsets were not affected by infection with influenza virus or RSV. Monocyte chemoattractant protein-1 concentrations in nasal wash samples were significantly increased in patients with influenza virus infection but not in those with RSV infection. RANTES (regulated on activation, normally T cell expressed and secreted) concentrations were increased only in the blood of patients with influenza virus infection. CONCLUSIONS: Infection with influenza virus or RSV mobilizes antigen-presenting cells to the respiratory tract. The differences in antigen-presenting cell numbers and cytokine concentrations suggest that there are distinctive, early immune responses to these 2 viruses.