Respiratory virus infections in bone marrow transplant recipients: the European perspective

Epidemiologic Characteristics and Clinical Significance of Respiratory Viral Infections Among Adult Patients Admitted to the Intensive Care Unit

Background

The diagnosis of respiratory viral infections (RVIs) in critically ill patients is important for determining treatment options and adhering to infection-control protocols. However, data on the incidence and occurrence patterns of RVIs are scarce. We investigated the epidemiology and clinical impact of RVIs in critically ill patients.

Methods

This retrospective observational study was conducted in a tertiary hospital in South Korea between November 2014 and September 2020. Adult patients (≥ 18 years of age) who tested positive for an RVI by multiplex polymerase chain reaction (mPCR) and were admitted to the intensive care unit (ICU) were included in the study. Clinical characteristics and outcomes were obtained by reviewing electronic medical records. Pearson's χ2 test and Fisher's exact test, Mann-Whitney U test was used to compare between groups of patients. Trend analysis and the χ2-based Q test was used to analyze test behavior of physicians performing mPCR test.

Results

Among 22,517 patients admitted to the ICU during the study period, 2,222 (9.9%) underwent mPCR testing for an RVI. The median timing of mPCR testing after ICU admission was 1 day (IQR, 0-2). A total of 335 (15.1%) non-duplicative RVI-positive cases were included in the analysis. The incidence rate of RVIs in ICU patients was 30.45 per 10,000 patient-days. The most frequently detected RVI was influenza A (27.8%), followed by rhinovirus (25.4%). Thirty-two (9.6%) RVI-positive patients were diagnosed with upper respiratory infections, 193 (64.1%) with community-acquired, and 108 (35.9%) with hospital-acquired pneumonia. All-cause mortality and mortality related to respiratory tract infection (RTI) were 30.7% and 22.1%, respectively. The initial presentation of septic shock, requirement for mechanical ventilation, and lymphocytopenia were significant predictors of RTI-related mortality. Of the RVI-positive patients, 151 (45.1%) had nonviral coinfections and presented with higher clinical severity and longer hospital stays than patients infected solely with viral pathogens.

Conclusion

The incidence of RVIs in ICU patients is common. ICU patients with RVIs had high mortality and frequently presented with coinfections with nonviral pathogens, which were associated with a higher clinical severity than sole RVI. Increased testing for RVIs will enhance infection-control efforts and improve patient care.

High mortality of COVID-19 early after allogeneic stem cell transplantation – a retrospective multicenter analysis on behalf of the German Cooperative Transplant Study Group

Recipients of allogeneic stem cell transplantation (alloSCT) are at high risk for contracting infectious diseases with high morbidity and mortality. Coronavirus disease 2019 (COVID-19) is a viral respiratory disease that can lead to severe pneumonia and acute respiratory distress syndrome, with a potentially fatal outcome. In this retrospective study conducted on behalf of the German Cooperative Transplant Study Group, we aimed to analyze risk factors, disease course, and outcomes of COVID-19 in patients who underwent alloSCT. AlloSCT recipients who became infected with SARS-CoV-2 at German and Austrian transplant centers between February 2020 and July 2021 were included. Classification of COVID-19 severity into mild, moderate-severe, or critical disease and division of the course of the pandemic into 4 phases were done according to the German Robert Koch Institute. The main endpoint was overall mortality at the end of follow-up. We further analyzed the need for treatment in an intensive care unit (ICU) and the severity of disease. Risk factors were evaluated using univariate and multivariate analyses, and survival analysis was performed using Kaplan-Meier method. The study cohort comprised 130 patients from 14 transplant centers, with a median age at diagnosis of COVID-19 of 59 years (range, 20 to 81 years) and a median interval between alloSCT and COVID-19 of 787 days (range, 19 to 8138 days). The most common underlying diseases were acute myeloid leukemia (45.4%) and lymphoma (10.8%). The majority of patients (84.9%) were infected in the later phases of the pandemic; 20.8% had moderate-severe disease, 12.3% had critical disease, and 19.2% were treated in an ICU. After a median follow-up of 127 days, overall mortality was 16.2%, 52.0% among patients treated in an ICU. Risk factors for mortality in multivariate analysis were active disease (odds ratio [OR], 4.46), infection with SARS-CoV-2 ≤365 days after alloSCT (OR, 5.60), age >60 years (OR, 5.39), and ongoing immunosuppression with cyclosporine (OR, 8.55). Risk factors for developing moderate-severe or critical disease were concurrent immunosuppression (OR, 4.06) and age >40 years (OR, 4.08). Patients after alloSCT exhibit a substantially increased mortality risk after COVID-19 infection compared with the normal population, without considerable improvement over the course of the pandemic. Risk factors include age, early infection post-alloSCT, and active immunosuppression. Further studies are needed to improve prevention and treatment in this high-risk patient group.

Phenotypes, Lung Microbiota and Cytokine Responses in Pneumonia After Hematopoietic Stem Cell Transplantation

Objective

We aim to identify phenotypes of hematopoietic stem cell transplantation (HSCT) patients with pneumonia, discover relations of microbiota composition, cytokine profile, and outcomes between phenotypes. Specific cytokines will be evaluated for their role in lung injury in a murine model.

Methods

HSCT patients with pneumonia were included, and clustering of variables including cytokine levels provided the phenotypes. Outcomes were compared between phenotypes. Analysis of lung microbiota identified marker species of phenotypes. In the murine model, marker species-related cytokine regulations and the role of cytokines in lung injury were evaluated.

Results

Seventy-two patients were included, and two phenotypes were identified, namely "reactive" (N=21) and "nonreactive" (N=51) phenotype. Compared to their counterparts, patients with nonreactive phenotype had lower serum IL-6, IL-8, less severe inflammation, worse outcomes and more viruses as marker species in lung microbiota. The animal study validated the pathogens specific cytokine responses that presented in the human study and the potential protective role of IL-6 in these patients.

Conclusion

HSCT patients with pneumonia can be clustered into two phenotypes with different marker species and outcomes: the "nonreactive" phenotype and the "reactive" phenotype. Serum cytokine levels were different between the two phenotypes, which indicate the existence of the pathogen-related cytokine responses. For patients with the "nonreactive" phenotype, IL-6 therapy may improve their prognosis, which should be further tested in clinical studies.

Incidence and impact of community respiratory viral infections in post-transplant cyclophosphamide-based graft-versus-host disease prophylaxis and haploidentical stem cell transplantation

Community respiratory viral infections (CRVIs) are associated with pulmonary function impairment, alloimmune lung syndromes and inferior survival in human leucocyte antigen (HLA)-matched allogeneic haematopoietic stem cell transplant (HCT) recipients. Although the incidence of viral infections in HLA-haploidentical HCT recipients who receive post-transplant cyclophosphamide (PTCy)-based graft-versus-host disease (GVHD) prophylaxis is reportedly increased, there are insufficient data describing the incidence of CRVIs and the impact of donor source and PTCy on transplant outcomes. Analysing patients receiving their first HCT between 2012 and 2017 for acute myeloid leukaemia, acute lymphoblastic leukaemia and myelodysplastic syndromes, we describe comparative outcomes between matched sibling transplants receiving either calcineurin-based GVHD prophylaxis (SibCNI, N = 1605) or PTCy (SibCy, N = 403), and related haploidentical transplants receiving PTCy (HaploCy, N = 757). The incidence of CRVIs was higher for patients receiving PTCy, regardless of donor type. Patients in the HaploCy cohort who developed a CRVI by day +180 had both a higher risk of treatment-related mortality [hazard ratio (HR) 2⋅14, 99% confidence interval (CI) 1⋅13-4⋅07; P = 0⋅002] and inferior 2-year overall survival (HR 1⋅65, 99% CI 1⋅11-2⋅43; P = 0⋅001) compared to SibCNI with no CRVI. This finding justifies further research into long-term antiviral immune recovery, as well as development of preventive and treatment strategies to improve long-term outcomes in such patients.

Impact of Influenza Infection Among Adult and Pediatric Populations With Hematologic Malignancy and Hematopoietic Stem Cell Transplant: A Systematic Review and Meta-Analysis

PURPOSE

Influenza is increasingly recognized as a leading cause of morbidity and mortality in patients with hematologic malignancies and recipients of hematopoietic stem cell transplantation (HSCT). However, the impact of influenza on this population has not been previously evaluated in a systematic review. This study systematically reviewed and summarized the outcomes of influenza infection as to in-hospital influenza-related mortality, development of lower respiratory tract infection and acute respiratory distress syndrome, need for hospitalization, intensive care unit admission, and mechanical ventilation.

METHODS

We conducted a systematic search of literature using the PubMed and EMBASE databases for articles published from January 1989 through January 19, 2020, reporting laboratory-confirmed influenza in patients of any age with hematologic malignancies and HSCT. Time from transplantation was not included in the search criteria. The impact of antiviral therapy on influenza outcomes was not assessed due to heterogeneity in antiviral treatment provision across the studies. Patients with influenza-like illness, solid-tumor cancers, or nonmalignant hematologic diseases were excluded from the study. A random-effects meta-analysis was performed to estimate the prevalences and 95% CIs of each outcome of interest. A subgroup analysis was carried out to assess possible sources of heterogeneity and to evaluate the potential impact of age on the influenza infection outcomes. Heterogeneity was assessed using the I² statistic.

FINDINGS

Data from 52 studies providing data on 1787 patients were included in this analysis. During seasonal epidemics, influenza-related in-hospital mortality was 16.60% (95% CI, 7.49%-27.7%), with a significantly higher death rate in adults compared to pediatric patients (19.55% [95% CI, 10.59%-29.97%] vs 0.96% [95% CI, 0%-6.77%]; P < 0.001). Complications from influenza, such as lower respiratory tract infection, developed in 35.44% of patients with hematologic malignancies and HSCT recipients, with a statistically significant difference between adults and children (46.14% vs 19.92%; P < 0.001). However, infection resulted in a higher hospital admission rate in pediatric patients compared to adults (61.62% vs 22.48%; P < 0.001). For the 2009 H1N1 pandemic, no statistically significant differences were found between adult and pediatric patients when comparing the rates of influenza-related in-hospital mortality, lower respiratory tract infection, and hospital admission. Similarly, no significant differences were noted in any of the outcomes of interest when comparing H1N1 pandemic with seasonal epidemics.

IMPLICATIONS

Regardless of influenza season, patients, and especially adults, with underlying hematologic malignancies and HSCT recipients with influenza are at risk for severe outcomes including lower respiratory tract infection and in-hospital mortality.

Clinical Effectiveness of Influenza Vaccination After Allogeneic Hematopoietic Stem Cell Transplantation: A Cross-sectional, Prospective, Observational Study

BACKGROUND

Vaccination is the primary method for preventing influenza respiratory virus infection (RVI). Although the influenza vaccine is able to achieve serological responses in some allogeneic hematopoietic stem cell transplantation (allo-HSCT) recipients, its clinical benefits are still uncertain.

METHODS

In this prospective, cross-sectional study, we retrospectively analyzed the effect of inactivated trivalent influenza vaccination on the prevalence of influenza RVI in a consecutive cohort of 136 allo-HSCT adult recipients who developed 161 RVI over 5 flu seasons (from 2013 to 2018). Respiratory viruses in upper- and/or lower-respiratory tract specimens were tested using multiplex polymerase chain reaction panel assays.

RESULTS

Overall, we diagnosed 74 episodes (46%) of influenza RVI in 70 allo-HSCT recipients. Influenza RVI occurred in 51% of the non-vaccinated compared to 36% of the vaccinated recipients (P = .036). A multivariate analysis showed that influenza vaccination was associated with a lower prevalence of influenza RVI (odds ratio [OR] 0.39, P = .01). A multivariate risk factor analysis of lower-respiratory tract disease (LRTD) identified 2 conditions associated with the probability of influenza RVI progression: influenza vaccination (OR 0.12, 95% confidence interval [CI] 0.014-1, P = .05) and a high-risk immunodeficiency score (OR 36, 95% CI 2.26-575, P = .011). Influenza vaccination was also associated with a lower likelihood of an influenza-related hospital admission (14% vs 2%, P = .04).

CONCLUSIONS

This study shows that influenza vaccination may have a clinical benefit in allo-HSCT recipients with virologically-confirmed RVI, in terms of a lower influenza RVI prevalence, slower LRTD progression, and lower likelihood of hospital admission.

Immunodeficiency risk score for prediction of mortality by parainfluenza virus infection in patients with hematologic malignancy

Parainfluenza virus (PIV) infection is a significant cause of morbidity and mortality, especially in hematologic malignancy patients including hematopoietic stem cell transplantation (HCT) recipients. However, limited information is available for risk stratification in PIV-infected patients with hematologic malignancy with or without HCT. Patients with hematologic malignancy diagnosed with PIV from January 2009 to December 2018 were retrospectively included in a tertiary care hospital in Seoul, South Korea. Upper respiratory tract infection (URTI) was defined as the detection of PIV in a nasopharyngeal sample with URTI symptoms without new pulmonary infiltrates. Lower respiratory tract infection (LRTI) was defined as detection of PIV in either upper or lower respiratory tract samples with new pulmonary infiltrates, with or without hypoxia. PIV-associated mortality was defined as death with respiratory failure and persistent LRTI within 90 days after diagnosis. The study included 143 adult patients. Of these, 55 (38%) progressed to or initially presented with LRTI. Among these, 22 (40%) died from PIV-associated mortality. An immunodeficiency risk score was developed from associated risk factors using a multivariable Cox regression model. Patients were stratified into low (0-2), moderate (3-5), and high risk (6-8) groups with PIV-associated mortalities of 0%, 9%, and 67%, respectively (p < 0.005, Harrell's C-index = 0.84). PIV infection can result in substantial mortality in patients with hematologic malignancy if it progresses to LRTI. The immunodeficiency risk score presented here may be useful for distinguishing moderate and high risk groups that might benefit from antiviral therapy.

Respiratory Virus Infections in Hematopoietic Cell Transplant Recipients

Highly immunocompromised pediatric and adult hematopoietic cell transplant (HCT) recipients frequently experience respiratory infections caused by viruses that are less virulent in immunocompetent individuals. Most of these infections, with the exception of rhinovirus as well as adenovirus and parainfluenza virus in tropical areas, are seasonal variable and occur before and after HCT. Infectious disease management includes sampling of respiratory specimens from nasopharyngeal washes or swabs as well as sputum and tracheal or tracheobronchial lavages. These are subjected to improved diagnostic tools including multiplex PCR assays that are routinely used allowing for expedient detection of all respiratory viruses. Disease progression along with high mortality is frequently associated with respiratory syncytial virus, parainfluenza virus, influenza virus, and metapneumovirus infections. In this review, we discuss clinical findings and the appropriate use of diagnostic measures. Additionally, we also discuss treatment options and suggest new drug formulations that might prove useful in treating respiratory viral infections. Finally, we shed light on the role of the state of immune reconstitution and on the use of immunosuppressive drugs on the outcome of infection.

Viral Respiratory Tract Infections in Allogeneic Hematopoietic Stem Cell Transplantation Recipients in the Era of Molecular Testing

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Rhinovirus caused the majority of vRTI episodes in first 100 days following transplantation.

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Progression to lower respiratory tract infection was seen in 30% of patients with vRTI.

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vRTI in first 100 days after transplantation is associated with morbidity (ie, ICU admission).

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All of the deaths in our study cohort occurred in patients who acquired vRTI within 30 days of transplantation.

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Previous autologous transplantation is a significant risk factor for vRTI.

Viral respiratory tract infection (vRTI) is a significant cause of morbidity and mortality in patients undergoing allogeneic hematopoietic stem cell transplantation (allo-HSCT). This study aimed to assess the epidemiologic characteristics, risk factors, and outcomes of vRTI occurring in the period from conditioning to 100 days after allo-HSCT in the era of molecular testing. This study was a retrospective record review of patients who underwent allo-HSCT at Royal Melbourne Hospital between January 2010 and December 2015. Symptomatic patients were tested using respiratory multiplex polymerase chain reaction (PCR). Logistic regression and Kaplan-Meier analysis were used to identify risk factors for vRTI and the risk of death or intensive care unit (ICU) admission, respectively. A total of 382 patients were reviewed, and 65 episodes of vRTI were identified in 56 patients (14.7%). Rhinovirus accounted for the majority of infections (69.2%). The majority of episodes presented initially with upper respiratory tract infection (58.5%), with 28.9% of them progressing to lower respiratory tract infection. Eleven episodes (16.9%) were associated with ICU admission. There were no deaths directly due to vRTI. Previous autologous HSCT was associated with an increased risk of vRTI (odds ratio, 2.1; 95% confidence interval, 1.0 to 4.1). The risks of death (P = .47) or ICU admission (P = .65) were not significantly different by vRTI status. vRTI is common in the first 100 days after allo-HSCT and is associated with ICU admission.

Viral Pneumonia in Patients with Hematologic Malignancy or Hematopoietic Stem Cell Transplantation

Viral pneumonias in patients with hematologic malignancies and recipients of hematopoietic stem cell transplantation cause significant morbidity and mortality. Advances in diagnostic techniques have enabled rapid identification of respiratory viral pathogens from upper and lower respiratory tract samples. Lymphopenia, myeloablative and T-cell depleting chemotherapy, graft-versus-host disease, and other factors increase the risk of developing life-threatening viral pneumonia. Chest imaging is often nonspecific but may aid in diagnoses. Bronchoscopy with bronchoalveolar lavage is recommended in those at high risk for viral pneumonia who have new infiltrates on chest imaging.

Respiratory Syncytial Virus and Human Metapneumovirus Infection in Transplant Recipients

Respiratory viral infections due to respiratory syncytial virus (RSV) and human metapneumovirus (hMPV) cause infections in immunocompromised transplant patients ranging from mild upper respiratory infections to severe lower respiratory tract disease with respiratory failure. These viruses are more readily diagnosed due to improvements in sensitive molecular diagnostic methods. The epidemiology of RSV and hMPV is similarly becoming more readily appreciated in hematopoietic stem cell transplant (HSCT) patients of all ages as well as solid organ transplant (SOT) patients, with lung transplant recipients having evidence of more frequent and severe complications related to these viruses. RSV and hMPV infection typically but not always present with upper respiratory signs and symptoms that progress to lower respiratory tract disease. Treatment options for RSV are limited, with aerosolized, intravenous, and oral ribavirin all studied in HSCT and lung transplant patients. No antiviral therapy for the treatment of hMPV is available, although ribavirin has shown some effectiveness in vitro. New antiviral agents including RSV fusion inhibitors and nucleoside analogs are being developed, with some under clinical evaluation.

High risk for RSV bronchiolitis in late preterms and selected infants affected by rare disorders: a dilemma of specific prevention

Respiratory syncytial virus (RSV) is the most frequent aetiologic agent that causes bronchiolitis and lower respiratory tract infection in infants. These infections may be severe and even life-threatening in selected high-risk populations. Traditional, well-established, high-risk populations are preterm infants with or without chronic lung disease and children with congenital heart disease. For these children, RSV prophylaxis using palivizumab, a monoclonal anti-RSV humanised antibody against the F-protein of RSV, has proven safe and efficacious in preventing RSV-related hospitalisation. Recently, a number of rare medical conditions have been associated with the risk of severe RSV infections. Evidence of safety and efficacy of RSV prophylaxis in these populations is lacking. Given the low incidence of these conditions, randomised trials are not feasible. A practical, opinion-based approach to this dilemma is offered in this paper. It is proposed that these rare disorders may qualify for RSV prophylaxis if the association between a specific condition and the risk of severe RSV infection is confirmed in at least 3 independent publications, of which at least 1 includes a prospective cohort study. To facilitate pharmaco-economic analyses, at least one of the three studies must also report on the absolute risk of severe RSV infection in the specified illness. The authors believe that qualification criteria will enable caregivers to target RSV prophylaxis more effectively in children with rare conditions and the proposed approach provides direction for future epidemiological studies on the risk of severe RSV infection in children with these uncommon, medical illnesses.

Respiratory viral infections in hematopoietic stem cell and solid organ transplant recipients

Respiratory viral infections (RVIs) are common causes of mild illness in immunocompetent children and adults with rare occurrences of significant morbidity or mortality. Complications are more common in the very young, very old, and those with underlying lung diseases. However, RVIs are increasingly recognized as a cause of morbidity and mortality in recipients of hematopoietic stem cell transplants (HSCT) and solid organ transplants (SOTs). Diagnostic techniques for respiratory syncytial virus (RSV), parainfluenza, influenza, and adenovirus have been clinically available for decades, and these infections are known to cause serious disease in transplant recipients. Modern molecular technology has now made it possible to detect other RVIs including human metapneumovirus, coronavirus, and bocavirus, and the role of these viruses in causing serious disease in transplant recipients is still being worked out. This article reviews the current information regarding epidemiology, pathogenesis, clinical presentation, diagnosis, and treatment of these infections, as well as the aspects of clinical significance of RVIs unique to HSCT or SOT.

Hematopoietic stem cell transplantation: an overview of infection risks and epidemiology

Hematopoietic stem cell transplantation (HSCT) is a treatment for multiple medical conditions that result in bone marrow failure and as an antineoplastic adoptive immunotherapy for hematologic malignancies. HSCT is associated with profound compromises in host barriers and all arms of innate and acquired immunity. The degree of immune compromise varies by type of transplant and over time. Immune reconstitution occurs within several months after autologous HSCT but takes up to a year or longer after allogeneic HSCT. In those patients who develop chronic graft-versus-host disease, immune reconstitution may take years or may never completely develop. Over time, with strengthening immune reconstitution and control of graft-versus-host disease, the risk for infection dissipates.

Novel influenza A (H1N1) in patients with hematologic disease

Patients with hematologic disease are likely to be at increased risk for infection with influenza. We retrospectively analyzed 11 cases of patients with hematologic disease who were infected with pandemic H1N1 virus in our department, including their clinical manifestations, laboratory and imaging findings, outcomes of antiviral therapy, and factors associated with mortality. Notably, nine patients had lower respiratory tract disease. Five patients progressed to respiratory failure and eventually died, despite treatment with antivirals and/or corticosteroids and/or mechanical ventilation. We concluded that H1N1 2009 infection was associated with a severe course and high rate of mortality in patients with hematologic disease, and early diagnosis and antiviral treatment were important to reduce the rate of severe complications and mortality.

The clinical features and outcome of 2009 H1N1 influenza infection in allo-SCT patients: a British Society of Blood and Marrow Transplantation study

The clinical course of 2009 H1N1 influenza in Allo-SCT patients is unknown. Data were collected in the UK from October 2009 to April 2010 on laboratory-confirmed cases of H1N1 influenza in Allo-SCT recipients. H1N1 infection was diagnosed in 60 patients, median age 42 years, at a median of 10 months post-SCT. Twenty-one patients (35%) developed pneumonia and nine (15%) required admission to intensive care units. Actuarial mortality was 7% at 28 days and 19% 4 months post-diagnosis of 2009 H1N1 influenza. Increasing age and pre-existing lung disease were risk factors for pneumonia (P=0.006 and 0.037, respectively); older age was a risk factor for death (P=0.012). Morbidity and mortality from 2009 H1N1 influenza in SCT patients exceeds that of immunocompetent patients, but parallels that in other critically ill hospitalised cohorts; the elderly and those with chronic pulmonary disease are at greatest risk.

Seroprotective titers against 2009 H1N1 influenza A virus after vaccination in allogeneic hematopoietic stem cell transplantation recipients

Little data are available regarding the safety and immunologic response to pandemic H1N1 influenza vaccine in recipients of allogeneic hematopoietic stem cell transplantation (HSCT). We measured serum antibody titers against A/California/7/2009 H1N1 using a hemagglutination inhibition assay in 82 allogeneic HSCT recipients who received the 2009 H1N1 vaccine between November 2009 and January 2010 after it became available at our institution. The median time between HSCT and vaccination was 19 months (range, 2.5-94 months), and the median time from vaccination to specimen collection was 56 days (range, 14-140 days). Seroprotective antibody titers (hemagglutination inhibition titer ≥1:40) against 2009 H1N1 influenza A virus were detected in 51% of patients. The presence of chronic graft-versus-host disease and type of conditioning regimen did not affect the rate of detection of seroprotective titers after vaccination. Patients were more likely to have a seroprotective titer the farther away from HSCT they were (adjusted odds ratio, 1.79 per year; 95% confidence interval, 1.12-2.85). Rituximab administration in the year before vaccination was associated with a lack of seroprotective titer (adjusted odds ratio, 0.11; 95% confidence interval, 0.01-0.97). The vaccine was safe and well tolerated. Strategies are needed to improve the influenza vaccine response in this population, especially those receiving immunotherapy.

Infections in pediatric transplant recipients: not just small adults

Transplantation increasingly is being used as treatment for children with end-stage organ diseases, hematopoietic rescue from therapy used to treat malignancies, and as cure for primary immune deficiencies. This article reviews some of the major concepts regarding infections that complicate pediatric transplantation, highlighting differences in epidemiology, evaluation, treatment and prevention for children compared with adult recipients.

Hematopoietic stem cell transplantation: an overview of infection risks and epidemiology

Hematopoietic stem cell transplantation (HSCT) is a treatment for multiple medical conditions that result in bone marrow failure and as an antineoplastic adoptive immunotherapy for hematologic malignancies. HSCT is associated with profound compromises in host barriers and all arms of innate and acquired immunity. The degree of immune compromise varies by type of transplant and over time. Immune reconstitution occurs within several months after autologous HSCT but takes up to a year or longer after allogeneic HSCT. In those patients who develop chronic graft-versus-host disease, immune reconstitution may take years or may never completely develop. Over time, with strengthening immune reconstitution and control of graft-versus-host disease, the risk for infection dissipates.

2009 H1N1 influenza infection in cancer patients and hematopoietic stem cell transplant recipients

OBJECTIVES

Although usually mild, 2009 H1N1 Influenza has caused up to 6000 deaths in the US. To determine outcome in patients with cancer and/or hematopoietic stem cell transplant (HSCT), we reviewed our recent experience at Memorial Sloan-Kettering Cancer Center (MSKCC).

METHODS

During the initial NYC outbreak (May 19-June 30, 2009), all respiratory samples at MSKCC were tested for 2009 H1N1 influenza by DFA, culture, and RT-PCR. Medical records were reviewed for all cases.

RESULTS

During the 6-week period, 45(11%) of 394 tested patients were diagnosed with 2009 H1N1 Influenza. These included 29(17%) of 167 patients with hematologic conditions compared to 16(7%) of 226 with solid tumors (P < 0.01). 21(22%) of 96 tested HSCT recipients were positive. Cough (93%) and fever (91%) were common. Of 29 patients who were radiographically assessed, 8(27%) had lower airway disease. 17(37%) were hospitalized. None required mechanical ventilation. No deaths were attributed to influenza. All treated patients tolerated antiviral medication.

CONCLUSIONS

2009 H1N1 Influenza caused mild symptoms in most patients with cancer and/or HSCT. None died or required mechanical ventilation. Immunosuppression from cancer or its treatment including HSCT may not be a substantial risk for poor outcome, however further studies are needed to validate our results.

Influenza in immunosuppressed populations: a review of infection frequency, morbidity, mortality, and vaccine responses

Patients that are immunosuppressed might be at risk of serious influenza-associated complications. As a result, multiple guidelines recommend influenza vaccination for patients infected with HIV, who have received solid-organ transplants, who have received haemopoietic stem-cell transplants, and patients on haemodialysis. However, immunosuppression might also limit vaccine responses. To better inform policy, we reviewed the published work relevant to incidence, outcomes, and prevention of influenza infection in these patients, and in patients being treated chemotherapy and with systemic corticosteroids. Available data suggest that most immunosuppressed populations are indeed at higher risk of influenza-associated complications, have a general trend toward impaired humoral vaccine responses (although these data are mixed), and can be safely vaccinated--although longitudinal data are largely lacking. Randomised clinical trial data were limited to one study of HIV-infected patients with high vaccine efficacy. Better trial data would inform vaccination recommendations on the basis of efficacy and cost in these at-risk populations.

Stem Cell Transplantation

Hematopoietic cell transplantation (HCT) is associated with profound compromises in host defenses. The patterns of immune compromise change over time. Infections are an important cause of serious morbidity and pose substantial threats to life. Thus, the challenges of infection facing the transplant clinician are both myriad and dynamic. Early after transplant, neutropenic infections are most important. Later herpesvirus and invasive fungal infections predominate. Even late after transplant, patients with chronic graft versus host disease remain susceptible to encapsulated bacterial, varicella zoster virus, and invasive fungal infections. Over time, with robust engraftment and control of GVHD, the risk of serious infections recedes with immune reconstitution.

Viral Infections of the Lung

The lungs are among the most vulnerable to microbial assault of all organs in the body. From a contemporary vantage, lower respiratory tract infections are the greatest cause of infection-related mortality in the United States, and rank seventh among all causes of deaths in the United States.2,3 From a global and historic perspective, the scope and scale of lower respiratory tract infection is greater than any other infectious syndrome, and viral pneumonias have proven to be some of the most lethal and dramatic of human diseases. The 1918–1919 influenza pandemic, perhaps the most devastating infectious disease pandemic in recorded history, resulted in an estimated 40 million deaths worldwide, including 700,000 deaths in the U.S.4 The global outbreak of severe acute respiratory syndrome (SARS) during 2003, although considerably smaller in scale, resulted in 8098 cases and 774 deaths5 and is a dramatic contemporary example of the ability of viral pneumonias to rapidly disseminate and cause severe disease in human populations.

Currently used nucleic acid amplification tests for the detection of viruses and atypicals in acute respiratory infections

For the detection of respiratory viruses conventional culture techniques are still considered as the gold standard. However, results are mostly available too late to have an impact on patient management. The latest developments include appropriate DNA- and RNA-based amplification techniques (both NASBA and PCR) for the detection of an extended number of agents responsible for LRTI. Real time amplification, the latest technical progress, produces, within a considerable shorter time, results with a lower risk of false positives. As results can be obtained within the same day, patient management with appropriate therapy or reduction of unnecessary antibiotic therapy in LRTI will be possible. A number of technical aspects of these amplification assays, and their advantages are discussed.

The availability and use of these new diagnostic tools in virology has contributed to a better understanding of the role of respiratory viruses in LRTI. The increasing importance of the viral agents, Mycoplasma pneumoniae and Chlamydophila pneumoniae in ARI is illustrated. A great proportion of ARI are caused by viruses, but their relative importance depends on the spectrum of agents covered by the diagnostic techniques and on the populations studied, the geographical location and the season. The discovery of new viruses is ongoing; examples are the hMPV and the increasing number of coronaviruses. Indications for the use of these rapid techniques in different clinical situations are discussed. Depending on the possibilities, the laboratory could optimize its diagnostic strategy by applying a combination of immunofluorescence for the detection of RSV an IFL, and a combination of real-time amplification tests for other respiratory viruses and the atypical agents. When implementing a strategy, a compromise between sensitivity, clinical utility, turn around time and cost will have to be found.

Failure of Zanamivir Therapy for Pneumonia in a Bone-Marrow Transplant Recipient Infected by a Zanamivir-Sensitive Influenza a (H1N1) Virus

Influenza A viruses are responsible for significant morbidity and mortality after bone marrow transplantation. Here we report failure of inhaled zanamivir treatment in a bone-marrow transplant recipient with pneumonia caused by an influenza A (H1N1) virus, although the influenza viruses isolated from bronchoalveolar lavages before and after treatment were clearly found to be sensitive to zanamivir using cell-based and enzymatic assays. Subsequent oral treatment with oseltamivir allowed complete recovery. Poor bioavailability of zanamivir in the peripheral lungs might have been limiting treatment efficacy in such an immunocompromised patient.

[The microbiology laboratory: a key participant in transplantation]

Together with organ rejection, infectious complications are still the most important cause of morbidity and mortality in organ transplant recipients. Many infectious complications have an exogenous origin, including those produced by organ-transmitted pathogens, whereas others are caused by latent microorganisms that become reactivated in the recipient. Accurate pre-transplantation assessment of the organ donor as well as the recipient can prevent some infectious complications or reduce their detrimental effects during the post-transplant period. A wide range of primary and opportunistic microorganisms can affect transplant recipients, and a detailed description of these pathogens is beyond the scope of this study. However, the importance of microbiology laboratories in centers with transplant programs and the need for integration and active participation of clinical microbiologists in multidisciplinary transplant teams should be emphasized. The work of these professionals is a key requisite to establish accurate diagnoses of infectious complications, which will benefit the patient and optimize the expenditure of resources.

Long-term therapy with aerosolized ribavirin for parainfluenza 3 virus respiratory tract infection in an infant with severe combined immunodeficiency

We report the case of an infant with severe combined immunodeficiency who was presented with PIV3 infection. Aerosolized ribavirin was administered for 10 months until the child gained a functional immune system through an allogeneic hematopoietic stem cell transplant and cleared PIV3 infection. No adverse effect was observed in the child and in healthcare personnel, with a follow-up of three years. Despite the burden of aerosolized administration, early and prolonged administration of aerosolized ribavirin was feasible, well tolerated, and safe for the patient and the caregivers. This is a case report and no definite conclusions can be drawn. However, our experience suggests that prolonged aerosolized ribavirin administration should be considered for the treatment of PIV3 infection in the context of primary immunodeficiency, where there is no currently available alternative treatment, until a functional immune system is gained.

Adenovirus-specific CD4+ T cell clones recognizing endogenous antigen inhibit viral replication in vitro through cognate interaction

Human adenovirus (HAdV) infection is a frequent and potentially severe complication following allogeneic stem cell transplantation in children. Because treatment with antiviral drugs is often ineffective, adoptive transfer of donor-derived HAdV-specific T cells able to control viral replication of HAdV of multiple serotypes may be an option for therapy. In healthy donors, predominantly HAdV-specific T cells expressing CD4 are detected. In this study, a preclinical in vitro model was used to measure the antiviral effect of HAdV-specific CD4+ T cells. CD4+ HAdV-specific T cell clones restricted by HLA class II molecules were generated and most of these clones recognized conserved peptides derived from the hexon protein. These cross-reactive T cell clones were able to control viral replication of multiple serotypes of HAdV in EBV-transformed B cells (B-LCL), melanoma cells (MJS) and primary bronchial epithelial cells through cognate interaction. The HAdV-specific CD4+ T cell clones were able to specifically lyse infected target cells using a perforin-dependent mechanism. Antigenic peptides were also presented to the CD4+ T cell clones when derived from endogenously produced hexon protein. Together, these results show that cross-reactive HAdV-specific CD4+ T cells can control replication of HAdV in vitro and provide a rationale for the use of HAdV-specific T cells in adoptive immunotherapy protocols for control of life-threatening HAdV-infections in immunocompromised patients.

Viral respiratory tract infections in transplant patients: epidemiology, recognition and management

Viral respiratory tract infections (RTIs) are common causes of mild illness in immunocompetent children and adults, with occasional significant morbidity or mortality in the very young, very old or infirm. However, recipients of solid organ transplants (SOT) or haematopoietic stem cell transplants (HSCT) are at markedly increased risk for significant morbidity or mortality from these infections. The infections are generally acquired by transmission of large respiratory droplets and can be nosocomial in origin with many documented outbreaks on specialised transplant units. Typically, the infections begin as upper RTIs, with cough or rhinorrhoea predominating. Many will resolve at this stage, but more immunocompromised patients, typically closer in time to their SOT or HSCT, may develop progressive infection to lower RTI or pneumonia. The most common RTI pathogens are influenza viruses, parainfluenza viruses and respiratory syncytial viruses. Newer polymerase chain reaction-based diagnostic strategies are more sensitive than previous assays, and allow rapid and accurate diagnoses of these infections. These newer assays may also detect emerging pathogens of significance, one of which is human metapneumovirus. While diagnostic techniques have advanced significantly in the past decade, well established and effective specific treatments for these infections remain elusive. The epidemiology, clinical presentation, diagnosis and treatment of the common viral RTIs in SOT or HSCT recipients are reviewed, and recommendations presented based on a thorough review of recent literature.

Respiratory virus infections in children with cancer or HIV infection

Most studies focusing on respiratory infections in immunocompromised children have been addressed to bacterial etiology. However, respiratory virus infections in this population can also lead to severe disease. The objective of this study is to evaluate the clinical significance of respiratory virus infections in children with cancer or human immunodeficiency virus (HIV) infection. Retrospective study conducted in a teaching hospital in Madrid. Medical records from children <or=14 years diagnosed with cancer or with HIV infection were reviewed. We analyzed demographic characteristics, clinical syndromes associated with the infection, need for hospitalization, treatment prescribed, and outcome. Fifty-three respiratory viral infections were identified: 26 (20%) in 129 HIV-infected children and 27 (12%) in 218 children with cancer. Twenty (38%) of the respiratory infections were nosocomial. Causal viruses were: respiratory syncytial virus, 43%; influenza A, 26%; adenovirus, 13%; parainfluenza virus, 13%; and influenza B, 4%. Thirty-three children were hospitalized: 14 (54%) with HIV infection and 19 (70%) receiving anticancer chemotherapy. Pneumonia occurred in 11 (34%) of the 33 hospitalized children. Four (21%) of the 19 hospitalized children with cancer, but none of the HIV-infected children, were admitted to the Pediatric Intensive Care Unit (P=0.096). Two children with cancer died. Common respiratory virus infections in children with cancer or HIV infection have a relevant morbidity. The fact that 40% of these infections are hospital-acquired emphasizes the need for isolation and preventive measures.

Viral pneumonias other than cytomegalovirus in transplant recipients

Community-acquired respiratory viruses (CARVs) are frequent causes of upper and lower respiratory tract infections in transplant recipients. In most series, respiratory syncytial virus and parainfluenza are the most common CARVs, followed by influenza and adenovirus. Significant morbidity and mortality are associated with these infections, particularly when they progress to pneumonia or when they are associated with bacterial or fungal coinfections. Outcomes are also poor with adenovirus, frequently reflecting disseminated infection. Efforts to prevent morbidity and mortality from CARV infection should focus on prevention, because treatment options are limited with inconclusive data to support their efficacy.

Cell-mediated immune responses to influenza vaccination in healthy volunteers and allogeneic stem cell transplant recipients

Influenza is one of the most common respiratory diseases in humans. The response to vaccination is frequently poor in immunosuppressed individuals. The aim of the present study was to develop an enzyme-linked immunospot (ELISPOT) assay for measuring of the specific T-cell response to influenza vaccination. In all, 18 healthy subjects and six stem cell transplantation (SCT) patients tested before and 4 weeks after influenza vaccination were included in the present study. Peripheral blood lymphocytes were stimulated with four influenza peptides; three based on sequences from the hemagglutinin and one from the M1 protein. The ELISPOT assay and the measurement of intracellular IFN-gamma production were used to determine the cell-mediated responses after stimulation with the peptides. Influenza vaccination elicited strong cell-mediated immune responses in the healthy controls to all four peptides with 3.2-6.9-fold increases in the number of IFN-gamma producing spots/10(6) cells. By intracellular staining, it was suggested that CD4+ cells mediated the responses to the hemagglutinin peptides. In contrast, there was no increase in the number of IFN-gamma producing cells response after vaccination in the six SCT patients. In conclusion, our results suggest that the ELISPOT assay might be used as a complement to serology for monitoring of future influenza vaccine studies in SCT patients.

Prospective study of the incidence, clinical features, and outcome of symptomatic upper and lower respiratory tract infections by respiratory viruses in adult recipients of hematopoietic stem cell transplants for hematologic malignancies

Respiratory viruses (RVs) are known to be major causes of morbidity and mortality in recipients of hematopoietic stem cell transplants (HSCTs), but prospective long-term studies are lacking. We prospectively screened all adult HSCT recipients (172 allogeneic [alloHSCT] and 240 autologous [autoHSCT]) who underwent transplantation during a 4-year period (1999 to 2003) for the development of a first episode of symptomatic upper respiratory tract infections and/or lower respiratory tract infections (LRTI) by an RV. RVs studied were influenza A and B viruses (n=39), human respiratory syncytial virus (n=19), human adenoviruses (n=11), human parainfluenza viruses 1 to 3 (n=8), human enteroviruses (n=5), human rhinoviruses (n=3), and the recently discovered human metapneumoviruses (n=19). During the study, 51 and 32 cases of RV symptomatic infections were identified of alloHSCT and autoHSCT recipients (2-year incidence, 29% and 14%, respectively). Risk factors for progression of upper respiratory tract infection to LRTI included severe (<0.2x10(9)/L) and moderate (<0.2x10(9)/L) lymphocytopenia in alloHSCT (P=.02) and autoHSCT (P=.03). Death from LRTI was attributed to an RV in 8 alloHSCT recipients. Symptomatic RV had no effect on 2-year outcomes, with the possible exception of influenza A and B virus infections in autoHSCT: these were associated with nonrelapse mortality (P=.02). In conclusion, this prospective trial allows an estimation of the minimum incidence of a first RV infection in adult HSCT recipients and identifies risk factors for acquisition of an RV infection and progression to LRTI; this should aid in the design of future studies. In addition, human metapneumovirus should be added to the potentially serious causes of RV infections in HSCT.

[High resolution computed tomography findings in parainfluenza virus pneumonia after bone marrow transplantation: case report]

Nineteen year-old female patient, who underwent bone marrow transplantation because of chronic myelogenous leukemia, presented with dry cough and coriza sixty-seven days after the procedure. The chest radiograph was normal. The high resolution computed tomography showed a subsegmental air-space consolidation at the periphery of the left inferior lobe and areas of low attenuation at the superior and middle lung zones. The bronchoalveolar lavage demonstrated positive direct fluorescence antibody testing against parainfluenza virus. Treatment with aerolizated ribavirin was instituted during 10 days and the patient showed clinical-radiological improvement.

Molecular detection and quantitative analysis of the entire spectrum of human adenoviruses by a two-reaction real-time PCR assay

Adenoviruses (AdV) can cause life-threatening infections in immunosuppressed patients. Reliable diagnostic tests are therefore of paramount importance. Apparently, any of the six AdV species (A to F), currently comprising 51 different serotypes, can play a clinically important role in patients with impaired immune response. It is imperative therefore that diagnostic assays cover the entire spectrum of these viruses. We have sequenced presumably conserved regions of the adenoviral genome in all AdV serotypes. Based on the complete sequence information of the hexon gene, we were able to develop a two-reaction real-time PCR assay covering all human adenoviruses with equally high specificity and sensitivity. The detection systems were tested using reference strains for all 51 serotypes and >1,000 clinical samples derived from peripheral blood and stool specimens from pediatric patients after allogeneic stem cell transplantation. The two-reaction assay presented permits highly specific detection and quantification of adenoviral DNA of any serotype. From the perspective of routine clinical diagnosis, the assay represents an important improvement over existing approaches by providing a sensitive and economic technique for early detection and monitoring of adenoviral infections.

A prospective study comparing human metapneumovirus with other respiratory viruses in adults with hematologic malignancies and respiratory tract infections

Human metapneumovirus (hMPV) is a recently described paramyxovirus associated with upper and lower respiratory-tract infection (URI and LRI, respectively). We conducted a prospective study of URI and LRI in adults with hematologic malignancies during a 4-year period. We retrospectively tested samples by reverse-transcription polymerase chain reaction for hMPV and analyzed clinical data. Twenty-two (9%) of 251 episodes of respiratory infection tested positive for hMPV. Sixteen (73%) of the illnesses occurred in hematopoietic stem-cell transplant recipients. Nine patients with hMPV developed LRI; 3 of these patients died. hMPV is a common cause of respiratory infections in adults with hematologic malignancies, with associated morbidity and mortality.

Molecular genetic methods in the diagnosis of lower respiratory tract infections

Molecular diagnostic techniques, such as PCR, have become useful tools for the rapid etiological diagnosis of lower respiratory tract infections. Nucleic acid amplification tests (NAATs) have been evaluated for detecting most respiratory pathogens, and commercial assays are available for some pathogens. However, standardized protocols are needed before these assays are introduced into routine diagnostic use. For pneumonia, NAATs offer advantages over conventional tests for the detection of Mycoplasma pneumoniae, Legionella spp. and Chlamydia pneumoniae. For pneumococcal pneumonia in adults, PCR adds little to existing diagnostic tests, and is unable to distinguish pneumococcal colonization from infection when testing respiratory samples. Although less sensitive than culture-based methods, several commercial molecular diagnostic assays have been developed for tuberculosis and are useful rapid tests for selected patients. PCR can now be considered the rapid diagnostic test of choice for pertussis and some respiratory virus infections. Further work is required to better characterize the role of molecular diagnostic tests for diagnosing lower respiratory tract infections, and to develop standard assays that can be readily adopted by routine diagnostic laboratories.

Pneumonia pelo vírus influenza B pós-transplante de medula óssea: relato de caso com ênfase dos achados de tomografia computadorizada de alta resolução

Nine year-old male patient, who underwent bone marrow transplantation because of acute myelogenous leukemia, presented with fever and dry cough three days after the procedure. The chest radiograph demonstrated bilateral diffuse reticular infiltrate. The high resolution computed tomography showed peribronchovascular interstitial thickening, peripheral small centrilobular nodules and areas of ground-glass attenuation. The bronchoalveolar lavage demonstrated positive direct fluorescence antibody testing against influenza B virus. Treatment with aerolizated ribavirin was instituted during 10 days and the patient showed clinical-radiological improvement.

Respiratory Viruses and Severe Lower Respiratory Tract Complications in Hospitalized Patients

BACKGROUND

Acute respiratory viral infections are generally self-limited in healthy subjects but can lead to severe complications in immunocompromised hosts. We report the clinical impact of acute lower respiratory tract viral infections in hospitalized patients.

MATERIALS AND METHODS

Of 1,001 fiberoptic bronchoscopies performed during a period of 5 years, 33 BAL samples were positive for respiratory viruses by cell culture. The main diagnosis, length of hospitalization, response to initial treatment, and the mortality rate at 30 days were analyzed. Spirometry performed before and after infection was compared in lung transplant recipients.

RESULTS

The following respiratory viruses were identified in 33 cases: influenza A or B (n = 13), parainfluenza virus 1-3 (n = 7), rhinovirus (n = 5), respiratory syncytial virus (n = 4), and adenovirus (n = 4). All cases were immunocompromised patients who acquired new respiratory symptoms and/or radiologic abnormalities suggesting a pulmonary infection. Twenty-five patients (74%) did not respond to initial broad-spectrum antibiotics, and 11 patients (33%) required intensive care for respiratory failure. The overall mortality rate at 1 month was 24%. In patients with a sole viral pathogen identified in their BAL, the mortality rate was 39%. In lung transplant recipients (n = 10), the mean FEV(1) decreased from 2.2 to 1.9 L/s before and during the infection episode, respectively (p < 0.01); 3 months later, 60% of the patients had still not completely recovered to baseline values.

CONCLUSION

Respiratory viruses recovered in BAL samples of immunocompromised patients are associated with severe lower respiratory complications. In lung transplant recipients, we observed a persisting impairment of pulmonary function.

Applicability of a real-time quantitative PCR assay for diagnosis of respiratory syncytial virus infection in immunocompromised adults

Respiratory syncytial virus (RSV) accounts for the majority of respiratory virus infections, producing high mortality rates in immunocompromised patients with hematologic malignancies. The available methods for the rapid detection of RSV by antigen detection or PCR either lack sensitivity, require complex laboratory manipulation, or have not been evaluated in this patient population. To assess the applicability of a TaqMan-based real-time PCR technique for the detection of RSV A and B in immunocompromised adults, we developed a rapid, sensitive detection method that simultaneously detects RSV A and B and can be applied in routine diagnostics. The specificity of the assay was assessed using a panel of reference strains of other respiratory viruses and RSV. Electron microscopy-counted stocks of RSV A and B were used to develop a quantitative PCR format. Eleven copies of viral RNA could be detected for RSV A strain Long, and 14 copies could be detected for RSV B strain 9320, corresponding to 50% tissue culture infective doses of 0.86 and 0.34, respectively. The assay was evaluated on 411 combined nose and throat swabs derived from immunocompromised adults with or without signs of respiratory tract infection. The diagnostic efficacy of the TaqMan PCR determined on the clinical samples showed that this real-time PCR technique was substantially more sensitive than the combination of conventional viral culture and shell vial culture. None of the clinical specimens derived from patients without signs of respiratory illness were found to be positive for RSV by real-time TaqMan PCR.

Molecular monitoring of adenovirus in peripheral blood after allogeneic bone marrow transplantation permits early diagnosis of disseminated disease

Adenovirus (AdV) infection in the course of allogeneic stem cell transplantation (SCT) is associated with high transplant-related morbidity and mortality. Disseminated AdV disease is lethal in most instances. Early detection of AdV infection and identification of patients carrying a high risk of disseminated disease therefore remain a major challenge. In view of the large number of existing AdV types, we have established real-time polymerase chain reaction (PCR) assays permitting sensitive detection and quantification of all 51 currently known human AdV serotypes. In a series of 132 consecutive pediatric patients undergoing SCT, more than 5000 samples derived from peripheral blood (PB), stool, urine, and throat were screened for adenovirus infection by PCR during the posttransplantation period. Thirty-six patients (27%) tested positive by PCR, revealing AdV types of the subgenera A, B, C, D, and F. Except for enteritis in some patients with AdV positivity in stool, detection of the virus at sites other than PB was not associated with clinical signs of virus disease, and transplant-related mortality was not significantly different from AdV-negative patients. By contrast, 82% of patients who had detectable AdV in PB died from infectious complications (P <.001). Monitoring of PB specimens by real-time PCR permitted early diagnosis of invasive AdV infection in all instances. In patients who developed disseminated AdV disease, detection of the virus in PB preceded onset of clinical symptoms by a median of more than 3 weeks. The observation of AdV in peripheral blood may therefore serve as a basis for early initiation of preemptive antiviral treatment.