key: cord-0775413-xwd0tm1d
authors: Piñana, Jose Luis; Xhaard, Aliénor; Tridello, Gloria; Passweg, Jakob; Kozijn, Anne; Polverelli, Nicola; Heras, Inmaculada; Perez, Ariadna; Sanz, Jaime; Berghuis, Dagmar; Vázquez, Lourdes; Suárez-Lledó, María; Itäla-Remes, Maija; Ozcelik, Tulay; Iturrate Basarán, Isabel; Karakukcu, Musa; Al Zahrani, Mohsen; Choi, Goda; Cuesta Casas, Marián Angeles; Batlle Massana, Montserrat; Viviana, Amato; Blijlevens, Nicole; Ganser, Arnold; Kuskonmaz, Baris; Labussière-Wallet, Hélène; Shaw, Peter J; Arzu Yegin, Zeynep; González-Vicent, Marta; Rocha, Vanderson; Ferster, Alina; Knelange, Nina; Navarro, David; Mikulska, Malgorzata; de la Camara, Rafael; Styczynski, Jan
title: Seasonal human coronaviruses respiratory tract infection in recipients of allogeneic hematopoietic stem cell transplantation.
date: 2020-08-29
journal: J Infect Dis
DOI: 10.1093/infdis/jiaa553
sha: c4a25711f2b909dd5237d9fcd40b86a283983bb7
doc_id: 775413
cord_uid: xwd0tm1d

BACKGROUND: Little is known about characteristics of seasonal human coronavirus (HCoV) (NL63, 229E, OC43 and HKU1) after allogeneic stem cell transplantation (allo-HCT). PATIENTS AND METHODS: this is a collaborative Spanish and European bone marrow transplantation groups retrospective multicentre study, which included allo-HCT recipients (adults and children) with upper and/or lower respiratory tract disease (U/LRTD) caused by seasonal HCoV diagnosed through multiplex PCR assays from January 2012 to January 2019. RESULTS: We included 402 allo-HCT recipients who developed 449 HCoV U/LRTD episodes. Median age of recipients was 46 years (range 0.3-73.8 years). HCoV episodes were diagnosed at a median of 222 days after transplantation. The most common HCoV subtype was OC43 (n=170, 38%). LRTD involvement occurred in 121 episodes (27%). HCoV infection frequently required hospitalization (18%), oxygen administration (13%) and intensive care unit (ICU) admission (3%). Three-month overall mortality after HCoV detection was 7% in the whole cohort and 16% in those with LRTD. We identified 3 conditions associated with higher mortality in recipients with LRTD: absolute lymphocyte count <0.1 x10 (9)/mL [hazard ratio (HR), 10.8], corticosteroid (HR 4.68) and ICU admission (HR 8.22) (p<0.01). CONCLUSIONS: Seasonal HCoV after allo-HCT may involve the LRTD in many instances, leading to a significant morbidity.

The development of molecular technologies and the widespread use of multiplex PCR assays for community-acquired respiratory viruses (CARVs) screening allows epidemiologic and clinical characterization of seasonal human coronaviruses (HCoV) infections in immunocompromised patients 1, 2, 3 . Coronaviruses are a group of enveloped viruses with non-segmented, single-stranded, and positive-sense RNA genomes. Of the 4 genera of coronaviruses, Gammacoronavirus and Deltacoronavirus exclusively infect animals whereas most of the Alphacoronavirus and some of the Betacoronavirus are well recognized to infect humans 4 . Among the seven known HCoV subtypes that affect humans, HCoV-229E and HCoV-NL63 belong to Alphacoronavirus, whereas HCoV-OC43 and HCoV-HKU1 belong to lineage A, severe acute respiratory syndrome-human coronavirus (SARS-CoV) and novel coronavirus (SARS-CoV-2) to lineage B, and Middle East respiratory syndrome-HCoV (MERS-HCoV) to lineage C, both belonging to Betacoronavirus 5 . Priors and recent outbreaks of zoonotic HCoV infections such as SARS-CoV 6-8 , MERS-HCoV 9 and recently SARS-CoV-2 10, 11 , support the idea that coronavirus could be one of the most rapidly evolving viruses owing to its high genomic nucleotide substitution rates and recombination 12 . However, seasonal HCoV (HCoV-NL63, HCoV-229E, HCoV-OC43 and HCoV-HKU1) have circulated globally in the human population for decades and although they contribute to approximately one-third of common colds in humans, their severity seems not as devastating as the zoonotic coronavirus outbreaks with no fatalities in pediatric 13 or relatively low mortality rate (4%) in elderly chronic obstructive pulmonary disease (COPD) patients 14 .

Nevertheless, knowledge of the consequence of seasonal HCoV respiratory infection in highly immunocompromised patients, such as allogeneic stem cell transplantation (allo-HCT) recipients, remains poorly characterized to date.

CARVs epidemiology in allo-HCT recipients parallels the epidemiology in the general population 15 , although these respiratory infections are particularly threatening after allo-HCT [16] [17] [18] . Early studies showed that HCoVs were detected in lung tissues in transplant recipients developing severe A c c e p t e d M a n u s c r i p t 8 pneumonia [19] [20] [21] [22] . Compared to other CARVs, prior reports with a small number of cases suggest that HCoV upper and/or lower respiratory tract disease (U/LRTD) were quite frequent after allo-HSCT, representing 11% to 14% of all CARVs 1, 2, 3 . In contrast to previous observations, recent smaller studies have shown that HCoV could involve the LRT in many instances in allo-HCT recipients (14% to 33%) 1, 3 . Overall mortality of such cases ranged from 11% to 54% at 3 months after the HCoV detection which was similar to that seen in RSV, influenza and parainfluenza virus LRTD in allo-HCT recipients 1, 3, 23 .

In this large retrospective international multicenter cohort, we aimed to characterize epidemiological and clinical features, risk factors (RFs) and outcome of seasonal HCoV infections in a severe immunocompromised population such as allo-HCT recipients.

This is a retrospective collaborative multicenter cohort study between the Infectious Diseases Working Party (IDWP) of the European Society for Blood and Marrow Transplantation (EBMT) and the Infectious Complications Subcommittee (GRUCINI) of the Spanish Hematopoietic Stem Cell Transplantation and Cell Therapy Group (GETH), focused on allo-HCT recipients with U/LRTD symptoms caused by seasonal HCoV types (HCoV-NL63, HCoV-229E, HCoV-OC43 or HCoV-HKU1) which were detected by multiplex PCR panels. The EBMT is a scientific organization that collects data from associated centers that perform HSCT through a web-based registry called ProMISe in accordance with standards at every center for patient confidentiality and good clinical practice.

A c c e p t e d M a n u s c r i p t 9

The EBMT participating centers were requested to include all consecutive allo-HCT recipients (children and adults) with laboratory-documented seasonal HCoV respiratory infection during a period comprised from January 1 st 2012 to January 30 th 2019. All consecutive HCoV respiratory infection episodes per recipient that occurred from the day of conditioning regimen to the last follow-up during the aforementioned period were included. The inclusion of HCoV cases that were detected during conditioning but before stem cell infusion is justified by the potential negative impact of pre-transplant CARV detection 24 . The exclusion criterion was baseline disease relapse or progression before the HCoV detection.

During the study period, all allo-HCT procedures were registered in ProMISe by completing the essential medical data form. This form is mandatory for all centers belonging to the EBMT network.

Data that is more detailed was collected using a second transplant form that contained specific information regarding a description of respiratory symptoms, HCoV-related hospital admission, oxygen requirement and ICU admission. Variables such as immunosuppressant drugs, corticosteroids, the presence of signs or symptoms of acute or chronic graft-versus-host disease (GvHD), prior development of bronchiolitis obliterans syndrome (BOS) and variables for immunodeficiency scoring index (ISI) computation 25 (i.e. lymphocyte count, neutrophils count, myeloablative conditioning regimen, age, corticosteroids therapy and graft-versus-host disease) were requested at the time of CARV PCR screening.

URTD was defined as the combination of upper respiratory symptoms (rhinorrhea, sinusitis, otitis, or pharyngitis), identification of seasonal HCoVs by PCR assay and the absence of LRTD symptoms and/or any pulmonary infiltrates on chest X-ray or computed tomography (CT) scan of the lung. We classified LRTD as possible, probable or confirmed, as previously described 26 . There were no A c c e p t e d M a n u s c r i p t 10 probable episodes because bronchoscopies were not performed in patients without radiological proof of pulmonary involvement. We defined episodes as an URTD or LRTD according to ECIL-4 recommendations 27 . An infectious disease episode was considered to be resolved when complete remission of respiratory symptoms was observed. A further episode of a respiratory tract infectious disease required the presence of a symptom-free period of at least two consecutive weeks from the resolution of the previous episode and/or the isolation of a different subtype of HCoV in conjunction with the onset of new respiratory symptoms. Acute and chronic GvHD, including BOS were diagnosed according to standard criteria 28 .

A co-infection was defined as a significant co-pathogen detected in concurrent nasopharyngeal, bronchoalveolar lavage, or in a blood sample obtained during the course of HCoV infection.

CARV testing in respiratory samples were performed with different multiplex PCR platforms. Details regarding the CARV type's performance for each PCR test is provided in Table 1 . Briefly, 5 of 9 commercial multiplex PCR assays and other unspecified PCR platforms were able to detect and discriminate all four common HCoV subtypes, whereas one commercial PCR assay only detected three out of four HCoV (NL63, 229E, OC43), one in-house PCR assay only detected 2 HCoV (229E and OC43) and one commercial PCR assay only detected HCoV-229E subtype. A commercial multiplex PCR assay detected the four strains of HCoV but was not able to discriminate among them. Finally, an unknown PCR platform was able to detect all four HCoV without information on HCoV subtype and then HCoVs in these cases were classified as non-subtypable.

A c c e p t e d M a n u s c r i p t 11

The primary objective of the study was to describe epidemiological and clinical characteristics of U/LRTD in allo-HCT recipients with seasonal HCoV infection. We also analyzed differences in clinical manifestations among HCoV subtypes as well as RFs for HCoV-related hospital admission, oxygen requirement, LRTD involvement, and all-cause mortality by day 90 after HCoV detection, the later in recipients with LRTD. We selected day 90 as a cut-off for mortality analysis to capture HCoV-related late events since CARV shedding could be longer than 12 weeks in allo-HCT recipients 17 .

The main characteristics of patients were reported by descriptive statistics on the total of the available information, median and range were used for continuous variables, whilst absolute and percentage frequency were used for categorical variables. Differences between groups were tested using linear or logistic regression models, using the generalized estimating equation methods to take into account the dependence of observations, nested by patient. Variables with a p-value < 0.1 in the univariate model were included in the multivariate analysis. In recipients with LRTD, the survival analysis was performed by using the Cox regression model. A p-value <0.05 was considered statistically significant. All p-values were two-sided. All the analyses were performed using the statistical software SAS v. 9.4 (SAS Institute Inc., Cary, NC, USA).

Overall, we included 402 pediatric and adult allo-HCT recipients with a median age of 46 years Table 2 . The study population comprised a high-risk cohort, since 57% of the recipients were allografted from alternative donors [unrelated adult donor, cord blood units (CBU) or haplo-identical A c c e p t e d M a n u s c r i p t 12 family donors]. There were 364 allo-HCT recipients with one HCoV episode and 38 (9.5%) recipients with two or more HCoV episodes.

Median time from allo-HCT to first HCoV episode was 222 days (range -9 days to 20 years). Seven cases (1.5%) were diagnosed before stem cell infusion whereas most of cases occurred within the first year of stem cell infusion (n= 262, 58%). There were 434 episodes with only one HCoV subtype whereas in 15 episodes (3%) we observed two or more HCoV subtypes in the same respiratory sample. In this series the most common HCoV was OC43 (n= 170, 38%) followed by 229E (n= 97, 22%), NL63 (n= 64, 14%) and KHU1 (n=54, 12%). This order was maintained when we analyzed the HCoV subtypes diagnosed through multiplex PCR assays capable of detecting and differentiating all four HCoV strains (n= 306, 68%): OC43 (n=134, 43.5%) followed by 229E (n=64, 20.8%), and by NL63 (n=54, 17.5%) and HKU1 (n=54, 17.5%). There were 79 episodes (17.5%) with non-subtypable HCoVs.

Although HCoV circulated all year long, most of the episodes (n= 375, 83%) were diagnosed during cold months ( Figure 1A ). We did not observe significant differences in HCoV subtype distribution between countries and continents. However Table 3 .

A c c e p t e d M a n u s c r i p t 13

Clinical and laboratory differences according to URTD or LRTD involvement are summarized in Table   4 . Overall, 446 out of 449 HCoV episodes (99%) involved the URTD (328 of them, 73%, limited to URTD) whereas 121 (27%) had LRTD involvement (106 possible and 15 proven). A third of episodes (n=153, 35%) had fever at the time of HCoV detection leading to hospital admission in 80 cases (18%), oxygen requirement in 56 cases (13%) and ICU admission in 13 cases (3%). As expected, the group developing HCoV LRTD had significantly higher rates of severe immunosuppression-related factors. ISI variables (lymphopenia, active GVHD, corticosteroid therapy) as well as bacterial, fungal and other CARV co-infections were significantly over-represented in the HCoV LRTD group (p ≤ 0.05 for all comparisons). Characteristics of significant co-pathogens including CARV, bacterial and fungal agents are detailed in table 5. As expected, HCoV LRTD showed higher rates of fever, hospital admission, oxygen requirement and intensive care unit admission (p< 0.001 for all comparisons).

Logistic regression and Cox regression multivariate analyses of conditions associated with hospital admission, oxygen requirements, HCoV LRTD and all-cause day 90 mortality in those with LRTD involvement are shown in Table 6 . Finally, the conditions associated with increased mortality in recipients developing HCoV LRTD were ALC < 0.1 × 10 9 /L [hazard ratio (HR) 10 .82], corticosteroids therapy (HR 4.68) and ICU admission (HR 8.22) . Mortality of patients with LRTD increased according to the presence of these RFs. Those with none or 1 RF had a mortality rate of 11% compared to those with 2-3 RFs (57%) (p <0.0001).

We did not found differences in outcomes among pediatric (< 18 years) and adults (≥18 years). The rate of LRTD, hospital admission, oxygen support and overall mortality of pediatric recipients compared to adults were 31% vs 26% (p= 0.6), 7% vs 18% (p= 0.15), 18% vs 12% (p= 0.3) and 2% vs 7% (p= 0.3), respectively.

All-cause mortality rate at three months after HCoV detection was 7% (n= 31) for the entire group.

Mortality of recipients with HCoV limited to URTD was 3.5% (n= 11) whereas it was 16% (n= 20) (p <0.0001) in those with LRTD. According to the coronavirus genera, 3-month overall mortality was 3% in the Alphacoronavirus group vs 7% in the Betacoronavirus group (p= 0.28) in both U/LRD, whereas it was 3% vs 10% for those with LRTD, respectively (p= 0.25).

Fifteen recipients died by day 30 after HCoV diagnosis. Ten additional recipients died at day 60 and six more recipients died by day 90 after HCoV diagnosis. In total, 11 and 20 recipients with URTD or LRTD died, respectively. The numbers of death by day 30, day 60 and day 90 were 6, 3 and 1 for URTD and 9, 6 and 5 for LRTD. 

This study shows that HCoV episodes in the setting of allo-HCT predominate during cold months, with HCoV-OC43 (38%) being the most common HCoV subtype. The detection of seasonal HCoV was associated with considerable morbidity after allo-HCT and it was frequently accompanied by copathogens in the LRT leading to hospitalization, oxygen requirement and ICU admission in a not irrelevant proportion of cases. Three-month overall mortality after HCoV detection was 7% in the whole cohort and 16% in those with LRTD. We identified several RFs for different outcomes that could be of value for close clinical monitoring and/or risk-stratification for future clinical trials.

Our study confirms that seasonal HCoV predominate during cold months 29 also in allo-HCT recipients. In line with several reports in the general population 29-31 the most common seasonal HCoV in our series was OC43, belonging to betacoronavirus genus. Although we observed subtle differences over the years in HCoV subtypes' prevalence, it is noteworthy to mention that betacoronavirus genus (OC43 and HKU1) predominated from 2014 and onwards. This fact, along with the recent pandemic caused by another betacoronavirus (SARS-COV-2), suggests that differential characteristics of betacoronavirus genus may provide a biological advantage to survive Seasonal HCoV usually causes mild respiratory illnesses in the general population. Although prior studies and reviews suggested that seasonal HCoV may occasionally cause LRTDs after allo-HSCT 2,33 , our study showed that 27% of allo-HSCT recipients with HCoV may developed LRTD. This is in line with prior reports where LRTD occurred in 14% to 33% of cases 1,3 . Although we report a relevant rate of HCoV LRTD, attributing LRTD to HCoV is challenging due to the frequent presence of copathogens. In addition, it should be note that the only way to establish the true effect of HCoV in the lungs is through the demonstration of HCoV's antigens and/or RNA in lung tissues. The observation that 18% of HCoV cases required hospital admission, 13% oxygen support and 3% ICU admission, indicates that seasonal HCoV could be related with a severe course in these highly immunosuppressed patients. Although recipients with isolated URTD had a relatively low overall mortality rate at 3-months after HCoV detection (3.5%), those who developed pulmonary complications showed a significant higher mortality rate (16%). This observation was also true when we looked at day +30 mortality which could be a more accurate time point to evaluate direct effects of HCoV (1.8% vs 7.4%, p= 0.01, respectively). These facts support recent findings from a retrospective study where the detection of HCoV in the LRT was significantly related with higher rates of respiratory support and mortality in immunocompromised hosts, similar to that of established respiratory pathogens including respiratory syncytial virus, influenza virus and human parainfluenza virus 23 . Importantly, we did not observe significant differences in terms of severity and mortality among HCoV subtypes. We acknowledge that this study has some limitations, such as the retrospective nature of the analyses, the low proportion of BAL performed, the absence of lung tissues analyses to establish the real role of HCoV and the use of several different PCR methods differing in their analytical performance for detection and identification of HCoV subtypes. In spite of this, our study has strengths that merit consideration. We included a large multi-center cohort of HCoV cases with detailed clinical and laboratory data in the molecular testing era.

In conclusion, we provide insights of seasonal HCoV infections after allo-HCT in terms of epidemiology and clinical outcome. Our study supports that these infections can have moderate to severe direct and indirect consequences in a significant proportion of cases and that testing for seasonal HCoV should be included in the CARV screening test in the allo-HCT setting.

A c c e p t e d M a n u s c r i p t

The author(s) declare that they have no conflict of interests.

Financial support. This work has no source of funding. ¥ The sum of the episodes does not match the overall number of episodes (n = 449) since multiple CARVs were detected in the same respiratory sample in 15 (3%) CARV episodes. 90-days all-cause mortality after CARV co-viral infection was 10% (17 out of 165). Sixty-one co-virus infectious episodes occurred within the first 6 months after stem cell infusion and mortality was 15% (9 out of 61). Sixteen (10%) and 14 (24%) out of 164 and 59 patients with URTD and LRTD CARV co-viral infection died, respectively. Finally, 7 (37%) out of 19 patients with LRTD CARV co-viral infection died within the first 6 months after stem cell infusion.

M a n u s c r i p t 32 

Epidemiologic and Clinical Characteristics of Coronavirus and Bocavirus Respiratory Infections after Allogeneic Stem Cell Transplantation: A Prospective Single-Center Study

Human rhinovirus and coronavirus detection among allogeneic hematopoietic stem cell transplantation recipients

Incidence, significance, and persistence of human coronavirus infection in hematopoietic stem cell transplant recipients

Discovery of seven novel mammalian and avian coronaviruses in Deltacoronavirus supports bat coronaviruses as the gene source of Alphacoronavirus and Betacoronavirus and avian coronaviruses as the gene source of Gammacoronavirus and Deltacoronavirus

Severe acute respiratory syndrome-related coronavirus: the species and its viruses -a statement of the Coronavirus Study Group

Epidemiology and cause of severe acute respiratory syndrome (SARS) in Guangdong, People's Republic of China

A novel coronavirus associated with severe acute respiratory syndrome

Identification of a novel coronavirus in patients with severe acute respiratory syndrome

Isolation of a novel coronavirus from a man with pneumonia in Saudi Arabia

Clinical features of patients infected with 2019 novel coronavirus in Wuhan

Epidemiological and clinical characteristics of 99 cases of 2019 novel coronavirus pneumonia in Wuhan, China: a descriptive study

Origin and evolution of pathogenic coronaviruses

Characterization of human coronavirus OC43 and human coronavirus NL63 infections among hospitalized children <5 years of age

Human coronavirus and acute respiratory illness in older adults with chronic obstructive pulmonary disease

Clinical effectiveness of influenza vaccination after allogeneic hematopoietic stem cell transplantation: A cross-sectional prospective observational study

Management of respiratory viral infections in hematopoietic cell transplant recipients and patients with hematologic malignancies

Prolonged respiratory viral shedding in transplant patients

Respiratory syncytial virus in hematopoietic cell transplant recipients: factors determining progression to lower respiratory tract disease

Use of a novel virus detection assay to identify coronavirus HKU1 in the lungs of a hematopoietic stem cell transplant recipient with fatal pneumonia

Coronavirus pneumonia following autologous bone marrow transplantation for breast cancer

Coronavirus 229E-related pneumonia in immunocompromised patients

Fatal lower respiratory tract disease with human coronavirus NL63 in an adult haematopoietic cell transplant recipient

Clinical Significance of Human Coronavirus in Bronchoalveolar Lavage Samples From Hematopoietic Cell Transplant Recipients and Patients With Hematologic Malignancies

Clinical outcomes associated with respiratory virus detection before allogeneic hematopoietic stem cell transplant

Immunodeficiency scoring index to predict poor outcomes in hematopoietic cell transplant recipients with RSV infections

Parainfluenza virus lower respiratory tract disease after hematopoietic cell transplant: viral detection in the lung predicts outcome

ECIL-4): guidelines for diagnosis and treatment of human respiratory syncytial virus, parainfluenza virus, metapneumovirus, rhinovirus, and coronavirus

National Institutes of Health Consensus Development Project on Criteria for Clinical Trials in Chronic Graftversus-Host Disease: I. The 2014 Diagnosis and Staging Working Group Report

Coronavirus occurrence and transmission over 8 years in the HIVE cohort of households in

Molecular characterization of human coronaviruses and their circulation dynamics in Kenya

The dominance of human coronavirus OC43 and NL63 infections in infants

The clinical benefit of instituting a prospective clinical community-acquired respiratory virus surveillance program in allogeneic hematopoietic stem cell transplantation

The clinical impact of coronavirus infection in patients with hematologic malignancies and hematopoietic stem cell transplant recipients

Community-acquired respiratory viruses in transplant patients: diversity, impact, unmet clinical needs

Respiratory syncytial virus infection in patients with hematological diseases: single-center study and review of the literature

Assessment of immunodeficiency scoring index performance in enterovirus/rhinovirus respiratory infection after allogeneic hematopoietic stem cell transplantation

The effect of timing on community acquired respiratory virus infection mortality during the first year after allogeneic hematopoietic stem

URTD, upper respiratory tract disease; LRTD, lower respiratory tract disease; EvRh, Enterovirus/rhinovirus; ADV, adenovirus; RSV, respiratory syncytial virus; HMPV, human metapneumovirus

HiV, human influenza virus

A c c e p t e d M a n u s c r i p t 20 A c c e p t e d M a n u s c r i p t 27 † Unknown PCR platforms: Outsourcing diagnostic services to independent institutes rendered the PCR platform used to detect HCoV unidentifiable. Depending on the degree of detail from the virology reports, unknown PCR platforms were distinguished according to HCoV subtype identification. Unknown PCR platforms were confirmed to detect the four conventional HCoV subtypes (NL63, OC43, HKU1, 229E) but not MERS or SARS. ‡ Total of 31 participating transplant centers: some transplant centers reported use of different PCR panels over the course of the study.Abbreviations: HCoV non-subtypable, human coronavirus (without subtyping); HMPV, human metapneumovirus; HPiV, human parainfluenza virus; RSV, respiratory syncytial virus; EvRh, enterovirus/rhinovirus; HBoV, human bocavirus; ADV, adenovirus; D, detectable by the PCR platform; N, not detectable by the PCR platform; I, detectable but indistinguishable from other HCoV subtypes by the PCR platform; U, unknown whether PCR platform is able to distinguish between HCoV subtypes.A c c e p t e d M a n u s c r i p t 28 *Variables included in univariate analyses include: type of donor, recipient age, donor/receptor human leucocyte antigen (HLA) mismatch, conditioning regimen-based antithymocytic globulin, GvHD prophylaxis, absolute neutrophile count (ANC) < 0.5 × 109/L, ALC <0.2 × 10 9 /L, ALC <0.1 × 10 9 /L, immunossupressant drugs at the time of HCoV detection, periengraftment period, allo-HCT <100 days, allo-HCT <180 days, allo-HCT <2 years, HCoV subtypes (OC43, 229E, NL63, HKU1 and non-subtypable), corticosteroids therapy >30 mg/day at the time of HCoV detection, oxygen support, mono vs coinfections (respiratory virus, bacteria and fungus), seasons (spring, summer, autumn, winter), prior bronchiolitis obliterans syndrome, immunoglobulin G levels <400 mg/dl and immunodeficiency score index (ISI).A c c e p t e d M a n u s c r i p t 38 Figure 1A A c c e p t e d M a n u s c r i p t 39 Figure 1B