High frequency of human bocavirus 1 DNA in infants and adults with lower acute respiratory infection

B cell immune response to human bocaviruses

BACKGROUND

Human bocaviruses (HBoVs) have been demonstrated in respiratory and gastrointestinal infections; however, the immune response to them has not been studied in detail. In this study, we investigated the B cell immune responses to HBoV1 and HBoV2, representing two different species of bocaviruses in humans.

METHODS

We analyzed the effects of stimulations with HBoV1 and 2 virus-like particles (VLPs) and of co-stimulation with HBoV1-rhinovirus (RV) on cells of the immune system by flow cytometry, transcriptomics, and luminometric immune assays.

RESULTS

Human B cells, and particularly B regulatory cells (Breg cells), showed an increased immune response to HBoV1-VLPs stimulation. These immune responses were also supported by increased IL-1RA and PDL1 expressions in IL-10+ B cells from peripheral blood mononuclear cells (PBMCs) stimulated with HBoV1-VLPs. In addition, increased levels of IL-10 and IL-1RA were determined in the supernatants of PBMCs following HBoV1-VLPs stimulation. HBoV1-VLPs and RV co-stimulation increased the IL-10+ B cell population. Transcriptome analysis by next-generation RNA sequencing showed an increased expression of IL-10 signalling and Breg cell markers in PBMCs stimulated with HBoV1-VLPs. Furthermore, TGF-β and chemoattractants MIP-1α, MIP-1β and IP10 protein levels were high in the supernatants of PBMCs stimulated with HBoV1-VLPs.

CONCLUSIONS

The findings demonstrate that in Breg cells, IL-10 signalling pathways, and anti-inflammatory activity are induced by HBoV1, which can explain the often mild nature of the disease. In addition, the immune regulatory response induced by HBoV1-VLPs may indicate a potential immunomodulatory role of HBoV1 on the immune system and may represent an immune regulatory strategy.

Demographic and clinical characteristics of human bocavirus-1 infection in patients with acute respiratory tract infections during the COVID-19 pandemic in the Central Province of Sri Lanka

BACKGROUND

Human bocavirus-1 (hBoV-1) was first detected in respiratory specimens in 2005. Due to high co-infection rates and prolonged shedding of the virus, the pathogenic role of hBoV-1 as a primary causative agent of respiratory infections is still under discussion. This study aimed to determine the prevalence of hBoV-1 infection in patients with acute respiratory tract infections (ARTIs) during the COVID-19 pandemic in the Central Province of Sri Lanka.

METHODS

A total of 1021 patients (Age 12 days to ≤ 85 years) with ARTI symptoms including fever, cough, cold, sore throat and shortness of breath within first 7 days of the illness were included. The study was carried out at the National Hospital, Kandy, Sri Lanka from January 2021 to October 2022. Respiratory specimens were tested to detect 23 pathogens including hBoV-1 using a real time PCR. Prevalence of hBoV-1 co-infections with other respiratory pathogens and distribution of hBoV-1 infection among different age groups were determined. Moreover, clinical and demographic characteristics of hBoV-1 mono-infection associated ARTI were compared with that of the hBoV-1 co-infections.

RESULTS

Respiratory infections were detected in 51.5% (526/1021) of the patients and of these 82.5% were mono- and 17.1% were co-infections. hBoV-1 was detected in 66 patients and this was the most prevalent respiratory virus associated with 40% co-infections. Of the 66 hBoV-1 positive patients, 36 had co-infections and of these 33 had dual and 3 had triple infections. Most of the hBoV-1 co-infections were identified in children aged 2-<5 years. hBoV-1 co-infections were most frequently detected with respiratory syncytial virus (RSV) and Rhino/ Entero viruses (Rh/EnV). No differences were observed in age, gender and clinical presentations in those with hBoV-1 mono- compared to co-infections. Intensive care admissions were less among hBoV-1 mono-infected than hBoV-1 co-infected patients.

CONCLUSION

This study shows a prevalence of 12.5% for hBoV-1 infections in patients with ARTI. RSV and Rh/EnV were the most common co-infecting pathogens with hBoV-1. Clinical features of hBoV-1 mono-infections were not different to that of the hBoV-1 co-infections. Interactions between hBoV-1 and other respiratory pathogens need investigation to identify the role of hBoV-1 in clinical severity of co-infections.

HBoV-1: virus structure, genomic features, life cycle, pathogenesis, epidemiology, diagnosis and clinical manifestations

The single-stranded DNA virus known as human bocavirus 1 (HBoV-1) is an icosahedral, linear member of the Parvoviridae family. In 2005, it was discovered in nasopharyngeal samples taken from kids who had respiratory tract illnesses. The HBoV genome is 4.7-5.7 kb in total length. The HBoV genome comprises three open-reading frames (ORF1, ORF2, and ORF3) that express structural proteins (VP1, VP2, and VP3), viral non-coding RNA, and non-structural proteins (NS1, NS1-70, NS2, NS3, and NP1) (BocaSR). The NS1 and NP1 are crucial for viral DNA replication and are substantially conserved proteins. Replication of the HBoV-1 genome in non-dividing, polarized airway epithelial cells. In vitro, HBoV-1 infects human airway epithelial cells that are strongly differentiated or polarized. Young children who have HBoV-1 are at risk for developing a wide range of respiratory illnesses, such as the common cold, acute otitis media, pneumonia, and bronchiolitis. The most common clinical symptoms are wheezing, coughing, dyspnea, and rhinorrhea. After infection, HBoV-1 DNA can continue to be present in airway secretions for months. The prevalence of coinfections is considerable, and the clinical symptoms can be more severe than those linked to mono-infections. HBoV-1 is frequently detected in combination with other pathogens in various reports. The fecal-oral and respiratory pathways are more likely to be used for HBoV-1 transmission. HBoV-1 is endemic; it tends to peak in the winter and spring. This Review summarizes the knowledge on HBoV-1.

Diagnosis and clinical significance of Human bocavirus 1 in children hospitalized for lower acute respiratory infection: molecular detection in respiratory secretions and serum

Introduction. Human bocavirus 1 (HBoV1) infection occurs with viral genome presence in respiratory secretions (RS) and serum, and therefore both samples can be used for diagnosis.

Gap statement. The diagnostic sensitivity of HBoV1 DNA detection in serum and the duration of DNAaemia in severe clinical cases have not been elucidated.

Aim. To determine HBoV1 DNA in serum and RS of paediatric patients hospitalized for lower acute respiratory infection (LARI) and to analyse the clinical–epidemiological features of positive cases.

Methodology. This was a prospective, transverse study. Physicians selected the clinical situations and obtained paired clinical samples (RS and serum) that were tested by PCR/qPCR for HBoV1. Positive cases were analysed considering time of specimen collection, co-detection, clinical manifestations and viral load; statistical significant level was set at α=0.05.

Results. HBoV1 was detected in 98 of 402 cases included (24 %); 18/98 (18 %) patients had the virus detectable in serum and 91/98 (93 %) in RS (P<0.001). Positivity rates were not significantly different in patients with RS and serum collected within or beyond 24 h of admission. Single HBoV1 infection was identified in 39/98 patients (40 %), three patients had HBoV1 in both clinical samples (3/39, 8 %) and 32 (32/39, 82 %) only in RS, 22 of them (69 %) with both clinical samples within 24 h of admission. Cough (P=0.001) and rhinitis (P=0.003) were significantly frequent among them and most patients were diagnosed with bronchiolitis (22/39, 56 %) and pneumonia (9/39, 23 %), which was more frequent compared to cases with co-infection (P=0.04). No significant differences were identified among patients with high, medium or low viral load of HBoV1 regarding rate of positivity in both clinical samples, the time of collection of RS and serum, co-detection, first episode of LARI, clinical manifestations, comorbidity or requirement for assisted ventilation. Intensive care unit (ICU) patients had a significantly higher frequency of detection (P<0.001) and co-detection (P=0.001) compared to patients on standard care.

Conclusions. HBoV1 is prevalent among infant patients hospitalized for LARI and including it in the standard testing can add to the aetiological diagnosis in these cases, especially for patients admitted to the ICU. HBoV1 detection in serum did not contribute significantly to the diagnosis as compared to detection in respiratory secretions.

Human Bocavirus infection among children with respiratory tract infection in Ibadan, Nigeria

Background. Human Bocavirus (HBoV), which is an ssDNA virus of the family Parvoviridae, is responsible for 21.5 % of childhood respiratory tract infections (RTIs) annually. Among the four genotypes currently known, HBoV-1 has been associated with acute RTI. Although there have been studies on HBoV in some countries, there is limited information on this virus in sub-Saharan Africa where there is the highest burden of RTI. This study aimed to characterize the circulating strains of HBoV in Ibadan, Nigeria. Methods. Nasopharyngeal and oropharyngeal swab samples were collected from 333 children ≤5 years old presenting with RTI attending hospitals in Ibadan, whose parents assented, from 2014 to 2015. Twenty-three HBoV isolates were sequenced after a nested PCR and phylogenetic analysis was carried out using mega 6 software.

Results

A total of 27 children tested positive for the HBoV-1 genotype by PCR and 23 of the 27 isolates were successfully sequenced. The 23 HBoV-1 isolates from this study have been assigned GenBank accession numbers KY701984-KY702006. Phylogram analysis indicated that the isolates belong to the same clades. Six isolates aligned closely to the reference strains ST1 and ST2, while 17 isolates showed a high level of divergence to the reference isolates.

Conclusion

This study highlights the contribution of HBoV to RTIs in Nigeria and that HBoV-1 strains are associated with the infection.

Etiology of diarrheal disease among children under 5 years in Egypt: a high incidence of human bocavirus

BACKGROUND

Human bocavirus (HBoV) is globally distributed and associated with respiratory and enteric infections. Limited data are available about the incidence of HBoV in Egyptian children. We aimed to investigate the association of HBoV genotypes in children with diarrheal disease and also to determine the possibility of HBoV co-infections with other human enteric pathogens.

METHODS

A total of 102 stool samples were collected from children under five years old with diarrhea. Samples were analyzed for the presence of HBoV by real-time PCR. HBoV positive samples were tested for adenovirus (AdV), rotavirus (RoV), parasitic helminths, and enteric protozoa.

RESULTS

HBoV was detected in 58% of examined cases. HBoV-3 was the most prevalent genotype observed (44%; 45 of 102), followed by HBoV-2/4 (33%; 34 of 102) and HBoV-1 (30%; 31 of 102). Although the incidence of HBoV was higher in males (66.6%; 34 of 51) than females (49%; 25 of 51), the analysis showed no significant difference for HBoV between genders. The average HBoV concentrations were 5.3 × 10⁴ GC/g in males and 1.03 × 10⁵ GC/g in females. Among the HBoV-positive samples, the single infection of HBoV was 52.5% (31/59), while the co-infections with multiple viruses were found in 1.7% (1/59) for HBoV and AdV, 33.9% (20/59) for HBoV and RoV, and 11.9% (7/59) for HBoV, and RoV and AdV. No co-infection with parasitic helminths or enteric protozoa was found.

CONCLUSIONS

The single infection of HBoV in some children suffering from acute gastroenteritis indicated that HBoV could be the main etiologic agent of the disease. The study highlights the high incidence of HBoVs genotypes with remarkable multiple co-infections in the pre-school children in Egypt.

Human bocavirus genotypes 1, 2, and 3 circulating in pediatric patients with acute gastroenteritis in Chiang Mai, Thailand, 2012-2018

BACKGROUND

Global distribution of human bocavirus (HBoV) has been known to associate with viral gastroenteritis in pediatric population. This study was conducted in Chiang Mai, Thailand from 2012 to 2018 to investigate epidemiology and genotype distribution of HBoV in pediatric patients less than 5 years old hospitalized with diarrhea.

METHODS

A total of 2727 fecal specimens were investigated for the presence of HBoV using nested-PCR targeting partial VP1 capsid region. The detected HBoV strains were further characterized by nucleotide sequencing and phylogenetic analysis.

RESULTS

Detection rate of HBoV infection in pediatric patients with acute diarrhea was 5.2%. Three genotypes of HBoV were detected with the most predominance of HBoV1 (50.4%), followed by HBoV2 (42.5%), and HBoV3 (7.1%). The majority of HBoV positive cases were children of 1 to <2 years old (31.9%) with high detection rate of HBoV1 and HBoV2. HBoV infection occurred all year-round. Phylogenetic analysis revealed that majority of HBoV1 displayed the genetic relationship with HBoV1 strains reported previously from Asia whereas only a few were related to the strains from Europe, South America, and Middle East. The HBoV2 and HBoV3 were also mainly closely related to the strains reported from Asia and a few from South America and North Africa.

CONCLUSIONS

This study highlights distribution of HBoV genotypes circulating in pediatric patients with acute gastroenteritis in Chiang Mai, Thailand. Overall, three genotypes of HBoV were detected with equally high prevalence of HBoV1 and HBoV2 whereas HBoV3 was detected with much lower prevalence.

Human Bocavirus infection and respiratory tract disease identified in a UK patient cohort

•

Human Bocavirus 1 (HBoV1) was commonly detected in a survey of circa 13,000 UK respiratory samples between 2015 and 2019.

•

Co-infection with other viruses was observed in approximately three quarters of samples.

•

However, mono-infection was also prevalent, and associated with clinically relevant disease.

•

Intensive care was required in 31% of HBoV1 mono-infections and ventilation in 17%.

•

Fatal multi-organ failure was observed in an apparently HBoV1 mono-infected and otherwise healthy child.

Background

Since its first isolation in 2005, Human Bocavirus (HBoV) has been repeatedly associated with acute respiratory tract infections, although its role in pathogenicity remains unclear due to high co-infection rates.

Objectives

To assess HBoV prevalence and associated disease in a cohort of respiratory patients in the East Midlands, UK between 2015 and 2019.

Study design

We initially investigated the undiagnosed burden of HBoV in a retrospective paediatric cohort sampled between 2015 and 2017 using an in-house PCR assay. HBoV was subsequently incorporated into the standard respiratory diagnostic pathway and we audited a calendar year of HBoV positive results between 2018 and 2019.

Results

Our retrospective PCR screening of previously routine diagnostic-negative samples from juvenile patients identified a 9% (n = 30) prevalence of HBoV type 1. These apparent HBoV1 mono-infections were frequently associated with respiratory tract symptoms, often severe requiring ventilation, oxygen and steroid intervention with 31% (n = 9) of individuals requiring intensive care. When HBoV screening was subsequently adopted into the routine respiratory diagnostic pathway, year-round infections were observed in both children and adults peaking in February. 185 of 9098 (2.03%) individuals were found to be HBoV positive with children aged 12–24 months the principally infected group. However, HBoV infection was also observed in patients aged over 60, predominantly as a mono-infection. 23% of the 185 unique patients were HBoV monoinfected and persistent low-level DNA positivity was observed in 15 individuals up to 6-months after initial presentation.

Conclusion

HBoV1 is a prevalent respiratory infection in the UK capable of causing serious monoinfections.

Human bocavirus 1 infection of CACO-2 cell line cultures

Human bocavirus 1 (HBoV1) is a parvovirus associated with pneumonia in infants. It has been detected in different tissues, including colorectal tumors. In this study, we investigated whether Caco-2 cell line, derived from human colon cancer, can be utilized as a model for HBoV1 replication. We demonstrate HBoV1 replication in Caco-2 cultures supplemented with DEAE-dextran after inoculation with respiratory material from infected patients presenting with acute respiratory infection. A viral cycle of rapid development is displayed. However, in spite of HBoV1 DNA 4-fold increment in the supernatants and monolayers by day 1, evidencing that the system allows the virus genome replication after the entry occurred, infectious progeny particles were not produced. These results are consistent with an infection that is limited to a single growth cycle, which can be associated to mutations in the NS1 and VP1/VP2 regions of HBoV1 genome. Further research will contribute to fully elucidate these observations.

•

HBoV1 replicates within 24 h in standard and differentiated Caco-2 cells.

•

DNA is detected in attached cell and supernatant medium.

•

Immunofluorescence tests evidences HBoV1 infection.

•

DNA replication occurred but infectious progeny particles were not produced.

•

The viral genome presents deleterious mutations at NS1 and VP1/VP2 regions.

Human Bocavirus Type-1 Capsid Facilitates the Transduction of Ferret Airways by Adeno-Associated Virus Genomes

Human bocavirus type-1 (HBoV1) has a high tropism for the apical membrane of human airway epithelia. The packaging of a recombinant adeno-associated virus 2 (rAAV2) genome into HBoV1 capsid produces a chimeric vector (rAAV2/HBoV1) that also efficiently transduces human airway epithelia. As such, this vector is attractive for use in gene therapies to treat lung diseases such as cystic fibrosis. However, preclinical development of rAAV2/HBoV1 vectors has been hindered by the fact that humans are the only known host for HBoV1 infection. This study reports that rAAV2/HBoV1 vector is capable of efficiently transducing the lungs of both newborn (3- to 7-day-old) and juvenile (29-day-old) ferrets, predominantly in the distal airways. Analyses of in vivo, ex vivo, and in vitro models of the ferret proximal airway demonstrate that infection of this particular region is less effective than it is in humans. Studies of vector binding and endocytosis in polarized ferret proximal airway epithelial cultures revealed that a lack of effective vector endocytosis is the main cause of inefficient transduction in vitro. While transgene expression declined proportionally with growth of the ferrets following infection at 7 days of age, reinfection of ferrets with rAAV2/HBoV1 at 29 days gave rise to approximately 5-fold higher levels of transduction than observed in naive infected 29-day-old animals. The findings presented here lay the foundation for clinical development of HBoV1 capsid-based vectors for lung gene therapy in cystic fibrosis using ferret models.

Viral and atypical bacterial aetiologies of infection in hospitalised patients admitted with clinical suspicion of influenza in Thailand, Vietnam and Indonesia

Background

Influenza constitutes a leading cause of morbidity and mortality worldwide. There is limited information about the aetiology of infection presenting clinically as influenza in hospitalised adults and children in South-East Asia. Such data are important for future management of respiratory infections.

Objectives

To describe the aetiology of infection presenting clinically as influenza in those hospitalised in South-East Asia.

Methods

Respiratory specimens archived from July 2008 to June 2009 from patients hospitalised with suspected influenza from Indonesia, Thailand and Vietnam were tested for respiratory viruses and atypical bacteria by polymerase chain reaction.

Results

A total of 1222 patients’ samples were tested. Of 1222, 776 patients (63·5%) were under the age of 5. Viruses detected included rhinoviruses in 229 of 1222 patients (18·7%), bocaviruses in 200 (16·4%), respiratory syncytial viruses in 144 (11·8%), parainfluenza viruses in 140 (11·5%; PIV1: 32; PIV2: 12; PIV3: 71; PIV4: 25), adenovirus in 102 (8·4%), influenza viruses in 93 (7·6%; influenza A: 77; influenza B: 16) and coronaviruses in 23 (1·8%; OC43: 14; E229: 9). Bacterial pathogens were Mycoplasma pneumoniae (n = 33, 2·7%), Chlamydophila psittaci (n = 2), C. pneumoniae (n = 1), Bordetella pertussis (n = 1) and Legionella pneumophila (n = 2). Overall, in-hospital case fatality rate was 29 of 1222 (2·4%).

Conclusion

Respiratory viruses were the most commonly detected pathogens in patients hospitalised with a clinical suspicion of influenza. Rhinovirus was the most frequently detected virus, and M. pneumoniae, the most common atypical bacterium. The low number of detected influenza viruses demonstrates a low benefit for empirical oseltamivir therapy, unless during an influenza outbreak.

Acute human bocavirus infection in MDS patient, Cologne, Germany

•

A clinical case of persisting and reactivated HBoV infection is described.

•

HBoV can be detected in iliac crest in MDS patients.

•

The current episode appears to be a reactivation of the HBoV-1 strain that was detected 5 years ago in a colorectal biopsy of the patient.

Comorbidity and high viral load linked to clinical presentation of respiratory human bocavirus infection

Human bocavirus (HBoV) is a new parvovirus associated with acute respiratory tract infection (ARTI). In order to evaluate HBoV significance as an agent of acute respiratory disease, we screened 1,135 respiratory samples from children and adults with and without symptoms during two complete calendar years. HBoV1 prevalence in patients with ARTI was 6.33 % in 2011 and 11.64 % in 2012, including neonatal and adult patients. HBoV1 was also detected in 3.77 % of asymptomatic individuals. The co-detection rate was 78.1 %. Among children, 87 % were clinically diagnosed with lower respiratory infection (no significant differences between patients with and without coinfection), and 31 % exhibited comorbidities. Pediatric patients with comorbidities were significantly older than patients without comorbidities. Patients with ARTI had either high or low viral load, while controls had only low viral load, but there were no clinical differences between patients with high or low viral load. In conclusion, we present evidence of the pathogenic potential of HBoV1 in young children with ARTI. Since patients with HBoV1-single infection are not significantly different from those with coinfection with respect to clinical features, the virus can be as pathogenic by itself as other respiratory agents are. Furthermore, an association between high HBoV1 load and disease could not be demonstrated in this study, but all asymptomatic individuals had low viral loads. Also, children with comorbidities are susceptible to HBoV1 infection at older ages than previously healthy children. Thus, the clinical presentation of infection may occur depending on both viral load and the particular interaction between the HBoV1 and the host.

Single detection of human bocavirus 1 with a high viral load in severe respiratory tract infections in previously healthy children

BACKGROUND

Human bocavirus is a newly discovered parvovirus. Multiple studies have confirmed the presence of human bocavirus1 (HBoV1) in respiratory tract samples of children. The viral load, presentation of single detection and its role as a causative agent of severe respiratory tract infections have not been thoroughly elucidated.

METHODS

We investigated the presence of HBoV1 by quantitative polymerase chain reaction (PCR) of nasopharyngeal aspirate specimens from 1229 children hospitalized for respiratory tract infections. The samples were analyzed for 15 respiratory viruses by PCR and 7 respiratory viruses by viral culture.

RESULTS

At least one virus was detected in 652 (53.1%) of 1229 children, and two or more viruses were detected in 266 (21.6%) children. HBoV1 was detected in 127 children (10.3%), in which 66/127 (52%) of the cases were the only HBoV1 virus detected. Seasonal variation was observed with a high HBoV1 infection rate in summer. A cutoff value of 107 copies/mL was used to distinguish high and low HBoV1 viral loads in the nasopharyngeal aspirates. High viral loads of HBoV1 were noted predominantly in the absence of other viral agents (28/39, 71.8%) whereas there was primarily co-detection in cases of low HBoV1 viral loads (50/88, 56.8%). There were no differences in the clinical symptoms and severity between HBoV1 single detection and co-detection. In cases of HBoV1 single detection, the high viral load group was more prevalent among children with dyspnea and wheezing than was the low viral load group (42.9% vs. 23.7%, P = 0.036; 60.7% vs. 31.6%, P = 0.018). In clinical severity, a significant difference was recorded (25.0% vs. 5.3%, P = 0.003) between high viral load and low viral load groups. Of the HBoV1 positive patients associated with severe respiratory tract infections, 10/18 (55.6%) patients belonged to the HBoV1 high viral load group, and 7/10 (70%) patients had cases of HBoV1 single detection.

CONCLUSIONS

HBoV1 at a high viral load is not frequently found in co-detection with other respiratory viruses, and a single detection with a high viral load could be an etiological agent of severe respiratory tract infections.

Molecular detection of human metapneumovirus and human bocavirus on oropharyngeal swabs collected from young children with acute respiratory tract infections from rural and peri-urban communities in South India

Background

Acute respiratory tract infections (ARTIs) are one of the major causes of morbidity and mortality among young children in developing countries. Information on the incidence of human metapneumovirus (hMPV) and human bocavirus (HBoV) infections in developing countries, especially among rural children, is very limited.

Objectives

This study was conducted to identify whether these viruses were associated with ARTI among children ≤5 years of age in rural and peri-urban populations in South India.

Methods

The study was cross-sectional with prospective sample collection. Oropharyngeal swabs were collected from children ≤5 years of age presenting with ARTI. None of the children in this study were known to have any immunosuppressive conditions. The two viruses, hMPV and HBoV, were identified using semi-nested polymerase chain reaction (PCR) assays and one-step PCR assays, respectively. The lower limits of detection of hMPV and HBoV were 6.69 × 10⁵ plasmid copies and 5.77 × 10³ plasmid copies, respectively, per 5 μL PCR reaction input.

Results

The frequency of hMPV infection in children was higher than that of HBoV infection. The different frequencies of hMPV in patients in various age groups with upper and lower respiratory tract infections were compared, and the variance was found to be insignificant. In the 38 children who were hMPV positive, the majority (73.7 %) were from rural communities. The overall hMPV-positive rate was higher in the rural population than in the peri-urban population, but the difference was statistically insignificant. The youngest age at which hMPV-positive status was recorded was 5 months.

Conclusion

This study demonstrated that hMPV was associated with a significant number (i.e. >10 %) of ARTIs in children in South India, whereas a relatively smaller number of HBoV infections was observed.

Human bocavirus: lessons learned to date

Human bocavirus (HBoV) was identified as the second human parvovirus with pathogenic potential in 2005 in respiratory samples from children suffering from viral respiratory infections of unknown etiology. Since its first description, a large number of clinical studies have been performed that address the clinical significance of HBoV detection and the molecular biology of the virus. This review summarizes the most important steps taken in HBoV research to date and addresses open questions that need to be answered in the future to provide a better understanding of the role of a virus that is difficult to grow in cell culture and is suspected to be a pathogen, although it has not yet fulfilled Koch’s postulates.