Human parainfluenza virus types 1-4 in hospitalized children with acute lower respiratory infections in China

Molecular Epidemiology of Human Parainfluenza Virus Type 3 in Children With Acute Respiratory Tract Infection in Hangzhou

BACKGROUND

Since the outbreak of COVID-19, China has undertaken a variety of preventative and control measures, effectively reducing the incidence of numerous infectious diseases among the pediatric population in Hangzhou. We aim to investigate the genetic and epidemiological characteristics of Human parainfluenza virus-3 (HPIV-3) in pediatric patients during this period.

METHODS

A total of 1442 pharyngeal swab samples were collected from outpatients and inpatients with a diagnosis of acute respiratory tract infections (ARTIs) from November 2020 to March 2021. HPIV-3 was detected by quantitative real time polymerase chain reaction (qRT-PCR). The L gene of HPIV-3 positive samples was amplified and sequenced.

RESULTS

Among 1442 children with ARTI, the positive rate of HPIV-3 was 7.07% (102/1442). The positive detection rate was the highest in the 6-month to 1-year age group. Coinfection was observed in 36 HPIV-3-positive samples (35.29%, 36/102), and adenovirus (ADV) was the most common coinfecting virus (63.89%, 23/36). The L gene of 48 HPIV-3 positive samples was sequenced. The nucleotide sequence analysis showed high consistency (92.10%-99.40%), and all strains belonged to C3a.

CONCLUSIONS

During study periods, the positive detection rate of HPIV-3 among children is high, and the highest proportion of coinfection was observed in HPIV-3 mixed ADV infection. Phylogenetic analysis revealed that the nucleotide sequence of the L gene of HPIV-3 was highly consistent, and the main epidemic strain in this area was the C3a subtype.

Clinical Characteristics of Pediatric Parainfluenza Virus Infections: A Comparative Analysis of Parainfluenza Virus Serotypes 1-4 From April 2021 to October 2023 in Hokkaido, Japan

BACKGROUND

Parainfluenza virus (PIV) is widely known as a causative virus of acute respiratory tract infections in children, and 4 serotypes (PIV-1-PIV-4) have been identified. The purpose of the present study was to clarify the clinical characteristics of the PIV serotypes in pediatric PIV infections in Japan.

METHODS

Between April 2021 and October 2023, 8821 children aged <16 years who presented with respiratory symptoms underwent multiplex polymerase chain reaction analyses at the Department of Pediatrics, NTT Medical Center Sapporo. All 1490 cases in which PIV was detected were analyzed for their clinical characteristics by PIV serotypes.

RESULTS

Of the 1490 cases, 608 were positive for a single PIV serotype: 91 (13.5%) for PIV-1, 54 (4.8%) for PIV-2, 361 (62.1%) for PIV-3 and 102 (19.6%) for PIV-4. The median ages were 3.5 years for PIV-1, 5.4 years for PIV-2, 1.9 years for PIV-3 and 2.2 years for PIV-4, with a significantly older age for PIV-2. Compared with the other serotypes, croup was significantly more common in PIV-1 and lower respiratory tract infection was significantly more common in PIV-4. Of the 608 cases with a single PIV serotype, 114 were hospitalized. The proportion of hospitalized patients was higher for PIV-4 than for the other PIV serotypes, but the difference was not significant.

CONCLUSIONS

Lower respiratory tract infection was more frequent in PIV-4 than in the other PIV serotypes, and PIV-4 infection may increase the risk of hospitalization.

Genetic analysis of human parainfluenza type 2 virus in Riyadh, Saudi Arabia

The extensive mass gathering of pilgrims from all over the world, as well as the constant flow of foreign workers via country entry crossings, raises the likelihood of respiratory virus outbreaks spreading and evolving in Saudi Arabia. Here, we report the sequence and phylogenetic analysis of the human parainfluenza type-2 (HPIV-2) in nasopharyngeal aspirates (NPAs) collected from Riyadh, Saudi Arabia, from 2020/21 to 2021/22 seasons. RNA was extracted from the clinical samples and subjected to RT-PCR analysis for the detection of IAV and IBV. The full-length HN gene of HPIV-2 was amplified and sequenced. Multiple sequence alignments (both nucleotides and deduced amino acids) were aligned using Clustal W, MegAlign program of Lasergene software, and MEGA 7.0. HPIV-2 was found in (4; 2% of 200) NPAs. Sequence and phylogenetic analysis results showed that indicated a genotype shifting from G3 to G4a with 83% sequence homology 62-M786 from Japan, which was prominent throughout the winter seasons of 2008/09. Multiple amino acid sequence alignment revealed 25 sites of possible difference between G3 genotypes and G4a. A total of twenty- two of these locations were shared by the other G4a genotypes, whereas three positions, 67 V, 175 S, and 377Q, were exclusively shared by G3. Only eight conserved N-glycosylation sites were found at amino acids 6(NLS), 286(NTT), 335(NIT), 388(NNS), 498(NES), 504(NPT), 517(NTT), and 539(NGT) in four Riyadh isolates. Our findings also revealed that the G4a genotype of HPIV-2 predominated in our samples population during the winter seasons of 2020/21 and 2021/22. Further research with a larger sample size covering numerous regions of Saudi Arabia throughout different epidemic seasons is needed to achieve an improved knowledge of HPIV-2 circulation.

Human Parainfluenza Virus (HPIV) Detection in Hospitalized Children with Acute Respiratory Tract Infection in the Western Cape, South Africa during 2014-2022 Reveals a Shift in Dominance of HPIV 3 and 4 Infections

The epidemiology of human parainfluenza viruses (HPIV), particularly its role as a cause of acute respiratory infection (ARI) in infants, has not been formally studied in South Africa. We evaluated HPIV prevalence in diagnostic samples from hospitalized children from public sector hospitals in the Western Cape between 2014 and 2022. HPIV infection was detected in 2-10% of patients, with the majority of infections detected in children less than 1 year of age. Prior to 2020, HPIV 4 (40%) and HPIV 3 (34%) were the most prevalent types, with seasonal peaks in late winter/spring for HPIV 3 and autumn/winter for HPIV 4. HPIV 4A and 4B co-circulated during the seasonal activity between 2014 and 2017. Pandemic restrictions in 2020 had a profound effect on HPIV circulation and the rebound was dominated by waves of HPIV 3, accounting for 66% of detections and a sustained decline in the circulation of HPIV 1, 2 and 4. An immunity gap could account for the surge in HPIV 3 infections, but the decline in prior HPIV 4 dominance is unexplained and requires further study.

Contribution of the FilmArray BioFire® Technology in the Diagnosis of Viral Respiratory Infections during the COVID-19 Pandemic at Ibn Sina University Hospital Center in Rabat: Epidemiological Study about 503 Cases

Respiratory viruses are the most involved pathogens in acute respiratory infections. During the COVID-19 pandemic, new elements have been brought to this topic, especially at the diagnostic and therapeutic level. The objective of this work is to describe the epidemiology of respiratory viruses in patients admitted to the Ibn Sina University Hospital of Rabat during a period characterized by the emergence and spread of SARS-CoV-2. We conducted a retrospective study from January 1 to December 31. We included all patients treated for acute respiratory infection and for whom a multiplex respiratory panel PCR was requested. Virus detection was performed using a FilmArray RP 2.1 plus BioFire multiplex respiratory panel. The study population was relatively adults with a mean age of 39 years. The sex ratio M/F was 1.20. The survey revealed a high prevalence of 42.3% of patients hospitalized in the adult intensive care unit whose respiratory distress was the most common reason for hospitalization (58%). The positivity rate was 48.1%. This rate was higher in the pediatric population 83.13% compared to adults 29.7%. Monoinfection was found in 36.4% of cases, and codetection in 11.7% of cases. This survey revealed that a total of 322 viruses were detected, HRV being the most incriminated virus (48.7%), followed by RSV in 13.8% of patients. Considering the five most detected viruses in our study (HRV, RSV, PIV3, ADV, and hMPV), we found that the incidence was significantly higher in the pediatric population. SARS-CoV-2 was detected only in adult's population. In our study, we found that influenza A and B viruses, PIV2, MERS, and all bacteria were not detected by this kit during the study period. Regarding the seasonal distribution, RSV and hMPV showed a significantly high incidence during autumn and summer and SARS-CoV-2 and CoV OC43 showed a high peak during winter. In this study, we found a lack of detection of influenza virus and a shift in the usual winter peak of RSV to the summer, while the detection of ADV and HRV was less affected. This difference in detection could be due on the one hand to the difference in stability between enveloped and nonenveloped viruses and on the other hand to the escape of certain viruses to the different sanitary measures introduced after the declaration of the COVID-19 pandemic. These same measures were effective against enveloped viruses such as RSV and influenza viruses. The emergence of SARS-CoV-2 has modified the epidemiology of other respiratory viruses, either directly by viral interference or indirectly by the preventive measures taken.

Molecular Evolution of Human Parainfluenza Virus Type 2 Based on Hemagglutinin-Neuraminidase Gene

To understand the molecular evolution of human parainfluenza virus type 2 (HPIV2), 21 Hemagglutinin-Neuraminidase (HN) gene sequences covering seven Chinese provinces in 2011 and 2017 to 2021 were combined with 90 published HN sequences worldwide for phylogenetic analysis. The result showed that global HPIV2 could be classified into two distinct clusters (I and II), five lineages (IA to IIE), and four sublineages (IB1 and 2, and IIE1 and 2). The minimum genetic distances between different clusters and lineages were 0.049 and 0.014, respectively. In the last decade, one lineage (IID) and three sublineages (IB1, IB2, and IIE1) have been cocirculating in China, with the sublineages IB2 and IIE1 dominating, while sublineages IB1 and IIE1 are dominant globally. In addition, the spread of HPIV2 had relative spatial clustering, and sublineage IB2 has only been detected in China thus far. The overall evolution rate of HPIV2 was relatively low, on the order of 10-4 substitutions/site/year, except for sublineage IB2 at 10-3 substitutions/site/year. Furthermore, human-animal transmission was observed, suggesting that the HPIV2 might have jumped out of animal reservoirs in approximately 1922, the predicted time of a common ancestor. The entire HN protein was under purifying/negative selection, and the specific amino acid changes and two novel N-glycosylation sites (N316 and N517) in sublineages IB1, IB2, and IIE1 were mostly located in the globular head region of the HN protein. In this study, preliminary evolutionary characteristics of HPIV2 based on the HN gene were obtained, increasing the recognition of the evolution and adaptation of HPIV2. IMPORTANCE The phylogenetic analysis showed that global HPIV2 could be classified into two distinct clusters (I and II) and five lineages (IA to IIE) with at least 0.049 and 0.014 genetic distances between clusters and lineages, respectively. Furthermore, lineages IB and IIE could be further divided into two sublineages (IB1-2 and IIE1-2). All China sequences belong to one lineage and three sublineages (IB1, IB2, IID, and IIE1), among which sublineages IB2 and IIE1 are predominant and cocirculating in China, while sublineages IB1 and IIE1 are dominant globally. The overall evolution rate of HPIV2 is on the order of 10-4 substitutions/site/year, with the highest rate of 2.18 × 10-3 for sublineage IB2. The entire HN protein is under purifying/negative selection, and the specific amino acid substitutions and two novel N-glycosylation sites (N316 and N517) in sublineages IB1, IB2, and IIE1 are mostly located in the globular head region of the HN protein.

Comparison of Respiratory Pathogens in Children With Lower Respiratory Tract Infections Before and During the COVID-19 Pandemic in Shanghai, China

OBJECTIVES

This study aimed to assess the impact of COVID-19 on the prevalence of respiratory pathogens among hospitalized children with lower respiratory tract infections (LRTIs) in Shanghai.

METHODS

Respiratory specimens were collected from children with LRTIs in Children's Hospital of Fudan University from February 2019 to January 2021 and common respiratory pathogens were detected using multiplex PCR. The data of 13 respiratory pathogens were analyzed and compared between the year of 2020 (from February 2020 to January 2021) and 2019 (from February 2019 to January 2020).

RESULTS

A total of 1,049 patients were enrolled, including 417 patients in 2019 and 632 patients in 2020. In 2020, 27.53% of patients were tested positive for at least one pathogen, which was significantly lower than that in 2019 (78.66%). The top three pathogens were Mycoplasma pneumoniae (Mp), human adenovirus (ADV) and human rhinovirus (RV) in 2019, whereas RV, human respiratory syncytial virus (RSV) and human parainfluenza virus (PIV) were the predominant ones in 2020. The positive rates of Mp, ADV, RV, PIV, Influenza virus B (InfB), H3N2, and H1N1 were significantly decreased in 2020. RV was the most detectable respiratory pathogen in 2020, and become the most frequent pathogen in all five age groups. PIV had a high prevalence from October to December 2020 which was even higher than that in 2019. Influenza virus A (InfA) was not detected in 2020. Co-infection was significantly less frequent in 2020.

CONCLUSION

The public health interventions aiming to eliminate COVID-19 have great impact on the prevalence of common respiratory pathogens. The prevalence of RV and PIV reminds us a possible resurgence of some pathogens.

Parainfluenza Virus Types 1-3 Infections Among Children and Adults Hospitalized With Community-acquired Pneumonia

BACKGROUND

Parainfluenza virus (PIV) is a leading cause of lower respiratory tract infections. Although there are several distinct PIV serotypes, few studies have compared the clinical characteristics and severity of infection among the individual PIV serotypes and between PIV and other pathogens in patients with community-acquired pneumonia.

METHODS

We conducted active population-based surveillance for radiographically confirmed community-acquired pneumonia hospitalizations among children and adults in 8 US hospitals with systematic collection of clinical data and respiratory, blood, and serological specimens for pathogen detection. We compared clinical features of PIV-associated pneumonia among individual serotypes 1, 2, and 3 and among all PIV infections with other viral, atypical, and bacterial pneumonias. We also compared in-hospital disease severity among groups employing an ordinal scale (mild, moderate, severe) using multivariable proportional odds regression.

RESULTS

PIV was more commonly detected in children (155/2354; 6.6%) than in adults (66/2297; 2.9%) (P < .001). Other pathogens were commonly co-detected among PIV cases (110/221; 50%). Clinical features of PIV-1, PIV-2, and PIV-3 infections were similar to one another in both children and adults with pneumonia. In multivariable analysis, children with PIV-associated pneumonia exhibited similar severity to children with other nonbacterial pneumonia, whereas children with bacterial pneumonia exhibited increased severity (odds ratio, 8.42; 95% confidence interval, 1.88-37.80). In adults, PIV-associated pneumonia exhibited similar severity to other pneumonia pathogens.

CONCLUSIONS

Clinical features did not distinguish among infection with individual PIV serotypes in patients hospitalized with community-acquired pneumonia. However, in children, PIV pneumonia was less severe than bacterial pneumonia.

Genetic Characteristics of Human Parainfluenza Virus Types 1-4 From Patients With Clinical Respiratory Tract Infection in China

Human parainfluenza viruses (HPIV1–4) cause acute respiratory tract infections, thereby impacting human health worldwide. However, there are no current effective antivirals or licensed vaccines for infection prevention. Moreover, sequence information for human parainfluenza viruses (HPIVs) circulating in China is inadequate. Therefore, to shed light on viral genetic diversity and evolution, we collected samples from patients infected with HPIV1–4 in China from 2012 to 2018 to sequence the viruses. We obtained 24 consensus sequences, comprising 1 for HPIV1, 2 for HPIV2, 19 for HPIV3, and 2 for HPIV4A. Phylogenetic analyses classified the 1 HPIV1 into clade 2, and the 2 HPIV4 sequences into cluster 4A. Based on the hemagglutinin-neuraminidase (HN) gene, a new sub-cluster was identified in one of the HPIV2, namely G1c, and the 19 HPIV3 sequences were classified into the genetic lineages of C3f and C3a. The results indicated that HPIV1–4 were co-circulated in China. Further, the lineages of sub-cluster C3 of HPIV3 were co-circulated in China. A recombination analysis indicated that a putative recombination event may have occurred in the HN gene of HPIV3. In the obtained sequences of HPIV3, we found that two amino acid substitution sites (R73K in the F protein of PUMCH14028/2014 and A281V in the HN protein of PUMCH13961/2014) and a negative selection site (amino acid position 398 in the F protein) corresponded to the previously reported neutralization-related sites. Moreover, amino acid substitution site (K108E) corresponded to the negative selection site (amino acid position 108) in the 10 F proteins of HPIV3. However, no amino acid substitution site corresponded to the glycosylation site in the obtained HPIV3 sequences. These results might help in studying virus evolution, developing vaccines, and monitoring HPIV-related respiratory diseases.

Microfluidic sample preparation for respiratory virus detection: A review

Techniques used to prepare clinical samples have been perfected for use in diagnostic testing in a variety of clinical situations, e.g., to extract, concentrate, and purify respiratory virus particles. These techniques offer a high level of purity and concentration of target samples but require significant equipment and highly trained personnel to conduct, which is difficult to achieve in resource-limited environments where rapid testing and diagnostics are crucial for proper handling of respiratory viruses. Microfluidics has popularly been utilized toward rapid virus detection in resource-limited environments, where most devices focused on detection rather than sample preparation. Initial microfluidic prototypes have been hindered by their reliance on several off-chip preprocessing steps and external laboratory equipment. Recently, sample preparation methods have also been incorporated into microfluidics to conduct the virus detection in an all-in-one, automated manner. Extraction, concentration, and purification of viruses have been demonstrated in smaller volumes of samples and reagents, with no need for specialized training or complex machinery. Recent devices show the ability to function independently and efficiently to provide rapid, automated sample preparation as well as the detection of viral samples with high efficiency. In this review, methods of microfluidic sample preparation for the isolation and purification of viral samples are discussed, limitations of current systems are summarized, and potential advances are identified.

A review on disease burden and epidemiology of childhood parainfluenza virus infections in Asian countries

Human parainfluenza viruses (HPIVs) are an important cause of acute respiratory tract infections (ARTIs) in children less than 5 years, second only to human respiratory syncytial viruses (HRSVs). Generally, patients infected with HPIVs are treated in outpatient clinics, yet also contribute to ARTI-associated hospitalization in children. Although HPIV infections are well studied in developed countries, these infections remain under-investigated and not considered in the routine laboratory diagnosis of childhood ARTI in many developing countries in Asia. We performed an extensive literature search on the prevalence, epidemiology, and burden of HPIV infections in children less than 5 years in Asia using PubMed and PubMed Central search engines. Based on the literature, the prevalence of HPIV infection in Asia ranges from 1% to 66%. According to many studies, HPIV-3 is the major virus circulating among children; however, several studies failed to detect HPIV-4 due to unavailability of diagnostic tools. In Asian countries, HPIV contributes a substantial disease burden in children. The data in this review should assist researchers and public health authorities to plan preventive measures, including accelerating research on vaccines and antiviral drugs.

Changes in the etiology of viral lower respiratory tract infections in hospitalized children in Wenzhou, China: 2008-2017

This study investigated the seasonality and secular trends in the etiology of viral lower respiratory tract infections (LRTIs) among hospitalized children in Wenzhou, southeastern China. A retrospective review was conducted concerning viral LRTIs in children hospitalized at a university hospital between January 1, 2008 and December 31, 2017. Direct immunofluorescence was used to detect respiratory syncytial virus (RSV), adenovirus (AdV), influenza A virus (Inf A), influenza B virus (Inf B), and human parainfluenza virus types 1 to 3 (hPIV1-3). Of 89 898 children tested, at least one viral respiratory pathogen was identified in 25.6% and multiple pathogens were identified in 0.4%. RSV (17.6%), hPIV3 (4.0%), and AdV (2.2%) were the most frequently detected pathogens. The proportion of positive samples varied with age and was the highest in children aged  <6 months (36.2%). Seasonal differences were observed in RSV, AdV, Inf A, Inf B, hPIV1, and hPIV3 infections. There was a declining trend in the proportion of positive samples over time, primarily due to a decrease in RSV and hPIV3 infections. RSV, hPIV3, and AdV were the most common viral respiratory pathogens identified among hospitalized children with LRTIs. The distribution of viruses varied with age and season.

Human parainfluenza virus circulation, United States, 2011-2019

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Human parainfluenza virus type 3 is the most commonly reported parainfluenza virus followed by types 1, 2, and 4, respectively.

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Each parainfluenza virus type exhibited a unique circulation pattern.

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Parainfluenza type 4 circulated annually and peaked during the winter months.

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There was no remarkable distinction in regional versus national seasonal circulation patterns.

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The majority of parainfluenza virus detections with available age data occurred among children aged ≤2 years.

Background

Human parainfluenza viruses (HPIVs) cause upper and lower respiratory tract illnesses, most frequently among infants and young children, but also in the elderly. While seasonal patterns of HPIV types 1–3 have been described, less is known about national patterns of HPIV-4 circulation.

Objectives

To describe patterns of HPIVs circulation in the United States (US).

Study design

We used data from the National Respiratory and Enteric Virus Surveillance System (NREVSS), a voluntary passive laboratory-based surveillance system, to characterize the epidemiology and circulation patterns of HPIVs in the US during 2011–2019. We summarized the number of weekly aggregated HPIV detections nationally and by US census region, and used a subset of data submitted to NREVSS from public health laboratories and several clinical laboratories during 2015–2019 to analyze differences in patient demographics.

Results

During July 2011 - June 2019, 2,700,135 HPIV tests were reported; 122,852 (5 %) were positive for any HPIV including 22,446 for HPIV-1 (18 %), 17,474 for HPIV-2 (14 %), 67,649 for HPIV-3 (55 %), and 15,283 for HPIV-4 (13 %). HPIV testing increased substantially each year. The majority of detections occurred in children aged ≤ 2 years (36 %) with fluctuations in the distribution of age by type.

Conclusions

HPIVs were detected year-round during 2011–2019, with type-specific year-to-year variations in circulation patterns. Among HPIV detections where age was known, the majority were aged ≤ 2 years. HPIV-4 exhibited an annual fall-winter seasonality, both nationally and regionally. Continued surveillance is needed to better understand national patterns of HPIV circulation.

Outbreak of Human Parainfluenza Virus Type 1 in a Kindergarten from China, 2018

Objective  We reported an outbreak of human parainfluenza virus type 1 (HPIV1) in a kindergarten and explored the genetic characteristics of HPIV1 hemagglutinin-neuraminidase (HN) and fusion (F) genes to provide more evidence about HPIV1 outbreaks.

Methods  Suspected cases were the children with an influenza-like illness during June 20 to 26, 2018. Nasopharyngeal swabs were collected and screened to determine the presence of respiratory pathogens by real-time fluorescent quantitative polymerase chain reaction. The HN and F gene sequences of HPIV-positive samples were further amplified and sequenced to confirm the HPIV genotype and identify genetic characteristics. A phylogenetic tree, based on the HN and F genes, was reconstructed by maximum likelihood method.

Results  Fourteen children in the outbreak were diagnosed as upper respiratory tract infection. The most common symptom was cough (10/14), followed by rhinorrhea (5/14), sore throat (4/14), headache (1/14), and abdominal pain (1/14). Eight patients were positive for HPIV1 and negative for other pathogens. Phylogenetic tree demonstrated that the eight strains from the year 2018 in our study located in the clade 2.3. Two specific substitutions (N333S and I509M) in the amino acids of the F protein and two substitutions (V19A and L436I) in the HN protein were different from other strains in the clade 2.

Conclusion  HPIV1 was attributed to the outbreak, which may be related to the genetic variations of HPIV1.

Clinical characteristics of the lower respiratory tract infection caused by a single infection or coinfection of the human parainfluenza virus in children

BACKGROUND

Human parainfluenza virus (HPIV), usually combined with other pathogens, causes lower respiratory tract infection (LRTI) in children. However, clinical characteristics of HPIV coinfection with other pathogens were unclear. This study aimed to investigate the viral and atypical bacterial etiology of LRTI in children and compare the clinical characteristics of HPIV single infection with those of coinfection.

METHODS

This study included 1335 patients, aged between 1 to 71 months, diagnosed with LRTI in Yuying Children's Hospital, Zhejiang, China, from December 2013 to June 2015. Nasopharyngeal secretions were collected, and respiratory pathogens were detected using Multiplex polymerase chain reaction. The clinical data of patients were collected and analyzed.

RESULTS

At least 1 pathogen was detected in 1181/1335 (88.5%) patients. The pathogens identified most frequently were respiratory syncytial virus, human rhinovirus, HPIV, adenovirus, and human metapneumovirus. The coinfection rate was 24.8%. HPIV coinfection with other viruses was more associated with running nose, shortness of breath, and oxygen support compared with HPIV single infection. Moreover, HPIV coinfection with atypical bacteria was more related to running nose, moist rales, and longer hospital duration compared with HPIV single infection, and also to longer hospital duration compared with coinfection with other viruses.

CONCLUSIONS

This study demonstrated that viral infections were highly associated with LRTI and the rate of coinfection was high. HPIV single infection was milder than coinfection with other viruses. Moreover, HPIV coinfection with atypical bacteria was more serious than HPIV single infection and coinfection with other viruses.

Viral pathogens associated with acute lower respiratory tract infections in children younger than 5 years of age in Bulgaria

Acute lower respiratory infections (ALRIs) are a leading cause of morbidity and hospital admissions in children. This study aimed to determine the viral etiology of these infections in children aged < 5 years during three successive epidemic seasons in Bulgaria. Nasopharyngeal and throat specimens were collected from children with bronchiolitis and pneumonia during the 2015/2016, 2016/2017, and 2017/2018 seasons. The viral etiology was determined by individual real-time PCR assays against 11 respiratory viruses. Of the 515 children examined, 402 (78.1%) were positive for at least one virus. Co-infections with two and three viruses were found in 64 (15.9%) of the infected children. Respiratory syncytial virus (RSV) was the predominant pathogen (37.5%), followed by rhinoviruses (13.8%), metapneumovirus (9.1%), adenoviruses (7%), bocaviruses (7%), influenza A(H1N1)pdm09 (4.9%), A(H3N2) (4.3%), type B (4.1%), and parainfluenza viruses 1/2/3 (2.9%). RSV-B were more prevalent than RSV-A during the three seasons. At least one respiratory virus was identified in 82.6% and 70.1% of the children with bronchiolitis and pneumonia, respectively. Respiratory viruses, especially RSV, are principal pathogens of ALRIs in children aged < 5 years. Diagnostic testing for respiratory viruses using molecular methods may lead to the reduced use of antibiotics and may assist in measures to control infection.

Seasonality and clinical impact of human parainfluenza viruses

Background

Widespread availability of rapid diagnostic testing for respiratory viruses allows more in‐depth studies of human parainfluenza viruses (HPIV).

Objectives

This study aimed to assess seasonality of HPIV types 1‐4, clinical outcomes by HPIV type, and risk factors for illness severity.

Patients/Methods

This retrospective study was performed from January 2013 to December 2015 in children and adults with HPIV, detected by multiplex reverse transcription polymerase chain reaction, participating in a community surveillance study of acute respiratory infections (ARIs) in New York City and patients admitted to a tertiary care center in the same neighborhood. Seasonality trends by HPIV type were compared between the community and hospital groups. The associations between HPIV type, demographics, clinical characteristics, and illness severity were assessed.

Results

HPIV was detected in 69 (4%) of 1753 community surveillance participants (median age 9.2 years) and 680 hospitalized patients (median age 6.8 years). Seasonality for HPIV types 1‐3 agreed with previously described patterns; HPIV‐4 occurred annually in late summer and fall. In the community cohort, 22 (32%) participants sought medical care, 9 (13%) reported antibiotic use, and 20 (29%) reported ≥1 day of missed work or school. Among hospitalized patients, 24% had ≥4 chronic conditions. Multivariable ordinal logistic regression demonstrated that increased severity of illness was significantly associated with HPIV‐4 and chronic cardiovascular and respiratory conditions in children and with age ≥65 years and chronic respiratory conditions in adults.

Conclusions

HPIV‐4 presented late summer and early fall annually and was associated with increased severity of illness in hospitalized children.

Functional analysis of amino acids at stalk/head interface of human parainfluenza virus type 3 hemagglutinin-neuraminidase protein in the membrane fusion process

Human parainfluenza virus type 3 (hPIV3) is an important respiratory pathogen that causes the majority of viral pneumonia of infants and young children. hPIV3 can infect host cells through the synergistic action of hemagglutinin-neuraminidase (HN) protein and the homotypic fusion (F) protein on the viral surface. HN protein plays a variety of roles during the virus invasion process, such as promoting viral particles to bind to receptors, cleaving sialic acid, and activating the F protein. Crystal structure research shows that HN tetramer adopted a "heads-down" conformation, at least two heads dimmer on flank of the four-helix bundle stalk, which forms a symmetrical interaction interface. The stalk region determines interactions and activation of F protein in specificity, and the heads in down position statically shield these residues. In order to make further research on the function of these amino acids at the hPIV3 HN stalk/head interface, fifteen mutations (8 sites from stalk and 7 sites from head) were engineered into this interface by site-directed mutagenesis in this study. Alanine substitution in this region of hPIV3 HN had various effects on cell fusion promotion, receptor binding, and neuraminidase activity. Besides, L151A also affected surface protein expression efficiency. Moreover, I112A, D120A, and R122A mutations of the stalk region that were masked by global head in down position had influence on the interaction between F and HN proteins.