Viral Pathogens Associated with Acute Lower Respiratory Infections Among Hospitalized Children in Yangon Children’s Hospital

Han Win, Htin Lin, Mo Mo Win, Lay-Myint Yoshida, Wah Wah Aung, Hlaing Myat Thu & Ye Myint Kyaw

Myanmar Health Sciences Research Journal, 2020; 32(2): 180-184

Viruses are common causes of lower respiratory tract disease in infants and young children and represent a major public health problem in children. The present study aimed to identify viral etiological agents of acute lower respiratory infections (ALRI) among children admitted to Yangon Children’s Hospital from February 2014 to August 2015. Clinical data and nasopharyngeal swab (NP) samples were collected. Four multiplex polymerase chain reaction assays were performed to detect 13 respiratory viruses in each NP sample. A total of 390 were enrolled. The age of the children ranged from one to 108 months with median age of 12 months. Of all study children, 202(51.8%) were non-severe ALRI and 188(48.2%) were severe ALRI cases. Presence of wheeze (p=0.001), attendance at kindergarten (p=0.01) and higher total WBC counts(p=0.004) were significantly associated with severe ALRI. Among 390 samples, 157(40.3%) were positive for at least one respiratory virus. Major viruses detected were rhinovirus (72, 18.5%), respiratory syncytial virus (30, 7.7%), adenovirus (17, 4.4%) and parainfluenza virus 3 (17, 4.4%). Respiratory syncytial virus(OR=1.35, 95% CI=1-1.8) and influenza A virus (OR=1.63, 95% CI=1.2-2.24) were associated with diagnosis of severe ALRI, but adenovirus (OR=0.35, 95% CI=0.13-0.99) was found to be related to less risk of severe ALRI. This study showed that rhinovirus, respiratory syncytial virus, adenovirus and parainfluenza virus 3 were leading cause of ALRI in hospitalized children and suggested that respiratory syncytial virus and influenza A virus may increase the severity of ALRI.

A total of 390 patients were enrolled in the study. Ages ranged from one month to 9 years with median age of 12 months. They included 225 boys (57.7%) and 165 girls (42.3%). The mean duration from disease onset to admission was 3.5 days.Thirty-five patients (8.9%) had attended daycare or kindergarten at the time of illness.

Table 1. Background characteristics of study population

Of all study children, 202(51.8%) were non-severe ALRI and 188(48.2%) were severe ALRI.Presence of wheezing (p=0.001), higher total WBC counts (p=0.004), and attendance at kindergarten (p=0.01) were significantly associated with severe ALRI (Table 1).

Viral etiologies

Among 390 samples, 157(40.3%) were positive for at least one respiratory virus. Major viruses detected were human rhinovirus (72, 18.5%), RSV (30, 7.7%), adenovirus (17, 4.4%), parainfluenza virus 3(17, 4.4%), and influenza A virus (13, 3.3%). Newly identified viruses were also detected; HCoV(2%), HBoV (2%) and HMPV (0.8%) (Table 2). Of all ARI cases,28(7.2%) were multiple viral infections which included 25(6.4%) dual infections and3(0.8%) triple infections.

Table 2. Respiratory  viruses detected in study samples(n=390)

Table 3. Effect of common respiratory viruses on the risk of severe ALRI

ALRI = Acute lower respiratory tract infection

Common viruses and risk of severe ALRI

Table 3 shows the effect of common respiratory viruses on the risk of severe ALRI. Respiratory syncytial virus (OR=1.35, 95% CI=1-1.8) and influenza A virus (OR=1.63, 95% CI=1.2-2.24) were associated with diagnosis of severe ALRI, but adenovirus (OR=0.35, 95% CI=0.13-0.99) was found to be related to less risk of severe ALRI.

The development of molecular methods such as conventional or real-time reverse transcriptase polymerase (RT-PCR) has facilitated rapid and sensitive simultaneous diagnostic detection of the variety of viruses causing respiratory tract infection.5 However, limited resources and facilities preclude
the routine use of molecular diagnostics in tropical lower-income countries. As a consequence, insight into the aetiology of ARIs is lowest in regions of the world where morbidity and mortality are highest. Better understanding of the full spectrum of respiratory viruses causing ARIs in hospitalized patients in these settings is essential for improving preventive and therapeutic strategies.6There is a limited data on viral etiology of childhood ARI in Myanmar. In the present study, hospitalized Myanmar children with ARI were investigated for 13 viral pathogens using multiplex-polymerase chain reaction (PCR).

Laboratory analysis

Nasopharyngeal samples collected were stored at-80ºC. Viral RNA was extracted from the samples by using QIAamp RNA Mini Kits according to the manufacturer’s instructions. Four multiplex polymerase chain reaction (PCR) assays (assay 1: FLU A, FLU B, RSV, hMPV; assay 2: parainfluenza virus 1-4; assay 3: HRV, human coronavirus 229E (HCoV-229E), human coronavirus OC43 (HCoV-OC43); assay 4: adenovirus and human bocavirus(HBoV) were performed to detect 13 respiratory viruses in the samples. QIAGEN one step RT-PCR kits and TaqDNA polymerase (Promega, San Luis Obispo, CA) were used for thepreparation of PCR mixtures. Positive RNA templates of each respiratory virus were used for quality control.

Data analysis

Clinical characteristics were compared between ALRI categories (non-severe vs. severe) using Chi-squared test and Student’s t test. The effect of each viral infection on the risk of an ALRI being diagnosed as severe was assessed using univariate analysis, and expressed as odds ratio with 95% confidence intervals (95% CI).

Ethical consideration

The study was approved by the Ethics Review Committee of Department of Medical Research. Written informed consents were obtained from the guardians of all study children.

In the present study, respiratory viral agents were detected in 40% of cases, which is rather different from that of other studies. In a study among hospitalized children in central Vietnam, virus detection rate was 69% but in a Korean study it was only 22%.8, 9The prevalence of viral pathogens associated with ARI may vary in different countries with different geographic and climatic characteristics. The spectrum of major viral pathogens identified in our study was similar to those of previous studies in Vietnam and South Korean.8, 10 However, there were some differences in terms of proportion. Our study showed a lower proportion of RSV and influenza A virus compared with either Vietnam or South Korea.Although human rhinovirus infection was most commonly detected, the etiological role of HRV in hospitalized ARI cases is questionable. Previous reports showed frequent detection of HRV in apparently healthy children.11, 12 There could be some underlying reasons for why HRV was associated with ALRI while high HRV detection rate among healthy children. Viral load and serotypes may play a role. ARI patients may have higher HRV loads than healthy control and/or infected with more pathogenic serotypes. Another possibility may be co-infection with other undetected respiratory viruses or bacteria.No viruses were detected in 60% of cases in this study. It was possible that some children may have infection with other viruses not included in our assays(eg. enteroviruses).

In addition, some may have cleared their viral infection before the collection of clinical samples.It was also believed that bacterial infections accounted fora substantial proportion of ARI among hospitalized children. In this study, severe ALRI cases were associated with wheezing or higher total WBC counts. These findings suggest that our severe ALRI cases may have included many bronchiolitis cases or cases with bacterial infection/co-infections. Our study also revealed that RSV and influenza A virus were found to have an association with severe ALRI cases, a finding which is compatible with a number of other studies.13, 14, 15

Limitations of the study

Since this study was only 18 months, we cannot conclude on the seasonality of the viruses that were detected. Multiplex PCR assays were used to detect 13 common respiratory viruses with high sensitivity. However, there is a possibility that some other viruses, which were not in our detection system, might be circulating in hospitalized children in YCH. This study used the modified WHO IMCI algorithms to define ALRI instead of radiologically confirmed pneumonia.

Conclusion

This study showed that rhinovirus, respiratory syncytial virus, adenovirus, parainfluenza virus 3 and influenza A were most commonly detected in hospitalized ALRI childrenin YCH. Newly identified viruses such as HCoV, HBoV and hMPV were also implicated. The study also suggested that respiratory syncytial virus and influenza A virus may increase the severity of ALRI.

The authors declare that they have no competing interests.