Respiratory Viruses Associated With Acute Wheezing in Hospitalized Young Children in Jordan

Abstract

A cross-sectional viral surveillance study of hospitalized children less than 2 years of old in Amman, Jordan, noted that respiratory syncytial virus and human metapneumovirus, but not human rhinovirus, were associated with higher odds of acute wheezing. Future longitudinal studies are needed to evaluate the association between early childhood viral acute respiratory infections and recurrent wheezing later in childhood.

Wheezing affects approximately one-third of children at least once by the age of 9 years and causes significant morbidity and mortality in young children worldwide [1]. It is often associated with various lower respiratory tract infections (LRTIs), specifically respiratory syncytial virus (RSV), human rhinovirus (HRV), human metapneumovirus (HMPV), influenza viruses, parainfluenza viruses (PIVs), and coronavirus [1]. While wheezing is transient in most of the children, 40% of them develop recurrent wheezing or asthma by the age of 5 years [2].

Viral-associated wheezing and LRTIs during infancy are associated with subsequent asthma, so it is important to determine viruses, among other risk factors, that are associated with wheezing. Few studies in the Middle East focus on the association between wheezing and respiratory viruses, including highly sensitive molecular techniques [3]. Data are needed to guide preventive interventions against wheezing illness in the region. Therefore, our study aimed to determine the association between acute wheezing illness and respiratory viruses and other clinical and demographic characteristics in hospitalized children in Jordan.

METHODS

Study Design and Population

This cross-sectional study was a sub-study of our prospective viral surveillance study of hospitalized children at a large government hospital, Al Bashir, in Amman, Jordan, from March 16, 2010, and March 31, 2013 [4]. Details about the study design, setting, and methodology have been previously published [4]. In short, children less than 2 years of old were enrolled 5 days a week within 48 hours of hospital admission with fever and/or respiratory symptoms. Febrile neutropenic children and newborns never discharged from the hospital were excluded. The Institutional Review Boards approved this study at Vanderbilt University Medical Center (VUMC), Jordan University, and the Jordanian Ministry of Health. Written informed consent was obtained from parents/guardians.

Demographic and Clinical Information

Study personnel collected demographic and clinical characteristics by interviewing parents or guardians and extracting information from medical records. The treating physician prospectively recorded physical examination findings, including wheezing on a standardized case report form. Data were entered into a standardized, secured database—Research Electronic Data Capture system [5].

Specimen Collection and Viral Testing

Nasal and throat swabs were collected and combined into transport medium (M4RT, Remel), aliquoted into MagMAXTM Lysis/Binding Solution Concentrate (Life Technologies), snap-frozen, and stored at −80°C. Original and lysis buffer aliquots were shipped to VUMC on dry ice and were tested using quantitative reverse transcription polymerase chain reaction (qRT-PCR) assays directed at primers and probes as previously published for: RSV, HRV, HMPV, influenza viruses A and B, PIVs 1, 2, and 3, adenovirus, and Middle East respiratory syndrome coronavirus [4].

Statistical Analysis

Summary statistics were presented as median with interquartile range (IQR), mean (standard deviation), or percentage (frequency) where appropriate. Univariable logistic analysis and linear regression were used to compare binary and continuous variables, respectively, between wheezing and non-wheezing patients.

To assess the association between demographic and clinical characteristics and viruses with the primary outcome of interest (ie, wheezing), multivariable logistic regression was used to determine the odds ratios (OR) for wheezing across a priori selected predictors of interest, including age, sex, smoke exposure, breastfeeding history, birthweight, type of delivery, prematurity, personal, maternal and family history of asthma, and virus type. All analyses had a significance level of 0.05 (2-tailed) and were performed using StataCorp, College Station, TX software (version 15.1).

RESULTS

Clinical and Demographic Characteristics

During the study period, 3793 children were eligible and 3168 (83.5%) were included in the final cohort. The median age at enrollment was 3.5 months, and 60% were male [4]. Overall, 2581 (81.5%) had at least 1-virus detected, and 1757 children (55%) had wheezing diagnosed by a physician.

Wheezing and Non-wheezing Children

On univariable analysis, children with wheezing were older; more likely to have underlying medical history; personal history of reactive airway disease (RAD), allergic rhinitis, and atopy; family history of asthma; receive oxygen therapy; have an abnormal chest X-ray; a shorter length of stay, but less likely to have a history of breastfeeding or present with fever compared with non-wheezing children (Table 1). There were no differences in smoke exposure, prematurity, maternal history of atopy, or intensive care unit admission between the two groups (Table 1).

Table 1.

Univariable Comparisons of Demographic and Clinical Characteristics Between Wheezing vs Non-wheezing Children

	Wheezing n = 1757	Non-wheezing n = 1411	P-value
Age, months, mean ± SD	6.7 ± 5.6	4.6 ± 5.3	<.001**
Age, months, median [IQR]	5 [2.4–9.6]	2.1 [1.2–6.3]
Male	1075 (61.2%)	837 (59.3%)	.286*
History of or current breastfeeding	1452 (82.6%)	1209 (85.7%)	.020*
Smoke exposure	1364 (77.6%)	1061 (75.2%)	.108*
Cesarean section delivery	483 (27.5%)	410 (29.1%)	.330*
Birthweight, kg, mean ± SD	2.98 ± 0.7	2.96 ± 0.7	.508**
Prematuritya	252 (14.3%)	198 (14%)	.804*
Underlying medical conditions	208 (11.8%)	112 (7.9%)	<.001*
Child history of atopy	145/1756 (8.3%)	53/1408 (3.8%)	<.001*
Reactive airway disease	68/1756 (3.9%)	11/1408 (0.8%)	<.001*
Eczema	12 (0.7%)	6 (0.4%)	.343*
Allergic rhinitis	80 /1755 (4.6%)	39/1409 (2.8%)	.009*
Mother history of atopy	242 (13.8%)	191 (13.5%)	.847*
Asthma	53 (3%)	38 (2.7%)	.588*
Eczema	67 (3.8%)	55 (3.9%)	.902*
Allergies	150 (8.5%)	116 (8.2%)	.750*
Family history of asthma	435 (24.8%)	285 (20.2%)	.002*
Fever	892 (50.8%)	870 (61.7%)	<.001*
Oxygen therapy	647 (37.2%)	366 (26.2%)	<.001*
Mechanical ventilation	69 (4%)	42 (3%)	.151*
Intensive care unit	168 (9.6%)	116 (8.2%)	.189*
Abnormal chest X-ray	1496/1717 (87.1%)	581/1244 (46.7%)	<.001*
Length-of-stay, days, mean ± SD	5.2 ± 3.9	6.1 ± 4.2	<.001**

Bold indicates P value < .05.

Categorial data are in n (%); continuous data are in mean ± SD, median [IQR].

Abbreviations: n, number; SD, standard deviation; IQR, interquartile range.

^aPrematurity is defined as birth at gestational age less than 37 weeks.

*Logistic regression; **Linear regression.

In the wheezing group, viral detection was higher compared to non-wheezers (88% vs 74%, P < .005). Figure 1 illustrates that compared with non-wheezing children, those with wheezing had a higher frequency of RSV (53% vs 33%), HMPV (11% vs 6%), but no difference in HRV detection.

Figure 1.

Comparison of wheezing and non-wheezing groups by frequency of virus detection.

Effect of Viruses and Clinical/Demographic Factors on Wheezing

Using a multivariable logistic regression model, older age (OR: 1.082; 95% Confidence Intervals [CI]: 1.064-1.100), RSV (OR: 2.726; 95% CI: 2.324-3.196), HMPV (OR: 2.330; 95% CI: 1.729-3.138), family history of asthma (OR: 1.231; 95% CI: 1.029-1.473), and personal history of RAD (OR: 3.556; 95% CI: 1.808-6.994) were associated with increased odds of wheezing. No association between wheezing and sex, gestational age, birth weight, prematurity, delivery method, smoke exposure, breastfeeding, maternal asthma, influenza virus, PIVs, Adenovirus (AdV), or HRV (P > .05) was noted.

DISCUSSION

In our large viral prospective study investigating the burden of multiple respiratory viruses in young hospitalized children in Jordan, more than half of the children presented with wheezing, and the vast majority of children had virus detected. The most frequently detected viruses in wheezing children were RSV, HRV, AdV, and HMPV.

Other studies have demonstrated a similar relative proportion of RSV and HRV detected in children hospitalized with wheezing illness; in a Japanese study including hospitalized children below the age of 3 years with LTRIs, 33% RSV, 14% HRV, and 3% HMPV were detected in wheezing children [6]. In a 4-year study of infants less than 12 months hospitalized with bronchiolitis, 76% had RSV, 18% HRV, 3% HMPV, 10% influenza, 2% coronaviruses, and 1% PIVs [7].

We also found that RSV and HMPV were detected in a significantly higher percentage of children with wheezing than in those without wheezing, and this persisted after adjusting for multiple variables. Supporting our findings, RSV has been reported to be the leading cause of LRTIs requiring hospitalization in young infants [8]. HMPV has also been identified as an important pathogen in upper and lower RTIs [9]. Studies of children with acute LRTIs reported HMPV frequency similar to our cohort, ranging from 2% to 13%, including hospitalized children in the Middle East [3, 6–8]. Given that HMPV resembles RSV infection cytopathologically, clinically, and epidemiologically, it is not surprising that it was found to be an important contributor to wheezing illness in our study.

The utilization of PCR techniques has revealed the substantial prevalence of HRV in both upper and lower RTIs, including wheezing and asthma exacerbation. However, while HRV was identified in a significant proportion of young, hospitalized patients in our study, we did not observe a significant difference in HRV among those with wheezing vs those without wheezing. The prevalence of HRV in patients with wheezing and/or bronchiolitis increases with age and is more common in children with recurrent wheezing [1, 7]. A Finnish study looking at hospitalized children found that those with HRV infection were older than those with RSV infection [10]. Studies have also shown that HRV-associated wheezing is observed more frequently in atopic children and that maternal atopic asthma is a risk factor for HRV-associated wheezing [10]. Our hospitalized young cohort with less predominant personal and maternal atopic history may explain the predominant effect of RSV (and not HRV) on wheezing.

Children with wheezing had a higher proportion of personal history of RAD or family history of asthma than those without wheezing. Moreover, both were independently associated with increased OR of wheezing. However, maternal asthma was not associated with wheezing in our cohort, which could be due to our cohort’s low maternal asthma frequency. Further, according to the Tucson Children’s Respiratory Study, there are 4 patterns of wheezing in early childhood: never wheeze, transient early wheeze, late-onset wheeze, and persistent wheeze [11]. However, our study was not longitudinal, so we could not determine children’s ultimate wheezing phenotype. Other studies reported that most of the children who wheeze before 2 years of age do not develop recurrent wheeze or asthma later in childhood, and these children do not tend to have a history of maternal asthma or personal history of atopy [1, 12].

This study has both strengths and limitations. Given the large cohort, we were able to compare differences among multiple viruses and the association of wheezing. Further, wheezing was diagnosed by both clinical assessment and physical examination by a physician, making the diagnosis more reliable. It is also one of the few studies in Jordan/Middle East that used a highly sensitive qRT-PCR technique for detecting viruses in such a large cohort of hospitalized patients [4]. However, this was not a longitudinal study to conduct follow-up of children and determine if they developed recurrent wheezing or asthma later in life.

In summary, wheezing in young children under was associated with RSV and HMPV but not HRV. These data can be used to design future longitudinal studies to evaluate the association between early childhood viral acute respiratory infections and recurrent wheezing later in childhood and guide preventive interventions that would be most effective at preventing the development of wheezing illness.

Notes

Acknowledgment. We thank our research recruiters: Hanan Amin, Amani Altaber, Hana’a Khalaf, Isra’a Kharbat, Darin Yasin, Shireen Issa, and Nurse Sabah Gharbli and the families who participated in this study and the physicians of Al-Bashir.

Financial support. This work was supported by the UBS Optimus Foundation, National Institutes of Health, and the CTSA award (UL1TR000445) from the National Center for Advancing Translational Sciences. Its contents are solely the responsibility of the authors and do not necessarily represent official views of the National Center for Advancing Translational Sciences or the National Institutes of Health.

Potential conflicts of interest. N. B. H., MD, MPH, receives grant support from Sanofi, Quidel, and speaker compensation from an education grant supported by Genentech. Sanofi also donated vaccines and influenza antibody testing for influenza vaccine trial. J. V. W., MD, is on the scientific board for Quidel, Independent Data Safely Monitoring Committee, GlaxoSmithKline, and scientific advisory board ID Connect. All the other authors have no conflicts of interest to disclose.

All authors have submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest. Conflicts that the editors consider relevant to the content of the manuscript have been disclosed.