Respiratory Syncytial Virus: Prevalence and Features among Hospitalized Lebanese Children

Background: Respiratory Syncytial Virus (RSV) is an important cause of acute respiratory tract infections among infants and children requiring hospitalization. No data is available concerning RSV epidemiological and demographic characteristics among Lebanese children. Methods: This is an observational comparative retrospective and prospective study including two RSV seasons from October 2012 till March 2014 conducted at Makassed General Hospital, Lebanon. RSV rapid antigen detection test (Respi-Strip) was used for detection of RSV in nasopharyngeal wash swabs collected from all children 0 to 13 years with acute respiratory symptoms admitted at our hospital. Enrolled patients were divided according to age group and Respi-Strip results. Clinical presentation, risk factors, management interventions, course in hospital and severity parameters were compared between the different groups. Assaf et al.; BJMMR, 6(1): 77-87, 2015; Article no.BJMMR.2015.185 Results: Among the 443 patients enrolled in the study, 98 (22.1%) were RSV positive. RSV was mostly found among younger ages (P<0.0001). Younger ages were most likely to present with moderate or severe respiratory distress (P=0.014). Patients with RSV had a more severe course during hospitalization in all parameters (P=0.0001). However, both groups received same management during their stay including bronchodilators, α-adrenergic, steroids and antibiotics despite the latest AAP guidelines. Conclusion: Respiratory Syncytial Virus is major cause of hospitalization among Lebanese children. It has a severe course even in previously healthy children and thus, immunoprophylaxis should be highly stressed on by clinicians.


INTRODUCTION
Acute respiratory tract infections are the leading cause of morbidity and hospitalizations in children less than 5 years as reported by the World Health Organization [1].
Respiratory syncytial virus (RSV) is one of the most important respiratory pathogens among infants and children and a major cause of hospitalization for bronchiolitis and pneumonia in infants [2][3][4][5][6][7]. RSV infections comprise 20% of lower respiratory tract infections, and the global RSV disease burden is estimated as 64 million cases and 160,000 deaths annually, with most of the deaths occurring in the developing countries [8,9]. In the United States, it is estimated that 51240 to 81985 annual hospitalization due to bronchiolitis among children less than 1 year was related to RSV infection between 1980 and 1996 [4] with unchanging rates also reported between 1996 and 2006 [7].
Respiratory syncytial virus, a single-stranded, negative-sense RNA virus and a member of the family Paramixoviridae, almost always causes symptomatic disease during first encounter with an infant ranging from a simple cold to severe bronchiolitis or pneumonia. Virtually all children under two years of age have contact with RSV; only about 10% require hospitalization for respiratory distress. Upper respiratory tract symptoms usually precede lower respiratory tract involvement by few days. Around 80% of patients have fever, and more than 90% present with cough.
Other symptoms include nasal congestion, tachypnea, wheezing, retractions, difficulty breathing, vomiting and otitis. Variability of the child's clinical status within minutes to hours is a characteristic of RSV lower respiratory tract disease [10].
Children with underlying chronic conditions are at higher risk for requiring hospitalization for RSV illness; however, other environmental and host factors including tobacco exposure, asthma, daycare center attendance and younger siblings have been reported to increase the risk in previously healthy infants for developing severe disease [10].
The significance of RSV infection is marked by its contagiousness. Spread of RSV is through large droplets of secretions or contact with contaminated secretions and introduction of virus into the family appears to occur most commonly through a school-aged child [11]. The period of viral shedding usually is three to eight days, but it may last up to four weeks in young infants [12].
RSV often is diagnosed accurately in young children based on the season plus a typical history and findings on physical examination. It is identified by viral isolation or by one of the numerous rapid assays. For infants, the nasal wash is the preferred method of obtaining a specimen [19,20].
Therapy for respiratory syncytial virus infection of the lower respiratory tract is primarily supportive [19]. Evidence-based practice guidelines for management of bronchiolitis published by the American Academy of Pediatrics in 2006 recommend supportive care with limited diagnostic testing and treatment [21].
Several studies have been conducted over the years to study the burden, prevalence, clinical characteristics and risk factors of RSV infections but to our knowledge, none has been conducted to date studying the epidemiology, burden and management in Lebanon.
Our study will address trends in hospitalization rates, epidemiology, and disease severity of respiratory tract infections caused by RSV among pediatric patients admitted to our institution.

Study Design
This is an observational comparative retrospective and prospective study that was conducted at Makassed General Hospital, Beirut, Lebanon; a tertiary referral medical center. All infants and children from 0 to 13 years of age presenting with signs of acute respiratory illness, with onset within the previous 7 days, including at least one of the following signs/symptoms: abnormal breath sounds, tachypnea (according to age), cough, rhinorrhea and respiratory distress (nasal flaring, chest indrawing, grunting) with or without fever who necessitated hospitalization were enrolled in the study, during the period extending from October 2012 to March 2014. The study period started with the application of RSV rapid antigen detection at our laboratories. Further cross-sectional analysis was done between two groups: the RSV group and non-RSV group for additional characterization.
The study was conducted after the approval of the research and ethical committee at the institutional review board. Informed consents were obtained from parents/guardians of all participants prior to enrollment.

Exclusion Criteria
All children who were above 13 years of age, cases in whom respiratory samples were not collected during hospitalization, patients with acute concomitant bacterial infection at time of admission and newborns who had not been discharged from the hospital were excluded from the study.

Demographics and Clinical Data
Medical records of enrolled subjects from October 2012 to the end of October 2013 with final discharge diagnosis including bronchiolitis (RSV or non-RSV), pneumonia, viral respiratory tract infection were thoroughly reviewed for the epidemiologic and demographic characteristics, clinical symptoms, disease parameters of severity (Silverman's score, length of stay, oxygen requirement, PICU admission, need for mechanical ventilation), chest radiography findings, and management strategies. Demographic data that was missing in the medical records was obtained by calling parents/guardians and interviewing them.
From November 2013 to March 2014, pediatric residents and interns completed a questionnaire by interviewing the parents/guardians at time of admission and then recorded the child's clinical symptoms, medical history, demographic information, social history and tobacco exposure history. Just before patient's discharge, questionnaire was reviewed and additional data including hospital stay duration, disease severity, management strategies in addition to nasopharyngeal wash results were recorded.

Sampling
One nasopharyngeal wash sample was collected from each child with immediate storage in viral transport media. Samples were obtained within 24hrs following patient's presentation and sent to the laboratory every day. The samples collected over night and on weekends were stored at 4°C for 24 hrs or frozen at -20°C if kept for longer periods, to be sent the next morning for examination.

Examination of Samples
Samples were examined within one hour of collection using RSV Respi-Strip test kits (CorisBioCocept ®, Belgium) as a rapid antigen detection test [22]. The principle of this point-of care test is that a nitrocellulose membrane is sensitized with a monoclonal antibody directed against RSV while a mobile anti-RSV monoclonal antibody is conjugated to colloidal gold particles. If the sample contains RSV, conjugate RSV complex binds to the anti-RSV antibody, revealing a red line on the test strip. Testing was performed following the manufacturer's instructions. Results were available within 2 hours after testing specimen. The sensitivity and the specificity of RSV Respi-strip test was found to be 92% and 98%, respectively, and the diagnostic efficacy was 95% [22].

Statistical Analysis
Data were presented as mean (standard deviation) or number (percent). Analysis was performed using SPSS version 19. Chi-square test and Anova were used to find any significant differences between the groups. P-value<0.05 was considered significant.

RESULTS
Two thousand six hundred thirty eight patients were admitted to the pediatric ward at Makassed General Hospital during the study period extending from the beginning of October 2012 till the end of March 2014. Medical charts with discharge diagnosis including bronchiolitis, pneumonia, upper respiratory tract infection, and viral respiratory tract infection were reviewed. Five hundred forty two (20.5%) patients out of the total admissions were admitted with signs of acute respiratory tract infections including cough, rhinnorhea, tachypnea, and respiratory distress with or without fever. Ninety nine patients were excluded because no respiratory samples were collected or had onset of respiratory symptoms of more than 7 days. Out of the remaining four hundred forty three patients who were enrolled in the study, ninety eight (22.1%) patients were RSV positive [ Fig. 1].  Table 1 describes the demographic characteristics of all four hundred forty three enrolled patients. 79.7% of all cases were between the ages of 0 and 2 years. Both genders were almost equally present (45.6% females compared to 54.4% males). The majority of the patients (88.3%) were full term children with history of breast feeding in half of the enrolled population (51.2%) and a mean duration not exceeding 6 months. Unfortunately, it was also noted that more than half of these patients (63%) had at least one family member who was a smoker. Most enrolled patients were previously healthy (85.1%), only (14.9%) had a previous underlying chronic condition [ Table 2].
In the study, we divided the RSV positive patients into 4 different subgroups according to age (0-1 month, 1-6 months, 6-24 months, 24 months). The most common presenting symptom was cough (88.7%), followed by fever (64.2%), other symptoms included dyspnea (50%), rhinnorhea (35.7%), lethargy (27.5%), apnea (12.2%), vomiting (20%), diarrhea (8.1%) and one patient had otitis and another had conjunctivitis. A vast majority (75.5%) of RSV positive patients had wheezes on auscultation, and 50% had moderate respiratory distress according to Silverman's score [ Table 3].  Table 3]. Table 4 compares the course of hospital stay among the different age groups who are RSV positive. No patients above 2 years of age needed supplemental oxygen, but 50% of those from 0 to 1 month of age did. Higher percentages among age groups (0-1 months) and (1-6 months) needed intensive care management with a highly significant P value (P< 0.0001). No statistically significant difference was detected among the 4 different age groups concerning radiographic findings on chest X-ray, presence of pneumonia, or complications. Only 3 patients required mechanical ventilation (3.06%) and these included one below the age of 1 month and 2 in the 1-6 months group. The risk factors and demographic characteristics were studied between the RSV positive and RSV negative infants and children [ Table 5]. RSV positive children were younger (mean age 8.45 months vs. 17.10 months, P<0.0001), were breast fed for shorter duration (4 vs. 7 months, P= 0.193) and had higher incidence of contact with another sick patient (P=0.002). Though it was unexpectedly noted that RSV positive patients were less likely to attend daycare probably because the majority were less than 1 year of age and mothers were housewives who cared of their infants at home however they were more likely to have siblings less than 5 years old at home who probably attended daycare or school (P= 0.005). When comparing the management strategies between the two groups, no clinically significant difference was found concerning the type of nebulizer used, antibiotics used, steroids, or the number of chest X-rays done. Normal saline nebulizer was used alone in only 28.9% of RSVpositive patients; all remaining patients needed additional nebulized medications. High flow nasal canula (HFNC) was used in just one RSVpositive patient and 3% of the RSV-positive patients compared to 0.9% in the RSV-negative group needed mechanical ventilation (P=0.098). Concerning RSV positive patients, out of the 79 (80.6%) who had a chest X-ray done, 53% had normal chest X-ray, 15% had changes of bronchiolitis and 31.6% had a confirmed pneumonia.
The most compelling differences were observed when comparing the severity parameters between the two groups [  [24], and 20% in Israel [25]. Hall CB et al also reported that RSV was identified in 919 of 5067 specimens (18%) and was associated with 20% of annual hospitalizations, 18% of emergency department visits, and 15% of office visits for acute respiratory infections from November through April in the United States [26]. However, no previous epidemiological data is available in Lebanon prior to this study.

Fig. 2. Respiratory syncytial virus seasonal variations in Lebanon compared to all other causes of acute respiratory tract infection
Despite the fact that the study included ages up to 13 years, the majority of enrolled patients (79.7%) were below 24 months of age, and this is attributed to the fact that bronchiolitis is a disease confined to this age group as by AAP definition "a constellation of clinical symptoms and signs including a viral upper respiratory prodrome followed by increased respiratory effort and wheezing in children less than 2 years of age" [27]; with RSV being one of its major causes causing symptomatic disease in this age group mainly [10,27]. A wide spectrum of illness is associated with RSV infection, which rarely is asymptomatic. In young children, illness frequently begins with cough, nasal congestion, and fever. Otitis media is common. The primary manifestations of lower respiratory tract disease in infants are bronchiolitis and pneumonia. These two syndromes may be difficult to distinguish and may occur simultaneously [28]. In our population, 15% of hospitalized patients had bronchiolitis alone and 31.6% had either pneumonia or both. No significant difference in clinical presentation of RSV patients was observed among different age groups with cough (88.7%), wheezing (75.5%) and fever (64.5%) being the most common presenting symptom. Only one case presented with otitis media despite previous reports for being a presenting symptom in up to 17% of cases [10]. Apnea may be the presenting manifestation of RSV disease, particularly in preterm infants [28,29]. Apnea which was seen in 12.2% of our RSV patients with significant prevalence in the younger groups (P=0.01) has been reported as a complication in 10%-20% of hospitalized infants with RSV infection and is associated with sudden infant death syndrome [10]. It has been postulated that RSV alters the sensitivity of laryngeal chemo receptors and reinforces reflex apnea [28].
The most clinically significant difference in presentation among the compared age groups was the severity of respiratory distress. Ages less than 6 months were more likely to have moderate to severe distress (P= 0.014). This is attributed to the fact that younger ages more commonly present with lower respiratory tract infection including bronchiolitis and pneumonia (45%) compared to only 5% in children more than 2-5 years old [10].
Several environmental and other host factors have been reported to augment the risk of a more severe RSV infection [10]. These include younger age, male gender, gestational age, duration of breastfeeding, daycare attendance, tobacco exposure, presence of young children in the same household, in addition to underlying conditions [10]; all of which were compared between RSV and non-RSV groups here. RSV patients were younger, males, had less duration of breastfeeding, and were more likely to have a sick contact and a young sibling in the household. All other factors were found non contributory.
Limited testing and supportive management has been proposed by the American Academy of Pediatrics in 2006. Our study was conducted several years following the publication of these guidelines and so we sought to determine whether our management was impacted by them. Despite latest recommendations suggesting that only persistent SpO2< 90% is an indication for initiating supplemental oxygen [19], enrolled patients were actually supplemented with O2 when SpO2 dropped below 94% and thus 29.6% of RSV positive patients required oxygen. According to these same guidelines, many of the commonly used management modalities have not been shown to be effective in improving the clinical course of the illness. This includes the routine use of bronchodilators, corticosteroids, antibiotics, and chest radiography [19]. However, almost 70% of the RSV group and 63% of the non-RSV group required either inhaled β-adrenergic or αadrenergic or both during their hospital stay.
Almost 40% of enrolled patient received antibiotics and 20% received corticosteroids. But these patients included those previously asthmatic or with underlying lung disease and many might have developed secondary bacterial infections later which were not actually documented in our study.
As other studies have previously reported, our study suggests a more severe course for RSV infection when compared to the other causes. RSV positive patients had severe respiratory distress (P=0.001), required more oxygen (P<0.0001), were more likely to be admitted to intensive care unit (P<0.0001) and require mechanical ventilation (P=0.098). But so far, no effective anti-RSV vaccine or therapeutic modality is available. Several studies have focused on the development of RSV entry inhibitors targeting its F protein for the treatment of RSV infection but clinical trials were stopped because of unfavorable pharmaceutical properties of these compounds [29]. For this reason, various efforts have focused on the development of prophylactic RSV monoclonal antibodies. Palivizumab (Synagis®) has been FDA approved since 1998 [19]. The administration of prophylactic RSV antibodies has been shown to decrease severe disease [19]. The AAP recommends that palivizumab be considered for prophylaxis against RSV in children who have chronic lung disease or congenital heart disease that requires medical therapy, and are < 2 years old, as well as for infants born at 32 or fewer weeks' gestaion. Selected children born between 32 and 35 weeks' gestation may be considered for prophylaxis if there are other factors that make them more vulnerable to severe RSV disease including either daycare attendance or having a sibling less than 5 years of age [30]. Interestingly, only 3.8% of those who required intensive care were either preterm or had CLD or CHD, while the remaining 98.2% were previously healthy but with possible risk factors. This raises the question to whether the population that deserves prophylaxis should be expanded to include more groups of patients who are previously healthy but with certain risk factors.
Initiation and termination of immunoprophylaxis are dependent on seasonal variations of RSV. In the temperate climates, peak RSV activity typically occurs between November and March, whereas in equatorial countries, RSV seasonality patterns vary and may occur throughout the year [30]. In Lebanon, the outbreak season seems to start in November, peaks in December but continues throughout the winter and spring season and not ending till the end of July. We report RSV cases throughout the whole year with August being the only month with no reported cases hospitalized at our hospital.

Limitations of the Study
Despite the sufficient sample obtained during the study period, still it included hospitalized patients in only one tertiary center in Lebanon, and not several medical centers. The first period of the study was retrospective, so data collected at that time might have been incomplete or unavailable, but we relied mostly on calling back patients for missing data when contact was possible. Another setback in the study is that different nasopharyngeal wash swabs were collected by different doctors allowing thus inappropriate sampling techniques affecting the yield of the wash. Samples collected over the weekend might have been conserved for more than 24hrs before transfer to the laboratory, decreasing the yield of the sample. On the other hand, our study included almost 80% of all patients admitted since the availability of RSV rapid antigen detection and nasopharyngeal wash was used for all patients.

CONCLUSION
Respiratory Syncytial Virus is a significant burden among patients presenting with pneumonia and bronchiolitis and is associated with a more severe course. Previously healthy children are not at low risk for developing severe disease, so we suggest that immunoprophylaxis guidelines are worth receiving another review. As an effective vaccine against RSV is not yet available, parent education for preventive hygiene measures are more affordable and easy to perform. Awareness should also be raised in parents that what is a minor cold to them may cause a life-threatening illness in a young infant or a high risk child. Clinicians should emphasize on the use of RSV immunoprophylaxis among their patients as recommended by current guidelines keeping in mind each countries' special seasonal variation, until further updates are available.

RECOMMENDATIONS
Further studies are needed to determine a more accurate prevalence of Respiratory Syncytial Virus in Lebanon using polymerase chain reaction (PCR) for viral detection and including multiple medical centers and thus a larger sample.