Keywords
respiratory tract infections - children - viruses
Introduction
Respiratory tract infections (RTI) are among the most commonly seen infections across
the world, with the highest rate of morbidity. Viruses are known to be the primary
agent in 20 to 60% of these infections and mostly lead to upper RTIs. However, in
risk groups such as children, the elderly, those with underlying disorders, and patients
with immunosuppression, viruses could lead to serious infections by involving lower
respiratory tract, with high mortality.[1] Virus-induced RTIs are seen as significant public health challenges as they easily
lead to epidemics. Acute lower RTIs are reported to cause nearly four million deaths
annually, consisting mostly of children under 5 years of age.[2] In preschool period, each child experiences acute RTIs approximately five to eight
times per annum.[3] The most commonly detected viruses are respiratory syncytial virus (RSV), rhinovirus
(HRV), and influenza virus (INF).[4] The others may be listed as parainfluenza (PIV), adenovirus (AdV), and enteroviruses
(EV). Thanks to the developments in molecular diagnostic modalities, in recent years,
a number of tests have begun to be used to diagnose viral RTIs, and many novel viruses
leading to RTIs have been described, such as human metapneumoviruses (HMPV), severe
acute respiratory syndrome coronavirus which causes severe acute respiratory syndrome,
human coronavirus (HCoV), HCoV-NL63, HCoV-HKU1, human bocavirus (HBoV), and polyomaviruses
KI and WU. Among these agents, while INF, PIV, and RSV lead to epidemics in general,
viruses such as AdV, HCoV, and HRV give rise to endemic infections.[1]
The agents of acute RTIs, viruses, may exhibit different characteristics, depending
on geographical regions, seasonal differences, and diagnostic procedures. In warm
climates, an increase is observed in the incidences of RSV and INF, especially during
winter months. PIV 3 and PIV 1 in winter, PIV 2 at the initial of fall and winter,
EV during summer and fall months, and HRV in spring and winter are known to cause
infections at a higher rate, while AdVs could be the reason for infections within
each season.[1] PIV seasonality follows type-specific seasonal patterns, with PIV 1 circulating
in odd-numbered years and PIV 2 and PIV 3 circulating annually.[5]
Detection and classification of the common respiratory pathogens is impressively important
because of the fact that pathogens have potentially high morbidity and mortality rates.
Culture-based, antigen-based, and molecular techniques are currently used as diagnostic
methods. Among them, molecular methods have the potential for the highest sensitivity,
with assay turn-around times on the order of a few hours and foreseeable capability
to be run in a high-throughput batch process[6]
[7] In multiplex PCR assay (mPCR) with higher sensitivity, resulting in a shorter time
and one of the nucleic acid diagnostic methods developed to be used in the rapid diagnosis
of respiratory tract pathogens in clinical samples, multiple respiratory viruses can
be detected more than once in the same reaction using one clinical sample at the same
time.[8] Especially in children with lower RTI, agents can be diagnosed in exacerbations
such as febrile neutropenia, cystic fibrosis and chronic obstructive pulmonary disease,
and unnecessary use of antibiotics is prevented.[9] Because of providing rapid results, mPCR causes morbidity and mortality rates to
be decreased.[10]
In the present study designed retrospectively, it was aimed at investigating viral
agents leading to acute RTIs and their seasonal distributions in the province of Konya.
Materials and Methods
The Group of Patients and Clinical Samples
Prediagnosed with acute RTI between January 2013 and May 2015, children under the
age of 18 were included in the study. Nasopharyngeal swab samples obtained from a
total of 2,268 patients admitted to the hospital of Meram Medical School of Necmettin
Erbakan University and Ministry of Health Konya Training and Research Hospital were
investigated.
Method of mPCR
The nasopharyngeal swab samples obtained from the hospital of Meram Medical School
were investigated via Seeplex RV12 ACE Detection mPCR (Seegene, South Korea) while
the samples from Konya Training and Research Hospital were assessed using the system
by CLART PneumoVir (Genomica, Spain). Although only 12 viral agents such as HMPV,
AdV, HCoV; 229E/NL63, and OC43/HKU1, PIV 1, 2 and 3, INF A and B, RSV A and B, and
HRV A and B could be investigated by the system of Seeplex RV12 ACE Detection mPCR.
The system of CLART PneumoVir was capable of determining 18 viruses such as AdV, HMPV
A and B, PIV 1, 2, 3 and 4 (A and B subtypes), HRV, RSV A and B, HBoV, HCoV; 229E,
OC43, and NL63, EV, INF A (H7N9, H3N2, H1N1, H1N1/2009 subtypes), and INF B, and C
([Figs. 1], [2] and [3]).
Fig. 1 Patients' panel studied.
Fig. 2 Negative results of patients.
Fig. 3 Negative results of patients (influenza virus A [INF A] H3N2 positivity).
Results
Of the 2,268 samples investigated in the study, viruses were detected as agents in
1,320 (58.2%). The 1,320 positive samples were composed of 427 men (42.1%) and 588
women (57.9%). Positive number of viruses found in both kits were collected for use
in a table, and the most common viruses' rates were calculated according to these
numbers, among which, 27.9% were found to be RSV B, and this rate was, in turn, followed
by HRV (18.8%) and RSV A (17.8%) ([Table 1]).
Table 1
Distribution of viral agents leading to acute respiratory tract infections
|
Viruses
|
Number
|
Percentage (%)
|
|
RSV B
|
341
|
27.9
|
|
HRV
|
230
|
18.8
|
|
RSV A
|
217
|
17.8
|
|
HMPV
|
92
|
7.5
|
|
INF A (and subtypes)
|
91
|
7.5
|
|
AdV
|
88
|
7.2
|
|
INF B
|
60
|
4.9
|
|
PIV 3
|
58
|
4.8
|
|
HCoV
|
21
|
1.7
|
|
PIV 1
|
17
|
1.4
|
|
PIV 2
|
6
|
0.5
|
|
Total
|
1,221
|
100
|
Abbreviations: AdV, adenovirus; HCoV, human coronavirus; HMPV, human metapneumovirus;
HRV, human rhinovirus; INF A/B, influenza virus A/B; PIV 1/2/3, parainfluenza virus
1/2/3; RSV A/B, respiratory syncytial virus A/B.
Positivity was detected in agents more than once in 263 of 2,268 respiratory tract
swap samples in the study, and the findings presented in [Table 2].
Table 2
Distribution of viruses with positivity more than one
|
Viruses
|
Number
|
Percentage (%)
|
|
Double agents
|
236
|
89.8
|
|
Triple agents
|
18
|
6.8
|
|
Quaternary agents
|
9
|
3.4
|
|
Total
|
263
|
100
|
The most frequent concomitancy of double agents was observed in RSV B and HRV with
14% followed by RSV A and HRV with 6.8%, and PIV 3 and HRV with 5.9% ([Table 3]).
Table 3
Concomitancy of double agents with positivity
|
Viruses
|
Number
|
Percentage (%)
|
|
RSV B–HRV
|
33
|
14.0
|
|
RSV A–HRV
|
16
|
6.8
|
|
PIV 3–HRV
|
14
|
5.9
|
|
RSV A–RSV B
|
13
|
5.5
|
|
RSV B–HMPV
|
11
|
4.7
|
|
RSV A–HMPV
|
10
|
4.2
|
|
RSV A–INF B
|
10
|
4.2
|
|
Others
|
129
|
54.7
|
|
Total
|
236
|
100
|
Abbreviations: HMPV, human metapneumovirus; HRV, human rhinovirus; INF B, influenza
virus B; PIV 3, parainfluenza virus 3; RSV A/B, respiratory syncytial virus A/B.
Considering the distribution of samples with positivity to months, the positivity
was observed to be densely accumulated in January, February, March, and April ([Table 4]).
Table 4
Monthly distribution of viruses with positivity
|
Months
|
Number
|
Percentage (%)
|
|
January
|
223
|
16.9
|
|
February
|
217
|
16.4
|
|
March
|
265
|
20.2
|
|
April
|
158
|
12
|
|
May
|
97
|
7.3
|
|
June
|
108
|
8.2
|
|
July
|
57
|
4.3
|
|
August
|
44
|
3.3
|
|
September
|
41
|
3.1
|
|
October
|
36
|
2.7
|
|
November
|
30
|
2.3
|
|
December
|
44
|
3.3
|
|
Total
|
1,320
|
100
|
While RSV B and RSV A are encountered most in winter and spring months, HRV was determined
as an infectious agent in all seasons ([Table 5]).
Table 5
Distributions of most commonly detected viruses per month
|
Months
|
RSV B
|
HRV
|
RSV A
|
|
January
|
118
|
23
|
21
|
|
February
|
35
|
16
|
62
|
|
March
|
66
|
24
|
76
|
|
April
|
56
|
36
|
44
|
|
May
|
13
|
18
|
8
|
|
June
|
3
|
38
|
2
|
|
July
|
2
|
6
|
1
|
|
August
|
4
|
8
|
0
|
|
September
|
1
|
12
|
1
|
|
October
|
4
|
16
|
0
|
|
November
|
2
|
15
|
1
|
|
December
|
37
|
18
|
1
|
|
Total
|
341
|
230
|
217
|
Abbreviations: HRV, human rhinovirus; RSV A/B, respiratory syncytial virus A/B.
Discussion
Viral RTIs are a significant societal health challenge as they lead to long hospital
stays and even deaths, especially in children under the ages of 5. We consider that
knowing about the frequency and seasonal distribution of agents leading to viral RTIs
in this age segment sheds light on the diagnosis and vaccination for healthcare professionals.[11] In RTI-originated acute disorders, agents cannot be determined in general, and so
most of the agents determined are considered to be viral.[12] The effects witnessed on RTIs may display differences in terms of age segments,
seasons, underlying disorders, and geographical regions. According to their incidences,
however, RSV, INF, PIV 3, and AdV are reported as the agents ranking from highest
to lowest.[1]
In our study performed with mPCR assay, we determined viral agents of acute RTIs and
their percentages as RSV B (27.9%), HRV (18.8%), and RSV A (17.8%) ([Table 1]). In a similar study performed by Çiçek et al,[10] three most frequently encountered pathogens were defined as RSV (11.0%), HRV (5.6%),
and INF A (4.2%). One thousand one hundred and twenty-six eligible children were enrolled
in another prospective study from United States. A specific virus was identified in
61.0% of children, HMPV was identified in 9.0%, second to RSV (45%).[13]
Biçeret al,[14] however, reported RSV (32%) as the most frequent agent followed by AdV with 26.2%
and PIV with 19.4%. In another similar study performed by Akçalıet al,[15] RSV and HRV were reported as the most frequent agents with 61% and 35%, respectively.
In the study performed in children by Sancaklıet al[16], however, the most frequent agents were reported as HRV (26.4%) and RSV A-B (10.3%).
Another study also found that 48.5% of agents causing lower RTIs were viral, and 44%
of these originated from RSV.[17] In another retrospective study with 2,044 pediatric patients in Russia, the most
frequent RTI agents were identified as INFA (40%) and INFB (12%).[18] In our study the total rate of INF viruses is 12.4%. These rates may vary according
to region and year.
In the study by Akkaya et al,[19] RSV and HSV were emphasized as the most frequent viral agents in children. In the
study by Hatipoğluet al,[20] RSV (55.6%) and PIV (27.8%) were also found as the most frequent agents. In another
study, however, the most frequent agents were reported to be INF A (25%), HRV (20%),
and HMPV (10%).[21] As understood from these findings of studies conducted in different regions, different
results were reported.
Viral RTIs demonstrating seasonal differences lead to epidemics that could change
from year to year, especially in warm climates. RSVs are known to cause infections
most in winter months, while HRVs are known to do so throughout the year.[1]
[22] As consistent with those found in literature, similar results were obtained for
RSV and HRV in our study, as well. Considering the rates of coinfections in our study,
the concomitancy of RSV B-HRV was detected as 14%. Akçalıet al[15] report in their study that the concomitancy of RSV-HRV was found as the most widespread
reason for coinfection, as parallel to our findings. Again, in another study by Frobert
et al,[23] in children under the age of 2 in the intensive care unit, RSV (24.3%) was reported
to be the most frequently encountered agent in coinfections. Another prospective study
was performed with 772 hospitalized infants. Fifty-nine patients had coinfection with
RSV and HRV, RSV and AdV, INF and HRV, or AdV and HRV.[24] In two other studies, the coinfection rates of HRV-EV were found to be higher, compared
with other agents.[25]
[26] As seen in all these studies, why viruses lead to coinfections still remains unclear.[27]
The importance of respiratory viruses as the etiologic agent of RTIs in children was
verified in our study. In 58.2% of the children admitted to our hospitals with the
complaint of acute RTIs, the major pathogen was seen as virus. Our study summarizes
the clinical characteristics of viral agents that were detected in children with RTI.
The severity of diseases caused by RSV B, HRV, and RSV A were higher than other viruses.
Coinfections were detected in 19.9% of the patients, especially with some pathogens,
such as RSV, HRV, and PIV, whereas, AdV and HCoV were more commonly identified as
single infections. The presence of coinfections was not associated with increased
disease severity. RSV exhibited seasonal patterns; cases peaking over the rainy season
(December–April), and HRV were endemic throughout the year. It was concluded that
mPCR is beneficial for physicians to diagnose such viruses at an early stage. By the
early detection of respiratory viruses leading to seasonal epidemics, physicians'
approach to patients will become easier, and unnecessary use of antibiotics will be
prevented. Additionally, our study findings are intriguing in shedding light on studies
related to the development and application of vaccines.
