Viral agents of acute respiratory infections in young children in Kuala Lumpur

Bulletin ofthe World Health Organization, 60 (1): 137- 140 (1982) Viral agents of acute respiratory infections in young children in Kuala Lumpur S. B. ONG,' K. L. LAM,2 & S. K. LAM3 The results of this study indicate that the important viral agents associated with lower respiratory tract infections inyoung children are respiratory syncytial virus, rhinovirus, and parainfluenza virus, particularly in those under 2 years of age. This is in close agreement with studies done in temperate climates. Influenza A virus is seasonal andplays an impor- tant role in upper respiratory tract infections in older children. Respiratory diseases are a major cause of morbidity and mortality all over the world and it is estimated that about 2.2 million deaths from acute respiratory infections (ARI) occur throughout the world every year. In children ARI account for up to 20% of all deaths in some countries, the highest mortality being in infants below 1 year of age. Most data on acute respiratory diseases come from studies conducted in temperate areas; data from the tropics and subtropics are rather scanty. A WHO Scientific Group on Viral Respiratory Diseases held in Geneva in 1979 (17) recommended increased surveil- lance because of the great public health importance of acute respiratory infections, especially in developing countries. This paper reports a study on children with ARI seen at or admitted to the University Hospital in Kuala Lumpur, Malaysia. The aim of the study was to determine the viral etiological agents of ARI in urban children. MATERIALS AND METHODS Study subjects and specimens A single specimen of nasopharyngeal secretion was collected, over a period of 30 months, from each of 180 children of up to 10 years of age, using disposable sterile mucus extractors. The subjects included chil- dren admitted to the paediatric wards and those treated as outpatients at the University Hospital, Kuala Lumpur. The children were selected for the ' Lecturer, Department of Medical Microbiology, University of Malaya, Kuala Lumpur, Malaysia. 2 Professor, Department of Paediatrics, University of Malaya, Kuala Lumpur, Malaysia. 3 Associate Professor, Department of Medical Microbiology, University of Malaya, Kuala Lumpur, Malaysia. study if: (a) they had signs and symptoms of acute respiratory illness with or without skin rash; (b) no antibiotics had been administered to them recently; (c) their parents agreed to their participation in the study; and (d) they themselves were cooperative in the collection of specimens. Immediately after collec- tion each specimen was sent to the laboratory for virus isolation. Virus isolation Each nasopharyngeal specimen was mixed with tryptose phosphate broth containing per litre, 5 g of gelatin, 400 units of penicillin, 400 ug of strepto- mycin, and 200 ug of nystatin. This was centrifuged and the supernatant inoculated into tissue cultures. The types of tissue culture and the methods used for the isolation of viruses have been described elsewhere (14). Haemadsorbing agents in primary monkey kidney cells were identified by the haemagglutination-inhi- bition test for influenza viruses and by complement- fixation tests for parainfluenza viruses types 1, 2, and 3. Presumptive identifications of adenoviruses and respiratory syncytial (RS) virus were made by obser- ving the appearance of cytopathic changes in HEp-2 cells and confirmed by complement-fixation using specific immune sera. Rhinoviruses were distinguished from entero- viruses by their sensitivity in the acid lability test at pH 3. Enteroviruses were further typed by neutraliz- ation using immune serum pools (8). RESULTS Of the 180 children studied, 59 had upper respira- tory tract infection (URTI) and 121 had lower respira- 4155 137- S. B. ONG ET AL. Table 1. Association between clinical diagnosis and virus isolated Clinical diagnosis Virus Upper Lower respiratory tract infection Total respiratory tract infection Bronchitis Bronchiolitis Pneumonia Whooping cough Influenza A 5 - - 2 - 7 Influenza B 1 1 - - 1 3 Parainfluenza 1 - - 3 - 4 RS virus 4 - 5 8 2 19 Adenovirus 1 - - 1 - 2 Rhinovirus 2 2 1 1 2 8 Echovirus - - 1 1 - 2 RS virus + rhinovirus - - 1 4 - 5 RS virus + parainfluenza - - 1 - 1 2 Total specimens positive 14 3 9 20 6 52 Total specimens tested 59 14 21 71 1 5 180 Percentage isolation 23.7 21.4 42.9 28.2 40.0 28.9 tory tract infection (LRTI). Viruses were isolated and rhinoviruses, and about 85%o of the RS virus from 52 of the 180 specimens collected (28.9%o). specimens were found to be associated with LRTI. While only one virus was isolated from each of 45 of Five of the 6 specimens yielding parainfluenza viruses the 52 virus-positive specimens, 7 yielded two viral and 11 of the 13 with rhinoviruses were also associ- agents each (Table 1). ated with LRTI. Five out of 7 influenza A virusiso- The most common viruses isolated were RS virus lates were from patients with URTI. Specimens from Table 2. Number of isolates in each age group' Virus 0-5 6-11 12-23 2-3 3-5 5-10 months months months years years years (48) (36) (43) (14) (22) (17) Influenza A 2 - 1 1 2 1 Influenza B 1 - 1 - - 1 Parainfluenza 1 1 1 - 1 RSvirus 8 4 5 - 1 1 Adenovirus 1 1 - - - Rhinovirus 2 - 3 - 1 2 Echovirus - 2 - - - RS + rhinovirus 1 1 2 - - 1 RS + parainfluenza 2 - - - Total 18 7 15 1 5 6 a The figures in parenthesis indicate number of patients in each age group. I138 VIRAL AGENTS OF ACUTE RESPIRATORY INFECTIONS 139 children with bronchiolitis gave the highest rate of virus isolation (42.9%o). Six of the 7 children who yielded 2 viruses each were less than 2 years of age and all 7 had LRTI. RS virus was isolated in all 7; in 5 cases this was associated with rhinovirus and in 2 with parainfluenza virus. Table 2 shows the distribution of viral agents among the various age groups. Of the 180 children examined, 127 (71 o) were aged 0-23 months. Among these children, the frequency of virus iso- lation was 31.5%o. RS virus and rhinoviruses were the two most common pathogens recovered from the younger age group, the rate of their recovery being highest in infants less than 6 months of age and decreasing in the older age groups. Parainfluenza viruses were either type 1 or 3 and were recovered mainly in children less than 2 years of age with LRTI. The 2 echoviruses recovered in this study were from infants aged 6- 11 months. DISCUSSION About 29% of the specimens examined in this study were positive for viral agents as compared with 48%o in an earlier study of specimens obtained from a private paediatric clinic (13). The higher recovery rate from the latter study may have been due to better specimen collection by a single person and also to the fact that more acute cases are usually seen in private practice. However, the rate reported in this study is comparable with those obtained by other workers (6, 14). The results of the present study showed RS virus to be the most important viral pathogen in the early months of life and that it was associated with lower respiratory tract infections. This is in agreement with a number of previous studies (1-3, 5) and also con- curs with data obtained in a serological study of Malaysian children (12). The association of rhinoviruses with LRTI is of interest and has been observed by other workers (4, 7). Parainfluenza viruses may also play an important role in the younger age group. Adenoviruses and echoviruses play a lesser role in respiratory infections in children. Influenza viruses are associated with upper respiratory tract infection during epidemics. The occurrence of multiple viral infections in infants and children has been reported previously (9-11, 15, 16, 18) and in this study RS virus was present with either rhinovirus or parainfluenza virus. ACKNOWLEDGEMENTS The authors are grateful for the cooperation of the medical and nursing staff of the Department of Paediatrics, University Hospital, Kuala Lumpur, in the collection of clinical specimens. We also thank Mr Saw Teik Leong for his technical assistance. RtSUMP- AGENTS VIRAUX DES INFECTIONS AIGUES DES VOIES RESPIRATOIRES CHEZ LES JEUNES ENFANTS A KUALA LUMPUR On a cherche a identifier les virus responsables d'infec- tions aigues des voies respiratoires chez 180 petits citadins soignes a l'H8pital universitaire de Kuala Lumpur, en Malaisie. Des virus ont e isoles de 52 des 180 echantillons collectes (soit 28.9%). Les agents qui ont e le plus fre- quemment identifies etaient le virus respiratoire syncytial, le rhinovirus et le virus parainfluenza. Quelque 85% des 6chantillons contenant les virus respiratoire syncytial prove- naient d'enfants de moins de 2 ans atteints d'infections des voies respiratoires inferieures. Ces resultats rejoignent ceux d'6tudes effectu&es dans des climats temper6s. Le virus grippal A a ete trouve associe A des infections des voies respi- ratoires superieures survenues au cours d'epidemies chez des enfants plus ages. REFERENCES 1. BEEM, M. ET AL. New Englandjournal ofmedicine, 263: 523 - 530 (1960). 2. 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