There is paucity of studies on etiology of acute respiratory infections (ARI) in infants. The objective of this study is to document incidence and etiology of ARI in infants, their seasonal variability and association of clinical profile with etiology.
A birth cohort was followed for the first year of life; for each episode of ARI, nasopharyngeal aspirates were collected to identify the causative respiratory virus(es) using multiplex real-time polymerase chain reaction assay. For lower respiratory tract infections blood culture, serum procalcitonin, serum antibodies to Mycoplasma and Chlamydia and urinary Streptococcus pneumoniae antigen were also assayed.
A total of 503 ARI episodes were documented in 310 infants for an incidence rate of 1.8 episodes per infant per year. Of these, samples were processed in 395 episodes (upper respiratory tract infection: 377; lower respiratory tract infection: 18). One or more viruses were detected in 250 (63.3%) episodes and viral coinfections in 72 (18.2%) episodes. Rhinovirus was the most common virus [105 (42%)] followed by respiratory syncytial virus [50 (20%)], parainfluenza virus [42 (16.8%)] and coronavirus [44 (17.6%)]. In lower respiratory tract infections, viral infections were detected in 12 (66.7%) episodes, bacterial infections in 17 (94.4%) episodes and mixed bacterial–viral infections in 8 (44.4%) episodes. Peak incidence of viruses was observed during February–March and September–November. There was no significant difference in symptom duration with virus types.
In this cohort of infants, ARI incidence was 1.8 episodes per year per infant; 95% were upper respiratory tract infections. Viruses were identified in 63.3% episodes, and the most common viruses detected were rhinovirus, respiratory syncytial virus and parainfluenza virus.
From the *Department of Pediatrics, All India Institute of Medical Sciences, New Delhi, India; †Department of Biotechnology, Vaccine and Infectious Disease Research Center, Translational Health Science and Technology Institute (THSTI), Faridabad, India; and ‡Department of Microbiology, All India Institute of Medical Sciences, New Delhi, India.
Accepted for publication September 27, 2016.
This study was funded by the Department of Biotechnology, Government of India.
The authors have no conflicts of interest to disclose.
Address for correspondence: Sushil K. Kabra, MD, Pediatric Pulmonology Division, Department of Pediatrics, All India Institute of Medical Sciences, Ansari Nagar, New Delhi 110029, India. E-mail: email@example.com.