e8 | www.pidj.com The Pediatric Infectious Disease Journal •  Volume 32, Number 1, January 2013 ORIGINAL STUDIES Background: Viruses are detected in most hospitalized children admit- ted for acute respiratory infections. Etiologic understanding is needed to improve clinical management and prevention, particularly in resource-lim- ited tropical countries. Methods: A 3-year prospective descriptive study was conducted among Cambodian children admitted to 2 provincial hospitals for acute lower res- piratory tract infection. Molecular detection for 18 viral pathogens using multiplex polymerase chain reaction/reverse transcription polymerase chain reactions was performed. Results: We enrolled 1006 children less than 5 years of age of whom 423 (42%), 428 (42%) and 155 (16%) had pneumonia, bronchiolitis and unclas- sified lower respiratory tract infections, respectively. Of the 551 (55%) with documented viral infection, a single virus was detected in 491 (89%), including rhinovirus (n = 169; 34%), respiratory syncytial virus (n = 167; 34%), parainfluenza virus (n = 40; 8%), human metapneumovirus (n = 39; 8%), influenza virus (n = 31; 6%), bocavirus (n = 16; 3%), adenovirus (n = 15; 3%), coronavirus (n = 9; 2%) and enterovirus (n = 5; 1%). Coinfections with multiple viruses were detected in 6% (2 viruses detected in 59 cases; 3 viruses detected in 1 case). Conclusion: Similar to other tropical countries, rhinovirus and respiratory syncytial virus were the principal viral pathogens detected among children hospitalized for lower tract respiratory infection in Cambodia. Key Words: pneumonia, virus, respiratory pathogens, multiplex polymer- ase chain reaction, pediatric, Cambodia (Pediatr Infect Dis J 2013;32: e8–e13) A cute viral lower respiratory tract infection (LRTI) is a lead- ing cause of hospitalization for infants and young children in developed countries and is a major cause of death in developing countries. 1–3 Better understanding of the full spectrum of respira- tory viruses causing LRTI in hospitalized children is essential for improving therapeutic strategies and prioritizing diagnostic efforts. Epidemiologic surveillance of LRTI appears to be particularly cru- cial in South East Asia where emerging novel viral agents such as H5N1 influenza and SARS-coronavirus (hCoV) and pandemic A (H1N1) influenza caused serious public health concerns. Although some studies reported the distribution of respiratory viruses caus- ing LRTI among children in neighboring countries, 4–6 no similar data are available in Cambodia. This study describes viral etiolo- gies, clinical and epidemiologic characteristics among children less than 5 years of age admitted for LRTI in 2 hospitals in Cambodia. METHODS Study Design A 3-year prospective study was performed in 2 provincial hospitals located in Takeo Province and Kampong Cham Province, Cambodia, respectively. These 2 hospitals represent typical second- ary hospitals of rural Cambodia, with limited laboratory facilities. The climate of Cambodia is tropical, characterized by a dry season from November to May and a wet season from June to October. Two third of the annual rainfall occurs during the wet season, dur- ing which humidity levels are higher and extremes of temperature are greater. Individuals less than 5 years of age were eligible for inclu- sion if admitted for an LRTI with an onset of illness less than 14 days before hospitalization. LRTI was diagnosed on clinical grounds with symptoms of cough or respiratory distress associated with tachypnea, with or without fever. Excluded were patients who were discharged from the hospital in the previous 21 days, newborns who never left the hospital, patients with uncomplicated upper respiratory illness such as rhinitis, sinusitis and otitis media, patients with proven or sus- pected tuberculosis or HIV or patients with proven or suspected noninfectious respiratory symptoms. Demographic and clinical data were documented using standardized case report forms. Clinical symptoms were assessed by a clinician and documented using a standardized questionnaire. Data collection included age, onset of symptoms before admission, rectal temperature at admission, hypoxia, presence of fast breath- ing, administration of antibiotics, status at discharge and length of hospital stay. Hypoxia was defined by transcutaneous oxygen saturation <92%. Fast breathing was defined by a respiratory rate ≥60 breaths/min if aged <2 months; ≥50 breaths/min if aged 2–11 months; and ≥40 breaths/min if aged 1–5 years. Physicians were unaware of diagnostic results for respiratory viruses during data collection. A chest radiograph (CXR) was ordered within 48 hours of admission. CXR was read by an expert panel and determined to be consistent with pneumonia (ie, condensation, nodules, alveolar or interstitial syndrome). Bronchiolitis was defined as acute respiratory infection in patients less than 2 years of age presenting with wheezing or crepitation and without radiographic evidence of pneumonia. LRTI other than pneumonia or bronchiolitis was defined as unclassified LRTI (ULRTI). Copyright © 2012 by Lippincott Williams & Wilkins ISSN: 0891-3668/12/3201-00e8 DOI: 10.1097/INF.0b013e31826fd40d Acute Viral Lower Respiratory Tract Infections in Cambodian  Children: Clinical and Epidemiologic Characteristics Gilles Guerrier, MD,* Sophie Goyet, MPH,* Eak Tep Chheng, MD,† Blandine Rammaert, MD,*‡ Laurence Borand, PharmD,* Vantha Te, MD,§ Patrich Lorn Try, MD,¶|| Rith Sareth, PharmD,* Philippe Cavailler, MD,* Charles Mayaud, MD, PhD,¶|| Bertrand Guillard, MD,* Sirenda Vong, MD, PhD,* Philippe Buchy, PhD,* and Arnaud Tarantola, MD* Accepted for publication July 24, 2012. From the *Institut Pasteur in Cambodia, Phnom Penh, Cambodia; †National Pediatric hospital, Phnom Penh, Cambodia; ‡Université Paris-Descartes, Sorbonne Paris Cité, Hôpital Necker-Enfants Malades, Service des Maladies Infectieuses et Tropicales, APHP, Centre d’Infectiologie Necker-Pasteur, Institut Hospitalo-Universitaire Imagine, Paris, France; §Takeo Provincial hospital, Takeo, Cambodia; ¶Kampong Cham provincial hospital, Kampong Cham, Cambodia; and ||Hôpital Tenon, Paris, France. This study was supported by Surveillance and Investigation of Epidemic Situa- tions in Southeast Asia (SISEA) project. The authors have no other funding or conflicts of interest to disclose. Address for correspondence: Gilles Guerrier, MD, Institut Pasteur in Cambodia, Phnom Penh 1200, Cambodia. E-mail: guerriergilles@gmail.com.