Arch Pediatr Infect Dis. 2015 July; 3(3): e21581. DOI: 10.5812/pedinfect.21581v2 Published online 2015 July 13. Research Article The Prevalence of Human Metapneumovirus and Respiratory Syncytial Virus and Coinfection With Both in Hospitalized Children With Acute Respiratory Infection in South of Iran Afagh Moattari 1,* ; Soheila Aleyasin 2 ; Amir Emami 1,3 ; Mahzad Fyruzi 3 ; Neda Pirbonyeh 1 1 Department of Bacteriology and Virology, School of Medicine, Shiraz University of Medical Sciences, Shiraz, IR Iran 2 Department of Pediatrics, Shiraz University of Medical Sciences, Shiraz, IR Iran 3 Shiraz Burn Research Center, Shiraz University of Medical Sciences, Shiraz, IR Iran *Corresponding author: Afagh Moattari, Department of Bacteriology and Virology, School of Medicine, Shiraz University of Medical Sciences, Shiraz, IR Iran. Tel: +98-9173136844, E-mail: moattaria@sums.ac.ir Received: June 28, 2014; Revised: May 9, 2015; Accepted: May 12, 2015 Background: Viral infections are the most frequent causes of morbidity and mortality due to respiratory dysfunction worldwide, especially in children under five years of age. Several studies have reported the association of human metapneumovirus (hMPV) and respiratory syncytial virus (RSV) with acute respiratory infection. Objectives: The present study aimed to investigate the prevalence of hMPV, RSV, and their coinfection in children with respiratory symptoms hospitalized in Shiraz City, Fars Province, Iran. The study also attempted to determine the association between asthma and wheezing with hMPV, RSV, and coinfection with both in studied children. Patients and Methods: The study included 280 younger than five years old children with non-influenza infection that were hospitalized for respiratory infection from 2011 to 2013. Nasopharyngeal swabs were collected from patients and tested for RSV and hMPV with reverse transcriptase polymerase chain reaction. Results: The hMPV and RSV were detected in 44 (15.7%) and 84 (30.0%) samples, respectively. Coinfection with both viruses was found in ten patients (3.57%). The incidence of hMPV and RSV infections were observed in children younger than one year old. Infections occurred predominantly from October to April. The most common clinical symptoms were bronchiolitis, wheezing, and cough. Conclusions: Infection with hMPV and RSV are most frequent infections among pediatric patients with respiratory tract symptoms. Coinfection with these viruses may exacerbate the clinical symptoms and increase hospitalization rates, especially in children younger than one year old. Keywords: Respiratory Syncytial Virus; Human Metapneumovirus; Asthma; Wheezing Copyright © 2015, Pediartric Infections Research Center. This is an open-access article distributed under the terms of the Creative Commons Attribution-NonCom- mercial 4.0 International License (http://creativecommons.org/licenses/by-nc/4.0/) which permits copy and redistribute the material just in noncommercial us- ages, provided the original work is properly cited. 1. Background Different studies showed that wide range of viruses such as Adenovirus, Coronavirus, Influenza viruses, re- spiratory syncytial viruses (RSV), and human parainflu- enza viruses are associated with respiratory disease in humans (1). Over the last decade, van den Hoogen et al. reported the isolation of a novel virus in young children with acute respiratory tract infections (2, 3). This virus was classified in the metapneumovirus genus of the sub- family Pneumovirus, family Paramyxoviridae of the order mononegavirales and was given the provisional name of human-metapneumovirus (hMPV), which can infect people in all age groups (3-5). Since then this virus with other respiratory tract viruses, a new human polyomavi- rus (bocavirus) (6, 7), and two new coronavirus types (5, 8) are introduced as the main causes of respiratory tract infections in human, especially children. In recent studies, viruses including influenza viruses and RSV have been frequently detected in samples ob- tained from patients with lower respiratory tract infec- tion, especially in pediatric patients. It has been showed that viruses, alone or together with pathogenic bacteria, are responsible for respiratory tract infections where vi- ral infections are the most substantial causes of morbid- ity and mortality in respiratory dysfunction, especially in children under five years old (1, 9). Viruses are potential etiologic agents of pneumonia, wheezing, and asthma in children. The association of hMPV with asthma exacerbation has been reported in several recent studies (9, 10). In addi- tion, wheezing is a common symptom manifested in chil- dren infected with hMPV (9, 11). These studies have shown that infection with hMPV, which was identified in upper and lower respiratory tracts of patients, can lead to bron- chiolitis, bronchitis, and pneumonia (3, 11). RSV is another important respiratory pathogen of child- hood (70 - 85% of cases) during winter epidemics, espe-