Due to worldwide occurrence, substantial morbidity and mortality rates, respiratory viral infection which swiftly and easily spread, pose a serious public health problem (1) . Human metapneumovirus (hMPV) is one of the etiological agents of acute respiratory tract infections (AR-TIs) which can infect people in all age groups (2) . It induces clinical symptoms ranging from upper to lower respiratory tract illnesses such as bronchiolitis, bronchitis and pneumonia (3) (4) (5) . In 2001, HMPV was identified in samples from children with respiratory tract disease for the first time (6) . In addition, it is a new member of the family paramyxoviridae, subfamily pneumovirus, genus metapneumovirus (7) . RSV is one of the most important respiratory pathogens of childhood, with detection rates reaching 70-85% in hospitalized infants during seasonal winter epidemics worldwide (1, 8) . RSV causes severe lower respiratory infections like bronchiolitis or pneumonia in infants and young children (9) . Coinfection of hMPV with RSV in infants has been suggested to be a factor that influences the severity of bronchiolitis (9) . Phylogenetically, RSV is the closest human virus related to hMPV, and the clinical manifestations of hMPV may share an overlapping spectrum with RSV, so that these two viruses cannot be distinguished by clinical manifestations (4, 7, 9, 10) . RSV and hMPV might have similar seasonal patterns, so co-infection is possible (6, 9) . This report describes a case who did not have the respiratory sign and symptoms, while was actually infected with RSV and hMPV simultaneously. and mouth since 4 d ago. In spite of treating with antipyretics, fever still was persistent. On physical examination, the vital signs were as follow: respiration, 22 breath/min; pulse, 104 beats/min and temperature, 38˚ C. Cardiac, abdominal, neurological and respiratory findings were normal. Laboratory findings were as follows: WBC count, 9.9×10 3 /µl; RBC, 3.77×10 6 /µl; Hb, 10.6 g/dl; Hct, 34.5%; PLT, 443×10 3 /µl; ESR, 90; CRP, +1; Wright/Widal and salmonella Para A/B, Typhi D were negative. Stool exam was normal. In the abdominal sonography, there was no problem and chest X ray was also normal. According to the findings, possible diagnosis was Kawasaki syndrome and treatment with IVIG, aspirin and acetaminophen was started. After one day, fever was resolved but dry cough started at the day four of the admission. Because of the history of contact with chickens and possibility of H5N1, throat swab specimen of the patient was collected and sent to the National Influenza Center in Tehran university of Medical Sciences for influenza surveillance. The specimen was tested for Influenza virus types and subtypes by real time PCR assay using CDC procedure, CDC Real-Time RT-PCR (r.RT-PCR) protocol for detection and characterization of influenza virus (version.2007), but the result was negative. Subsequently, as a part of a project, the specimen was tested for RSV and hMPV by heminested multiplex PCR and parainfluenza viruses type 1-4 by hemi-nested multiplex PCR (11) , and adenovirus by hemi-nested PCR (12) . In our surprise positive results for RSV and hMPV were observed without any special respiratory sign and symptoms. The test was repeated and the results were confirmed again. The nucleotide sequence of the PCR product of the detected hMPV (the M gene fragment) was submitted to GenBank (Accession no. GQ219792).
In the present study, we demonstrated the possibility to detect dual infection which caused by RSV and hMPV. Due to the lack of sensitivity of conventional methods detection of co-infections with different respiratory viruses had been un-derestimated (13) . Severe RSV bronchiolitis in small patient series had been recognized because of co-infection with other viral pathogens (14) . Some previous studies have lighted up increased clinical severity in case of dual infection caused by RSV and hMPV (8, 9) . Greensill et al. observed a 70% co-infection rate with HMPV and RSV and a 90% co-infection rate among intubated infants with hMPV and RSV admitted to their PICU (8) . Although Greensill et al. did not include an appropriate control group in their study, these findings suggest that co-infection with both hMPV and RSV is common and that together the two viruses may contribute to increase the severity of disease (9, 14) . Whereas in other reports hMPV did not contribute to the severity of RSV infection (15, 16) . The basis of the pathogenesis of severe RSV disease is multifactorial. Since severe RSV disease may develop in apparently healthy children, known host risk factors cannot completely account for instances of severe illness. Preexisting or maternally acquired immunity, innate immunity, viral factors and genotypes and environment all likely contribute to disease pathogenesis. We detected co-infection of hMPV and RSV in Kawasaki patient without special respiratory sign and symptoms, we could not find the patient to follow up her and study more about the immunity status and other possibilities of this scenario. More investigation is suggested specially on Kawasaki patients to detect the viral pathogens.
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