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To the Editors:Human parechoviruses (HPeV) infections are mainly prevalent in young children with mild gastroenteritis and respiratory infections whereas meningitis and neonatal sepsis are less frequent.1 To date, 16 serotypes (HPeV-1 to 16) have been described. In Spain, there are no previously published studies of their epidemiology and clinical associations with respiratory diseases because HPeV have not yet been included in routine viral diagnosis. This study attempts to investigate the involvement of HPeV in pediatric acute respiratory infections.A total of 529 nasopharyngeal swabs collected from January 1 to December 31, 2010, were included. Specimens were from hospitalized children less than 15 years old with acute respiratory infection at the Severo Ochoa Hospital in Madrid who had previously been tested by polymerase chain reaction for 14 respiratory viruses, including respiratory syncytial virus (RSV), adenovirus (AdV), human bocavirus (HBoV), human metapneumovirus (hMPV), rhinovirus (RV), enterovirus (EV), parainfluenza virus (PIV 1–4), coronavirus (CoV-229E and CoV-OC43) and influenza viruses (Flu A, B, C). HPeV detection was carried out using a specific reverse transcriptase polymerase chain reaction in 5′-no coding region of the genome,2 and typing was by nucleotide phylogenetic analysis of sequences from the VP1/VP3 region (GenBank accession numbers JX946706-JX946725).Targeted respiratory viruses were detected in 365 (69%) of the 529 samples analyzed. The remaining 164 samples were negative for all viruses (31%). Of the 365 positive samples, 102 (28%) were codetections with 2 or more viruses. HPeV were detected in 19 (3.6%) of the total samples analyzed. The incidence was similar to that observed for hMPV (4%) in the same population and higher than observed for Flu and EV (1.7% for both). However, it was significantly lower than observed for RV, RSV, HBoV, AdV and PIV (33%, 17%, 11%, 10% and 9%, respectively) (P < 0.001). In 17 of 19 (89%) HpeV-positive samples, other respiratory viruses were codetected. The frequency of HPeV codetection was substantially higher than for other respiratory viruses (RV, RSV, PIV, hMPV and EV) (P < 0.05). Furthermore, codetection frequencies with RSV and AdV were significantly higher than for HPeV-negative cases (P < 0.05).HPeV were detected in children aged between 3 months and 4.5 years (mean age, 1.2 years). HPeV type 1b was the most frequent (12/19, 63%), followed by HPeV-6 (6/19, 32%) and HPeV-3 (1/19, 5%). The mean age of HPeV-1–infected children was significantly lower (7.25 ± standard deviation 2.59 months) than in patients infected by HPeV-6 (27.83 ± standard deviation 16.15 months) (P = 0.00042).Most of the HPeV (74%) were detected in the autumn and the early winter, with another minor peak in March. Regarding clinical disease association, 11 (58%) HPeV-positive cases were diagnosed as recurrent wheezing, 5 (26%) as bronchiolitis, 1 as pneumonia, 1 as upper respiratory infection and diarrhea and 1 as a febrile syndrome. The 2 patients in whom HPeV was detected alone (HPeV-1 and HPeV-6) were diagnosed with upper respiratory infection plus diarrhea and recurrent wheezing, respectively.HPeV has associated with upper respiratory tract infections, bronchiolitis and pneumonia.1 To date, only 3 large series of more than 3000 respiratory samples were reported, showing a detection frequency of less than 2%.2–4 In agreement with previous studies, there was low incidence of HPeV (3.6%) mainly affecting children between 3 months and 5 years. HPeV-1 is the most frequently identified genotype, although HPeV-6 is also significantly detected in respiratory specimens. Our data also showed HPeV-1–infected children to be significantly younger than those with HPeV-6.