The virological features and clinical findings associated with the new human metapneumovirus (HMPV) were examined retrospectively in Canadian patients hospitalized for various respiratory conditions since 1993. Thirty-eight previously unidentified respiratory viruses isolated from rhesus monkey kindey (LLC-MK2) cells were found to be positive for HMPV by reverse-transcription polymerase chain reaction, and those strains clustered in 2 phylogenetic groups. Children aged <5 years and elderly subjects aged >65 years represented 35.1% and 45.9% of the HMPV-infected cases, respectively. In hospitalized children, the most frequent diagnoses were pneumonitis (66.7%) and bronchiolitis (58.3%), whereas bronchitis and/or bronchospasm (60%) and pneumonitis (40%) were most commonly seen in elderly subjects. Of the 15 patients with pneumonitis, 4 (26.7%) had immunosuppressive conditions and 6 (40%) were infants aged <15 months. These findings suggest that HMPV can be associated with severe lower-respiratory-tract infections in very young children, the elderly, and immunocompromised patients.

The human Metapneumovirus (HMPV), a new member of the Paramyxoviridae family, has been recently associated with respiratory tract infections in young children. We report the case of a young, immunocompromised child who had severe lower respiratory tract infections during two consecutive winter seasons caused by genetically distinct HMPV strains.

Event-related potentials (ERPs) were recorded during a visual two-choice reaction time (RT) task in attention-deficit hyperactivity disorder (ADHD) and control boys selected using strict inclusion and exclusion criteria. No group differences were found in mean RT and correct responses. Although early occipital ERPs were not affected in the ADHD group, the peak latency of early anterior ERPs (N1, P1, N2) was significantly delayed. ADHD showed a larger effect of stimulus type on the frontal negativity (N530) and the posterior late negativity (nSW) and a smaller effect of stimulus type on anterior N2 and posterior P3b amplitude. The development of N530 and P450 amplitude across blocks of five trials was analyzed using orthogonal polynomial trend analysis of variance software. In the control group, P450 amplitude to "frequent" stimuli reduced across blocks. In the ADHD group, N530 amplitude increased for "rare" stimuli across blocks. It is suggested that the ADHD group showed a lack of automatization of the categorization process with increasing time on task for which they compensated by controlled attentional processes.