Emerging respiratory agents: new viruses for old diseases?

Abstract

The recent advances in molecular technology have enabled the detection of several new viral agents in specimens collected from the human respiratory tract. Human metapneumovirus was first described in 2001, and is a significant respiratory pathogen, particularly of children. Following the identification of severe acute respiratory syndrome (SARS) associated coronavirus, two other newly detected coronaviruses, NL63 and HKU1, have been linked to respiratory disease in humans. However, identifying a new virus as the causative agent of a specific disease is difficult, and ideally would involve satisfying Koch's postulates. The recently described human bocavirus and polyomaviruses KI and WU have been detected in samples collected from humans with acute respiratory infection, but as yet, have not been conclusively proven to be agents of human disease. We review the new viral agents that have been detected in respiratory samples since 2001, and examine their contribution as agents of human disease.

Fig. 1

(A) VIDISCA method. Schematic overview of the stages incorporated in the performance of the VIDISCA method (adapted from van der Hoek et al., 2004). (B) Random PCR. Primer 1 with a unique 5′-end and degenerate 3′-end sequence is used in a first round PCR. The degenerate segment binds to template sequences that occur stochastically throughout the viral genome, and primer extension occurs with T4 polymerase. Double-stranded DNA is formed containing unique sequences on each strand. Primer 2 hybridizes to the unique sequence and is used for amplification of fragments of the viral template DNA (adapted from Stang et al., 2005). (C) High throughput sequencing. Randomly amplified PCR products are cloned into a suitable plasmid vector, and subsequently sequenced.