Common etiological viral agents of respiratory infections include adenoviruses (ADV), influenza types A and B (Flu A and B), parainfluenza types 1, 2, and 3 (PIV1, 2, 3),and respiratory syncytial virus (RSV). 1-4 These viruses are responsible for a spectrum of acute upper and lower respiratory tract disease. In children, the elderly and other immunocompromised groups, respiratory viruses can cause more serious clinical complications, such as croup, bronchiolitis, and pneumonia, which often require hospitalization. 5,6 Virus isolation by cell culture and direct immunofluorescent antibody assay (DFA) staining with monoclonal antibodies are two of the most commonly used laboratory techniques for detecting respiratory viruses. Both these methods have significant limitations in sensitivity and specificity. DFA detection is more rapid but less sensitive than viral culture, and results may be affected by specimen quality (ie, presence of intact, infected cells), virus type, and interpretation of a positive result, which is subjective and requires a great deal of technical skill. 2,7-10 DFA is also unable to detect minor variations in amino acid sequence on envelope or capsid proteins. 11 Viral culture is still considered the "gold standard" for respiratory virus detection, but is limited by a prolonged result turnaround time (ie, 2 days to 1 week) and is dependent on stringent specimen transport and storage conditions to preserve the infectivity of the virus. 9,[12][13][14][15] Although the combination of both these techniques can provide an increase in the number of positive results, a significant proportion of specimens still remain negative, despite clinical suspicion of viral infection. 8 Several studies have shown that polymerase chain reaction (PCR) amplification can resolve the intrinsic limitations associated with traditional diagnostic techniques by combining increased sensitivity, specificity, and rapid result turnaround time. 16,17 Also, PCR results are not dependent on infectious virus or viable cells. However, Supported by Royal Children's Hospital Foundation grants RA921-006 and I922-034 which were sponsored by the Woolworth's "Care for Kids" campaign.

Nose-throat swab specimens, in combination with sensitive molecular testing, are a less invasive diagnostic respiratory specimen with adequate sensitivity for use in the clinic and hospital outpatient settings and large-scale community studies through parent collection. For children who present to a hospital in which an avian or pandemic strain of influenza virus is reasonably part of the differential diagnosis, nasopharyngeal aspirates or a similar collection technique (eg, nasal washes) should continue to be used.

The recent description of the respiratory pathogen human metapneumovirus (hMPV) has highlighted a deficiency in current diagnostic techniques for viral agents associated with acute lower respiratory tract infections. We describe two novel approaches to the detection of viral RNA by use of reverse transcriptase PCR (RT-PCR). The PCR products were identified after capture onto a solid-phase medium by hybridization with a sequence-specific, biotinylated oligonucleotide probe. The assay was applied to the screening of 329 nasopharyngeal aspirates sampled from patients suffering from respiratory tract disease. These samples were negative for other common microbial causes of respiratory tract disease. We were able to detect hMPV sequences in 32 (9.7%) samples collected from Australian patients during 2001. To further reduce result turnaround times we designed a fluorogenic TaqMan oligoprobe and combined it with the existing primers for use on the LightCycler platform. The real-time RT-PCR proved to be highly reproducible and detected hMPV in an additional 6 out of 62 samples (9.6%) tested during the comparison of the two diagnostic approaches. We found the real-time RT-PCR to be the test of choice for future investigation of samples for hMPV due to its speed, reproducibility, specificity, and sensitivity.

The age-specific immunity to human parvovirus infection was estimated in Victoria, Australia using prospectively collected samples from the Royal Children's Hospital, the Royal Women's Hospital and the Australian Red Cross Blood Service and from sera stored at the Victorian Infectious Diseases Reference Laboratory (VIDRL). All testing was performed at VIDRL using a commercial enzyme-linked immunosorbent assay (Biotrin). Of the 824 sera tested, 28% of those drawn from people aged 0-9 years contained protective antibodies to human parvovirus. This rose to 51% in the next decade of life. There was then a slow rise to about 78% immunity over 50 years of age. An analysis of all requests for parvovirus serology at VIDRL from 1992 to 1998 suggested that parvovirus tended to occur in 4-year cycles, with 2 epidemic years followed by 2 endemic years. A review of published reports of parvovirus immunity suggested that parvovirus infection may be more common, with a correspondingly higher proportion of the community immune, in temperate as opposed to tropical countries.

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