Detection of respiratory syncytial virus and human metapneumovirus by reverse transcription polymerase chain reaction in adults with and without respiratory illness

Background: Reverse transcription polymerase chain reaction (RT-PCR) is a powerful tool that allows the detection of minute quantities of viral RNA. Because of the sensitivity of these assays it is possible that the finding of viral RNA indicates not only active infection but also transient colonization or residual nucleic acid from a distant infection. Respiratory syncytial virus (RSV) and human metapneumovirus (hMPV) are two viruses for which RT-PCR is now frequently used for diagnosis in adult disease. Objective: We evaluated nasal secretions from adults with and without respiratory illnesses by nested, one-tube RT-PCR for RSV and hMPV to determine if rates of detectable RNA were significantly higher among ill subjects compared to controls suggesting a causal relationship with respiratory illness. Methods: Adults presenting to a healthcare provider with complaints of respiratory illness were recruited as "cases" and those visiting for non-respiratory complaints were recruited as "controls". Subjects were enrolled during a 3-month period (January to April) when both viruses were expected to be prevalent in the community. Nasal swab samples were obtained and subjected to one-tube nested RT-PCR for RSV and hMPV. Results: Of 146 ill subjects, 17 (11.6%) tested positive for RSV and 5 (3.4%) were positive for hMPV. Of the 158 control subjects, one was RT-PCR positive for RSV and none tested positive for hMPV. The rates of RT-PCR positive cases compared to controls were significantly different for RSV (p < .0001) and hMPV (p < .02). Subjects remained RSV RT-PCR positive on average until day 7.1 +/- 2.8 of symptoms with a range of 3-10 days. No subject had a positive swab on days 14, 21 or 28. Conclusion: Asymptomatic carriage of RSV or hMPV is uncommon. RT-PCR should be a useful method for the diagnosis of these viral illnesses in adults. (C) 2005 Elsevier B.V. All rights reserved.