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

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Abstract

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.

Introduction

Approximately 200 million episodes of acute respiratory tract illnesses occur in adults in the United States yearly, resulting in 75 million physician visits and over $1 billion in medical care costs (Garibaldi, 1985). Most of these illnesses are viral in nature and with the exception of influenza, a specific diagnosis is rarely made. Recently, reverse transcription polymerase chain reaction (RT-PCR) has replaced less sensitive techniques such as viral culture and retrospective methods such as serology to investigate the cause of viral respiratory disease in adults (Boivin et al., 2002, Falsey et al., 2002, Freymuth et al., 2004). RT-PCR is a powerful tool that allows the detection of minute quantities of viral RNA or DNA. Because of the extreme sensitivity of these techniques, questions have arisen as to the interpretation of a positive result. Does the finding of viral RNA indicate active or recent infection or could it represent 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. Therefore, we evaluated the nasal secretions from adults with and without respiratory illnesses by nested, one-tube RT-PCR for RSV and hMPV during a 3-month period when both viruses were expected to be prevalent in the community.

Section snippets

Methods

The study was conducted between January 6 and April 15, 2004 in Rochester, NY, a period during which RSV and hMPV activity was expected based on previous epidemiologic studies. Adults over age 18 years were recruited at three locations: a general medical clinic at Rochester General Hospital, physicians’ offices at a large health maintenance organization, and an after-hours urgent care center. The University of Rochester Institutional Review Board approved the study and all subjects signed

Results

One hundred forty-six cases and 158 control subjects were recruited during the study period. Cases and controls were well matched for age, sex, underlying diseases, living conditions, smoking status, and exposure to children (Table 1).

Of the 146 ill subjects tested, 17 (11.6%) tested positive for RSV and 5 (3.4%) were positive for hMPV. Of the 158 control subjects without respiratory illnesses, one person was RT-PCR positive for RSV and none tested positive for hMPV. The rates of RT-PCR

Discussion

RSV and hMPV RNA was detected by nested RT-PCR at a significantly higher rate in ill subjects compared to those without respiratory complaints. During a period when both viruses were circulating in the community, RSV RNA was detected only in one and hMPV RNA was not identified in any control subjects. Thus, this data strengthens the causal link between the detection of viral RNA and respiratory illness. Transient colonization of healthy adults with hMPV or RSV does not appear to be a common

Acknowledgements

The authors wish to thank Gloria Andolina and Maria Formica for technical assistance and Cynthia Serve for transcription.

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