RSV in Adults

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I'm starting to wonder if some of the adult flu-like patients I saw recently were RSV -- they were negative for flu.

Locke, MD

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RSV IS AN ADULT VIRUS, TOO

LONDON—A new study confirms what experts have suspected for some time: Respiratory syncytial virus (RSV) is a significant contributor to influenza-like illness in community-dwelling adults.[1]

C. Zambon, PhD, and coworkers proved the association after analyzing 2,226 nasopharyngeal swabs from patients presenting with influenza-like illness (fever, cough, and respiratory tract illness) to general practices in England and Wales. “Influenza and RSV were prevalent in all age-groups,” noted Dr. Zambon. The findings refute the popular belief that RSV infection is clinically insignificant in adults. In addition, they raise a “substantial possibility” that the diagnosis of RSV infection and influenza may be confused, said the authors.

The nasopharyngeal swabs were collected at about a dozen general practices in England and Wales during the three winters between 1995 and 1998. The swabs were mailed to the study authors in virus transport medium for virologic surveillance and identification of influenza and RSV strains.

Dr. Zambon and colleagues found RSV (mainly type A) in 480 swabs and influenza virus in 709. Because the study was designed to look only for these viruses, no pathogens were identified in the other cases. The two viruses circulated simultaneously among all age-groups for 12 to 20 weeks each winter, but RSV generally appeared a few weeks before influenza virus did in the years studied.

RSV infection was quite common in adults. RSV infection rates among 45- to 64-year-old patients were 13%, 22%, and 19% during the three winters studied. The comparable rates for influenza were 29%, 38%, and 19%. The RSV strains detected in adults were similar to those found in children.

In children younger than 5 years, the RSV infection rates were 20%, 37%, and 41%; the rates of influenza were 32%, 33%, and 21%. Only in infants younger than 1 year was RSV always predominant.

These findings suggest that confusion may arise in both pediatric and adult patients—influenza may be misdiagnosed as RSV infection in children, just as RSV infection may be mistaken for influenza in adults.

If anything, the study may underestimate the burden of RSV-related disease in adults, said A. F. Simoes, MD, in an editorial.[2] Dr. Simoes, Associate Professor of Infectious Diseases in the Department of Pediatrics at the University of Colorado School of Medicine in Denver, explained that RSV is fragile and may have been destroyed when some swabs were mailed.

The observed prevalence of RSV infection in adults highlights the need to better distinguish RSV-related illness from influenza, said Dr. Zambon, head of the Respiratory Virus Unit in the Public Health Laboratory Service in London. Ongoing surveillance of both viruses is necessary, she added. If the high prevalence of RSV infection in adults is confirmed, it may be wise to consider RSV vaccination, which could be administered along with the flu shot. Also, specific antiviral therapies can be prescribed appropriately only in the context of good information on circulating viruses.

— Begany

References1. Zambon MC, Stockton JD, Clewley JP, Fleming DM. Contribution of influenza and respiratory syncytial virus to community cases of influenza-like illness: an observational study. Lancet. 2001;358:1410-1416. 2. Simoes EAF. Overlap between respiratory syncytial virus infection and influenza. Lancet. 2001;358: 1382-1383.