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Family Surveillance Study Sees Lack of Symptoms for Many Viral DNA Carriers

NEW YORK (GenomeWeb) – A study appearing online this week in the journal Clinical Infectious Diseases highlights the need for caution when clinically interpreting positive, PCR-based tests for viral infection.

As part of the "Better Identification of Germs-Longitudinal Viral Epidemiology," or BIG-LoVE, study, investigators at the University of Utah and BioFire Diagnostics used a PCR-based approach to screen for DNA corresponding to 16 different respiratory viruses in more than 100 individuals from 26 households over a year.

The team found that both respiratory virus DNA detection and infection symptoms were more common in households with children under the age of five years old, with young children often harboring viral DNA for longer-than-usual stretches of time. Even so, nearly half of instances in which viral DNA was detected were asymptomatic, particularly when bocaviruses and rhinoviruses were involved.

Based on these findings, the study's authors argued that the presence of viral DNA alone may not be enough to pin a mysterious illness on a respiratory virus in the clinic — especially when dealing with young children carrying DNA from frequently asymptomatic virus types such as rhinovirus.

"If a child comes into the emergency room with severe respiratory illness and tests positive for rhinovirus, it might be a smart idea for doctors to make sure they're not missing something else that could be the cause," co-first author Krow Ampofo, a pediatrics researcher at the University of Utah, said in a statement.

Ampofo and colleagues used BioFire Diagnostics' FilmArray PCR platform to do multiplexed screening for DNA from 16 respiratory viruses in nasal swabs collected weekly from 108 individuals in 26 households. Four homes contained just one individual, while the remaining households represented families of up to eight people.

From thousands of nasal swabs taken between August 2009 and August 2010, the researchers were able to track the respiratory viruses present in various households over time and look at how well the presence of positive PCR-based tests corresponded to participants' self-reported symptoms.

In particular, although viral DNA was detected 783 times, just 440 of these events coincided with infection symptoms.

Symptoms and viral DNA were more common in children who were five or younger, researchers reported, and youngsters were more prone to carrying viral DNA for three weeks or more.

Moreover, the investigators saw a jump in their ability to detect respiratory virus DNA in households with more and more children. For example, they estimated that individuals in childless homes experienced an average of three or four weeks of infection compared to 45 weeks in those from households containing six children.

On the whole, though, the team typically detected viral DNA for two weeks or less. And while symptoms were somewhat more common for those with coronavirus, human metapneumovirus, or influenza A virus in their nasal swab samples.

In contrast, those who tested positive by PCR for bocaviruses or rhinovirus — the virus most commonly found — often showed no sign of sickness.

In an editorial commentary set to appear in the same issue of Clinical Infectious Diseases, Washington University's Gregory Storch noted the such results "illustrate a fundamental limitation of pathogen-based diagnosis; namely, that detection of a pathogen does not prove that it is the cause of the patient's illness."

Along with a discussion of the study's strengths and weaknesses, Storch discussed some potential strategies for verifying potential viral infections, including host-response profiling.