Page 47 - Epidemiological studies on tuberculosis control and respiratory viruses

samples of upper airways by PCR in the community could provide information on the background prevalence of upper respiratory viruses and might shed light on the size of this diagnostic issue at population level.
Main conclusions and implications
In chapter 6, nasopharyngeal samples of upper airways were investigated by multiplex RT-PCR collected during the influenza seasons of 2011, 2012 and 2013, from participants in an adult population-based cohort study, reflecting the general population, and from adult outpatients and inpatients of the hospital, serving the catchment area of the cohort study population. This provided the opportunity to study the relative distribution and viral loads of respiratory viruses among adult populations by approximated illness severity, based on symptom status and health care use.
Chapter 6 showed that among virus-positive individuals, influenza virus A (InfA) and
human metapneumovirus (hMPV) were overrepresented in the hospital population,
while rhinovirus (RV), human coronavirus (hCoV) and human bocavirus (hBoV) were
more common in the general population, confirming differences in pathogenicity
between these respiratory viruses. Combined, InfA and hMPV contributed to 35% of
detected viruses in the hospital population versus only 9% in the general population,
suggesting that causality can be implied if detected in patients presenting with acute
respiratory illness. However, this was less straightforward for viruses such as RV,
hCoV and hBoV, which together represented 42% of detected viruses in the hospital
population, indicating that positive PCR results of such viruses should be interpreted
with caution if detected in patients with respiratory symptoms seeking health care.
Additional interpretative parameters for such viruses circulating in the community
could make a significant contribution to the clinical interpretation of diagnostic
results in hospitalized patients. Viral load might represent one such parameter. 7 However, in chapter 6, a significant relation between levels of viral replication and
approximated illness severity, was found only for InfA, while these correlations were less clear for RV, hCoV, for which additional parameters are most needed.
Although we found a relation between InfA viral load and approximated illness severity, mere PCR detection of InfA was already a strong indicator of the causality between infection and symptoms, suggesting that viral load as an additional interpretative parameter is of little added value to qualitative PCR results. Nevertheless, InfA viral
General Discussion
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