Abstract
BackgroundHuman metapneumovirus (HMPV) is established as one of the causative agents of respiratory tract infections. To date, there are limited reports that describe the effect of HMPV genotypes and/or viral load on disease pathogenesis in adults. This study aims to determine the role of HMPV genetic diversity and nasopharyngeal viral load on symptom severity in outpatient adults with acute respiratory tract infections.MethodsSeverity of common cold symptoms of patients from a teaching hospital was assessed by a four-category scale and summed to obtain the total symptom severity score (TSSS). Association between the fusion and glycoprotein genes diversity, viral load (quantified using an improved RT-qPCR assay), and symptom severity were analyzed using bivariate and linear regression analyses.ResultsAmong 81/3706 HMPV-positive patients, there were no significant differences in terms of demographics, number of days elapsed between symptom onset and clinic visit, respiratory symptoms manifestation and severity between different HMPV genotypes/sub-lineages. Surprisingly, elderly patients (≥65 years old) had lower severity of symptoms (indicated by TSSS) than young and middle age adults (p = 0.008). Nasopharyngeal viral load did not correlate with nor predict symptom severity of HMPV infection. Interestingly, at 3–5 days after symptom onset, genotype A-infected patients had higher viral load compared to genotype B (4.4 vs. 3.3 log10 RNA copies/μl) (p = 0.003).ConclusionsOverall, HMPV genetic diversity and viral load did not impact symptom severity in adults with acute respiratory tract infections. Differences in viral load dynamics over time between genotypes may have important implications on viral transmission.
Highlights
Human metapneumovirus (HMPV) is established as one of the causative agents of respiratory tract infections
Our analyses showed that nasopharyngeal viral load could not predict the severity of symptoms caused by HMPV infection, as well as the total symptom severity score (TSSS) scoring system could not predict the amount of viral load in the patient, both variables were found to be not correlated in this study
This study investigated the impact of HMPV genetic diversity and viral load on symptom severity in an adult outpatient cohort presenting with acute respiratory tract symptoms, in which both factors were found not to be associated with a more severe symptom outcome
Summary
Human metapneumovirus (HMPV) is established as one of the causative agents of respiratory tract infections. This study aims to determine the role of HMPV genetic diversity and nasopharyngeal viral load on symptom severity in outpatient adults with acute respiratory tract infections. HMPV infections are commonly associated with mild respiratory symptoms, but severe cough, bronchiolitis and pneumonia have been reported, sometimes accompanied by high fever, myalgia and vomiting [2]. Previous reports had attempted to associate the genetic diversity of HMPV, which are classified as genotypes A and B (with further classification into sub-lineages - A1, A2a, A2b, B1 and B2) [4] with disease severity [5,6,7]. Apart from viral genetic diversity, HMPV viral load was recognized as a risk factor associated with more severe disease outcome leading to hospitalization [11, 12]
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