Detection of Human Bocavirus mRNA in Respiratory Secretions Correlates with High Viral Load and Concurrent Diarrhea

Human bocavirus (HBoV) is a parvovirus recently identified in association with acute respiratory infections (ARI). Despite its worldwide occurrence, little is known on the pathogenesis of HBoV infections. In addition, few systematic studies of HBoV in ARI have been conducted in Latin America. Therefore, in order to test whether active viral replication of human bocavirus is associated with respiratory diseases and to understand the clinical impact of this virus in patients with these diseases, we performed a 3-year retrospective hospital-based study of HBoV in outpatients and inpatients with symptoms of Acute Respiratory Infections (ARI) in Brazil. Nasopharyngeal aspirates (NPAs) from 1015 patients with respiratory symptoms were tested for HBoV DNA by PCR. All samples positive for HBoV were tested by PCR for all other respiratory viruses, had HBoV viral loads determined by quantitative real time PCR and, when possible, were tested by RT-PCR for HBoV VP1 mRNA, as evidence of active viral replication. HBoV was detected in 4.8% of patients, with annual rates of 10.0%, 3.0% and 3.0% in 2005, 2006 and 2007, respectively. The range of respiratory symptoms was similar between HBoV-positive and HBoV-negative ARI patients. However, a higher rate of diarrhea was observed in HBoV-positive patients. High HBoV viral loads (>108 copies/mL) and diarrhea were significantly more frequent in patients with exclusive infection by HBoV and in patients with detection of HBoV VP1 mRNA than in patients with viral co-infection, detected in 72.9% of patients with HBoV. In summary, our data demonstrated that active HBoV replication was detected in a small percentage of patients with ARI and was correlated with concurrent diarrhea and lack of other viral co-infections

Respiratory DNA viruses are undetectable in nasopharyngeal secretions from adenotonsillectomized children

<div><p>Respiratory viruses are frequently detected in association with chronic tonsillar hypertrophy in the absence of symptoms of acute respiratory infection (ARI). The present analysis was done in follow-up to a previous clinical study done by this same group. Nasopharyngeal washes (NPWs) were obtained from 83 of 120 individuals at variable times post adenotonsillectomy, in the absence of ARI symptoms. A look back at virus detection results in NPWs from the same 83 individuals at the time of tonsillectomy revealed that 73.5% (61/83) were positive for one or more viruses. The overall frequency of respiratory virus detection in post-tonsillectomy NPWs was 58.8%. Rhinovirus (RV) was the agent most frequently detected, in 38 of 83 subjects (45.8%), followed by enterovirus in 7 (8.4%), human metapneumovirus in 6 (7.2%), human respiratory syncytial virus in 3 (3.6%) and human coronavirus in 1 (1.2%). Remarkably, there was no detection of adenovirus (HAdV) or human bocavirus (HBoV) in asymptomatic individuals in follow-up of adenotonsillectomy. In keeping with persistence of respiratory DNA viruses in human tonsils, tonsillectomy significantly reduces asymptomatic shedding of HAdV and HBoV in NPWs.</p></div