Analysis of Viral Load in Children Infected with Human Metapneumovirus

OBJECTIVE Human metapneumovirus (hMPV) is a respiratory pathogen responsible for disease and subsequent hospitalizations in young children around the world. The disease pathology, including how viral load correlates with respiratory disease severity, remains unclear. This study investigated the correlation between viral load and clinical characteristics of hMPV infections. METHODS Nasopharyngeal aspirate (NPA) samples collected from 18 infants hospitalized for lower respiratory tract infections (LRTIs) in winter were tested for hMPV by reverse transcriptase polymerase chain reaction (RT-PCR) and real-time RT-PCR. Their NPA samples were collected every-other-day to monitor changes in hMPV viral load during hospitalization. Also all these 18 patients were monitored to characterize clinically their illness. FINDINGS hMPV load was not correlated with infection severity (P=0.5, 0.9, 0.5). In contrast, the log(10) of hMPV viral load was significantly different between those lasted for 6-11 days and those for less than 5 days (P=0.01), also the significant difference was shown between those of 6-11 days duration and those of more than 11 days (P=0.006), but there was no significant difference between those lasted for less than 5 days and those for more than 11 days (P=0.4). Additionally, high hMPV viral shedding occured between 6 and 11days. CONCLUSION hMPV load was significantly correlated with the course of illness. The association between hMPV viral load and the course of disease suggested that hMPV is an important pathogen in lower respiratory tract infection in children. But hMPV did not always lead to more severe respiratory illness.