The team, including researchers from University Medical Centres in Amsterdam, Bochum and Freiberg, determined the incidence of this novel virus in a sample of children under three years old with such respiratory infections. Nine hundred and forty nine samples of nasopharyngeal secretions were collected from both hospitalized patients and outpatients in four different regions of Germany. The study found that forty-nine samples (5.2%) were positive for the virus HCoV-NL63 overall, with a greater incidence in outpatients (7.9%) than hospitalized patients (3.2%). Co-infection with two other viruses also known to be prominent in the cause of LRTIs, was also frequently observed.
The researchers also investigated the occurrence of HCoV-NL63 in cases of respiratory disease where no other virus could be detected. Here, a strong relationship with the clinical symptoms associated with croup was apparent: 43% of the HCoV-NL63 positive patients with high HCoV-NL63 load and absence of co-infection had croup, compared with 6% of HCoV-NL63 negative patients. Previous studies have reported trends in croup, such as the relative susceptibility of boys to the disease, its peak occurrence in the second year of life and its predominance in late autumn and earlier winter, that are matched by patterns of HCoV-NL63 occurrence.
This systematic association of croup with HCoV-NL63 is particularly timel y as the newly identified virus has spread worldwide, reported in Australia, Japan, the US and Canada. The study will also contribute towards the clarification of the viral causes of lower respiratory tract infections generally; causes that have not always been apparent despite the frequency of such infections amongst children.