Figure 1. Respiratory pathogen load in UPT and in corresponding nasal swab, as captured by Cq values measured with the respiratory panel (for EV/RV, HCoV-229E, Influenza A, Influenza B, Streptococcus pneumoniae and PIV-3) or with the SARS-CoV-2 RT-PCR (for SARS-CoV-2). Cq values for each measurement are plotted as dots, and corresponding measurements in the same patient are connected with lines. Different respiratory pathogens are identified with colours as shown in the legend.
To assess the effect of prolonged storage of the UPT on room temperature, a large number of UPTs were collected from an EV/RV positive patient within the same day (aiming to obtain equal viral loads in all UPTs) and stored in a paper box at room temperature. Extraction and testing of a standardized UPT aliquot was performed after 1, 2, 3 , 4, 6 and 8 weeks. EV/RV Cq values were 15.9 (wk 1), 19.5 (wk 2), 16.3 (wk 3), 22.5 (wk 4), 25.2 (wk 6) and 21.2 (wk 8), showing that although Cq values fluctuated the pathogen was readily detectable in UPTs up to 2 months after sample collection.
One patient was followed over the course of a COVID-19 infection, from the time of first symptom up to complete symptom resolution, with UPT, nasal swabs in UTM and Ag-RDTs being collected daily (Fig 2). SARS-CoV-2 was detectable in UPT as of the start of symptoms, whereas the Ag-RDT only turned positive on Day 4. For as long as the Ag-RDT remained positive, SARS-CoV-2 was also detectable in UPT. In the nasal swab, SARS-CoV-2 was still detectable after Ag-RDTs turned negative, and remained detectable up to the last symptomatic day.