Fig. 3: Visual detection of respiratory RNA viruses.
a, Cross-reaction test of SARS-CoV-2, SARS-CoV and MERS-CoV. Left: sequences of coronavirus N genes targeted by MARVE. Middle: heat map recording the absorbance at 560 nm using each TEprobe for profiling the three coronaviruses. Right: the corresponding visual detection panel for the three coronaviruses. b, Visual detection of seven influenza virus subtypes. c, Working principle of the origami paper. TEprobes, urease and urea/phenol red are loaded on page 2, 3 and 4, respectively. MARVE reactions are initiated by sequential paper-folding. d, Paper-based detection of respiratory viral RNAs. GAR is the proportion of regions with a green component in the detection sites. e–g, Sensitivity estimation of paper-based detection by targeting the N gene (e,g) or the E gene (f) of SARS-CoV-2. The red line in g indicates the threshold for classification. MARVE yielded positive results for all 21 replicates of samples, with 400 copies per μl of SARS-CoV-2 pseudovirus. h, Detection of respiratory RNA viruses spiked in throat swab samples. Photographs (left) and GAR values (right) of origami papers testing samples with SARS-CoV-2, SARS-CoV or MERS-CoV. SARS-CoV and MERS-CoV were detected by targeting their N genes. The presence of the human RNase P gene indicates successful sampling and preservation of throat swab samples. Urea cleavage reaction proceeded for 20 min in a and b. The concentration of each virus was 30,000 copies per μl in a and b, and 2,400 copies per μl in d and h. Data in b and d are mean ± s.d. (n = 3). Data in e and f are from 6 replicates. Data in g are mean ± s.d. (n = 21). Statistical significance in e, f and g was determined by a two-tailed Welch’s t-test: **P < 0.01, ***P < 0.001, ****P < 0.0001.
