The coronavirus pandemic has been causing damage to many nations, as public and private health systems deteriorate by the increasing demand. Some infected patients have culturable severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) even though not presenting any symptoms, and therefore, are probably able to transmit it. Correctly diagnosing and isolating infected patients is an important step towards preventing new infections. Current diagnostic methods rely mainly on reverse transcription quantitative polymerase chain reaction (RT-qPCR). Methods such as reverse transcription loop-mediated isothermal amplification (RT-LAMP) have risen as viable alternatives, as they are cheaper and require less infrastructure, they have the potential to be applied in low-resource scenarios and even at point-of-care. Here we report a colorimetric RT LAMP assay capable of detecting SARS-CoV-2 in ribonucleic acid (RNA) from saliva. In some cases, the test was able to detect viral RNA before symptom onset and even in a self-reported asymptomatic carrier. It had a limit of detection of 300 copies per reaction and showed a sensitivity of 80%, a specificity of 100%, a general accuracy of 99.59%, and a Cohen’s kappa of 0.887. The possibility of detecting positive cases even before the clinical manifestation shows great potential and can contribute to controlling the pandemic.

Dengue is one of the most prevalent infectious tropical diseases in the world, with high incidence in over 100 countries. Rapid and reliable diagnosis of dengue is of great importance for public health. To simplify molecular diagnostics, isothermal amplification techniques have recently emerged as an alternative to conventional methods of deoxyribonucleic acid (DNA) amplification. Here, we developed a one-step method for dengue virus detection from real sample based on RT-LAMP (reverse transcription-loop mediated isothermal amplification) in a disposable microdevice. The reaction was thermally controlled with a thermoblock for 15 min at 72 ºC. At the end of the incubation time, we either removed the solution for detection of fragments by gel electrophoresis or added DNA intercalator for visual detection on-chip. Our results demonstrated that it is possible to detect dengue virus through RT-LAMP directly from a serum sample, without previous ribonucleic acid (RNA) extraction. The success of RT-LAMP was confirmed in reactions initiated with 0.8 fg µL-1 of RNA, which represents 200 copies of RNA per µL. RT-LAMP in a polyester-toner (PeT) microdevice is a simple and inexpensive method that allows for rapid detection of dengue virus with high reliability and great potential for point-of-care applications.