Efforts to mitigate the COVID-19 crisis revealed that fast, accurate, and scalable testing is crucial for curbing the current impact and that of future pandemics. We propose an optical method for directly imaging unlabeled viral particles and using deep learning for detection and classification. An ultrasensitive interferometric method was used to image four virus types with nanoscale optical pathlength sensitivity. Pairing these data with fluorescence images for ground truth, we trained semantic segmentation models based on U-Net, a particular type of convolutional neural network. The trained network was applied to classify the viruses from the interferometric images only, containing simultaneously SARS-CoV-2, H1N1 (influenza-A), HAdV (adenovirus), and ZIKV (Zika). Remarkably, due to the nanoscale sensitivity in the input data, the neural network was able to identify SARS-CoV-2 vs. the other viruses with 960 ms, on a common graphic processing unit. This approach of directly imaging unlabeled viral particles may provide an extremely fast test, of less than a minute per patient. As the imaging instrument operates on regular glass slides, we envision this method as potentially testing on patient breath condensates.The necessary high throughput can be achieved by translating concepts from digital pathology, where a microscope can scan hundreds of slides automatically.One Sentence Summary This work proposes a rapid (lt;1 min.), label-free testing method for SARS-CoV-2 detection, using quantitative phase imaging and deep learning.Competing Interest StatementG.P. and C.B-P. have financial interests in Phi Optics Inc., a company that manufactures quantitative phase imaging instruments for biomedical applications.
Original languageEnglish (US)
PublisherCold Spring Harbor Laboratory Press
Number of pages28
StateIn preparation - Dec 15 2020

Publication series

PublisherCold Spring Harbor Laboratory Press


  • Novel coronavirus
  • COVID-19
  • severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)
  • Pandemic
  • 2019-nCoV


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