COVID-19 testing as sufficient as needed is essential for healthcare workers, patients, and authorities to make informed decisions to confront and eventually defeat severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Currently, diagnosis of COVID-19 relies on quantitative reverse-transcription PCR, which is low-throughput, laborious, and often false-negative, making it overwhelmingly challenging to meet testing needs even in industrialized countries. Here we propose a new strategy, which employs a modified loop-mediated isothermal amplification (LAMP) assay, a simple procedure requiring no sophisticated instruments, to index and amplify viral genes from individual specimens, of which the products are readily available for construction of multiplexed libraries for next-generation sequencing. Our strategy would allow precise diagnosis of thousands of specimens in 1-2 days with significantly lower operating expenses. Furthermore, this strategy will make it possible for patients to collect, process, and mail their own samples to facilities for a quick, reliable diagnosis at a population scale.