Declaration of interest:Role of the funding source: This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.Author contributions: YHL designed the study. YHL and CHL conducted the study and analyzed the data. YHL and YCC drafted the manuscript. All authors contributed to data analysis, drafting or revising the article, gave final approval of the version to be published, and agree to be accountable for all aspects of the work. Highlights The increased Google searches for "wash hands", rather than "face mask", reducing the speed of COVID-19 outbreak during the following three weeks among 21 countries. Google search for "wash hands" indicated not only the promotion of hand hygiene awareness but might also reflect the extent that people proactively engaged in hand washing. Google searches for "wash hands" provide real-time indicators for transmissionreduction policies and population health literacy in the early stage of the COVID-19 outbreak.3 AbstractThis study hypothesized that national population health literacy might reflect on their keywords searching. We applied Google searches for "wash hands" and "face mask"

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We show the possibility to generate bright and dark optical solitons based on bound-to-bound intersubband transitions in an asymmetric three-coupled quantum well structure. By presenting the concept of detuning management, we show that the bright optical soliton can evolve into a dark one by adiabatically changing the corresponding one-and two-photon detunings. With adjustable carrier frequencies within the terahertz regime, we also demonstrate numerically shape-recovered collisions of two solitons in our proposed quantum wells. The present investigation may provide research opportunities in nonlinear optical experiments and may have impact on the technology for the design of semiconductor devices.