The newly identified 2019-nCoV (SARS-CoV-2) RNA virus has caused over 80,000 laboratory-confirmed human infections in China (as of Mar. 1st, 2020), and is now becoming a global epidemic issue. As a result, highly sensitive, reliable and field-deployable methods to detect 2019-nCoV that can be developed in a shortest possible time are urgently needed. In this work, we introduce whole-course encapsulated and ultrasensitive field detection methods against 2019-nCoV gene. We applied isothermal exponential amplification methods via reverse transcription plus subsequent enzymatic recombinase amplification (ERA), a modified recombinase polymerase amplification (RPA), to amplify trace level of 2019-nCoV RNA. We designed both exo FRET probe and nfo affinity probe for easy detection of the amplified nucleic acids. These methods can be developed within a few days and as low as 0.32 aM (i.e. 0.32×10-18 M) of RNA can be reliably detected.