Fig. 1

a RT-LAMP is initiated by adding internal primers (FIP or BIP) that annealed by Watson-Crick complementarity to regions (F2c or B2c) within the target RNA. The outer primer (F3 or B3) then hybridizes to its priming site (F3c or B3c) on the target RNA and initiates the formation of self-hybridizing loop structures by strand invasion of the DNA sequences already extended from the internal primers (FIP and BIP), resulting in a dumbbell structure. RT-LAMP process can be accelerated by loop primers (LF and LB). b Further, priming region of the fluorescently tagged probe (e.g. LB) is extended by a strand-displacing polymerase, and primer extension from the reverse primers then reads through the primer on the fluorescently tagged probe, displacing the probe that bears a quencher moiety. This separates the fluorescently tagged oligonucleotide from the quencher tagged probe, allowing the fluorescence to be observed in real-time and measured from fluorescently tagged probe that has been incorporated into RT-LAMP products