SARS-CoV-2 Detection by RT-PCR

Molecular testing was performed as described previously (49 (link)). Briefly, RNA extraction was performed on respiratory specimens using the ZR viral kit (Zymo Research, Irvine, CA, USA) following the manufacturer´s instructions. Real-time reverse transcription-PCR (RT-PCR) was performed in a CFX96 thermocycler (Bio-Rad Laboratories, Hercules, CA, USA) using the iTaq universal probes one-step kit (Bio-Rad, Hercules, CA, USA) and specific SARS-CoV-2 primers/probe targeting the envelope and RNA-dependent RNA polymerase genes (50 ). In addition, amplification of the housekeeping human RNase P gene was included as an endogenous control for each sample using primers and probe reported elsewhere (51 (link)). The thermocycling conditions were 50°C for 10 min, 95°C for 3 min, 40 cycles of 95°C for 15 s, and 58°C for 30 s. Positive and negative (nontemplate) controls were included in each testing run. Samples were considered positive for SARS-CoV-2 when the cycle threshold (C_T) value was ≤38.