Flowchart of the EV-D68 testing algorithm. Presumptive EV-D68: EV-D68 PCR cycle threshold (CT) values at least 4 cycles lower than the HRV CT (for HRV-positive samples) or any EV-D68 CT value (for HRV negative samples). Proven EV-D68: confirmed by sequencing. RV, respiratory viruses.